Category: Week 12

Released July 26, 2024

Welcome to Week 12 for the 2024 growing season! This week includes:
• Weather synopsis (for July 8-14, 2024)
• Weather synopsis (for July 14-20, 2024)
• Aphids in field crops
• Canola flower midge scouting
• Bertha armyworm
• Diamondback moth
• Lygus bug monitoring
• Grasshopper
• Provincial insect pest report links
• Crop report links
• Previous posts

Catch Monday’s Insect of the Week for Week 13 – What’s eating my crop? Swede midge

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Questions or problems accessing the contents of this Weekly Update? Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.

Weather synopsis (for July 8-14, 2024)

This week’s weather summary was kindly provided by the Prairie Crop Disease Monitoring Network (PCDMN).

Last week (July 8-14, 2024), average cumulative 7 day rainfall was 5 mm (Figure 1) and was well below the previous week (July 1-7) that experienced an average cumulative rainfall value of 16.7 mm. The average 30 day (June 14 – July 14) temperature was 0.5° C warmer than long term average values. Most of the prairies reported 30 day rainfall amounts ranging from normal to above normal. A region from Saskatoon to Oyen has had uncharacteristically high rainfall; Kindersley and Oyen had greater than 250 % of normal precipitation (Figure 2). Driest conditions were observed near Edmonton and the western areas of the Peace River region. Since April 1, the 2024 growing season average temperatures have been 0.5° C greater than climate normal values. Most of the prairies have had above normal to above normal (157 %) rainfall (Figure 3).

Figure 1. 7 day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 8-14, 2024.
Figure 2. 30 day percent of normal rain (%) observed across the Canadian prairies for the period of June 14-July 14, 2024.
Figure 3. Growing season percent of normal rain %) observed across the Canadian prairies for the period of April 1 – July 14, 2024.

Soil moisture conditions (top 5 cm) continue to be driest for the eastern and Peace River regions of Alberta and southern regions of Saskatchewan (Figure 4). Soil moisture values were greatest for Manitoba and the Parkland region of Saskatchewan.

Figure 4. 7 day average saturated soil moisture (% soil moisture for the surface layer, <5 cm depth) for the period of July 8-14, 2024.

Growing degree day (GDD) dynamic maps for the Canadian prairies for Base 5 ºC and Base 10 ºC (April 1-July 15, 2024) can be viewed by clicking the hyperlinks. Over the past 7 days (to July 21, 2024), the lowest temperatures recorded across the Canadian prairies ranged from -22 to 10 °C while the highest temperatures observed ranged from 4 to 33 °C. In terms of precipitation across the Canadian prairies, review the growing season accumulated precipitation (April 1-July 21, 2024), the growing season percent of average precipitation (April 1-July 21, 2024), and the past 7 days (as of July 21, 2024). Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

Growers can bookmark the AAFC Maps of Current Agroclimate Conditions for the growing season. Historical weather data can be accessed at the AAFC Drought Watch Historical website, Environment and Climate Change Canada’s Historical Data website, or your provincial weather network. The AAFC Canadian Drought Monitor also provides geospatial maps updated monthly.

Weather synopsis (for July 14-20, 2024)

This week’s weather summary was kindly provided by the Prairie Crop Disease Monitoring Network (PCDMN).

Relative to climate normal values, average temperatures have increased over the past four weeks. The 7 day average temperature for July 14-20, 2024 was 20.5 °C and was 3.3 °C warmer than normal. Warmest temperatures were observed for northern regions of the Alberta Peace River region, eastern regions of Alberta, and southern regions of Saskatchewan (Figure 1).

Figure 1. Seven day average temperature (°C) observed across the Canadian prairies for the period of July 14-20, 2024.

The 30 day (June 21-July 20) average temperature (18.4 °C) was 2 °C warmer than average (Figure 2). Growing season (April 1 – July 20) average temperatures were 0.7 °C warmer than average (Figures 3 and 4, respectively).

Figure 2. 30-day average temperature (°C) observed across the Canadian prairies for the period of June 21 – July 20, 2024.
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 – July 20, 2024.
Figure 4. Growing season average temperature anomalies (°C) observed across the Canadian prairies for the period of April 1 – July 20, 2024.

Last week (July 14-20, 2024) average cumulative 7 day rainfall was 4.4 mm (Figure 5). Most of the prairies reported 30 day rainfall amounts that were normal to above normal (Figure 6). Rainfall amounts have been above normal for the majority of Manitoba and normal to below normal for most of Alberta. Driest conditions were observed near Edmonton and the western areas of the Peace River region. Rainfall values (June 21-July 20) have been highly variable across Saskatchewan. Growing season (April 1 – July 20) precipitation has been above normal to above normal (147 %) rain (Figure 7).

Figure 5. 7 day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 14-20, 2024.
Figure 6. 30 day percent of normal rain (%) observed across the Canadian prairies for the period of June 21 – July 20, 2024.
Figure 7. Growing season percent of normal rain (%) observed across the Canadian prairies for the period of April 1 – July 20, 2024.

Soil moisture conditions (top 5 cm) continue to be driest for eastern and Peace River regions of Alberta and southern regions of Saskatchewan (Figure 8). Soil moisture values were greatest for Manitoba and the Parkland region of Saskatchewan.

Figure 8. 7 day average saturated soil moisture (%) for the surface layer (<5cm)) for the period of July 14-20, 2024.

Growing degree day (GDD) dynamic maps for the Canadian prairies for Base 5 ºC and Base 10 ºC (April 1-July 22, 2024) can be viewed by clicking the hyperlinks. Over the past 7 days (to July 23, 2024), the lowest temperatures recorded across the Canadian prairies ranged from 2 to 14 °C while the highest temperatures observed ranged from 5 to 35 °C. By now, note the mapped number of Days Above 25 ºC then compare to the Days Above 30 ºC (as of July 23, 2024). In terms of precipitation across the Canadian prairies, review the growing season accumulated precipitation (April 1-July 23, 2024), the growing season percent of average precipitation (April 1-July 23, 2024), and the past 7 days (as of July 23, 2024). Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

Growers can bookmark the AAFC Maps of Current Agroclimate Conditions for the growing season. Historical weather data can be accessed at the AAFC Drought Watch Historical website, Environment and Climate Change Canada’s Historical Data website, or your provincial weather network. The AAFC Canadian Drought Monitor also provides geospatial maps updated monthly.

Aphids in field crops

Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Access the Provincial Insect Pest Report for Wk12 to remain alert to areas and crops suffering from aphid pest pressure.

Figure 1. Pea aphid adults (each 3-4 mm long) and nymph. Photo: M. Dolinski.

Biological and monitoring information (including tips for scouting and economic thresholds) related to aphids in field crops is posted by:
• Manitoba Agriculture (aphids on cereals, aphids on flax, soybean aphid, aphids on peas)
• Saskatchewan Pulse Growers (aphids in pulse crops or access the PDF copy)
• Saskatchewan Flax Development Commission
• Manitoba Pulse and Soybean Growers (soybean aphids: identification, scouting and management or access the PDF copy)
• The Canola Council of Canada’s “Canola Encyclopedia” section on aphids
• or check your provincial commodity group’s insect pest webpages for more detailed information.

Alternatively, several aphid pest species are described in the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) and is accessible as a free downloadable PDF in either English or French on our Field Guides page. PDF copies of the individual pages have been linked below to access quickly:
• Corn leaf aphid or Rhopalosiphum maidis (Fitch)
• English grain aphid or Sitobion (Macrosiphum) avenae (Fabricius)
• Oat-birdcherry aphid or Rhopalosiphum padi (Linnaeus)
• Pea aphid or Acyrthosiphon pisum (Harris)
• Potato aphid or Macrosiphum euphorbiae (Thomas)
• Soybean aphid or Aphis glycines (Matsumura)
• Turnip aphid or Lipaphis erysimi (Kaltenbach)
• Sugar beet root aphid or Pemphigus betae Doane
• Russian wheat aphid or Diuraphis noxia (Mordvilko)

Over the years, both the Weekly Updates and Insect of the Week have included aphid-related information but also important natural enemy details to support in-field scouting. Review the list below so pest and beneficial insects can be distinguished readily when scouting fields:
• Aphidius wasp (Insect of the Week; 2015 Wk15)
• Aphids in canola (Insect of the Week; 2016 Wk13)
• Aphids in cereals (Insect of the Week; 2017 Wk09)
• Cereal aphid manager APP (Weekly Update; 2021 Wk07) that presently is available only for iOS
• Ladybird larva vs. lacewing larva (Insect of the Week; 2019 Wk18)
• Ladybird beetles and mummies (Weekly Update; 2020 Wk15)
• Lygus bug nymphs vs. aphids (Insect of the Week; 2019 Wk16)
• Hoverflies vs. bees vs. yellow jacket wasps (Insect of the Week; 2019 Wk19)
• Pea aphids: a persistent problem for legume growers (Insect of the Week; 2021 Wk12)
• Soybean aphids and aphid annihilating allies (Insect of the Week; 2022 Wk07)
• Syrphid flies (Insect of the Week; 2015 Wk16)

Canola Flower Midge Scouting

Scouting for canola flower midge tends to be easiest as the flowering stage of canola ends and pod development begins. Female canola flower midge lay eggs on developing canola buds and larvae develop inside the buds, resulting in galled flowers that do not open or produce pods.

Although canola flower midge does not appear to occur at densities that cause economic damage, scouting for canola flower midge will help to monitor population growth at the local scale to avoid surprises in the future. The monitoring protocol used during our survey from 2017-2019 is now available online so that everyone can scout for canola flower midge.

Check out the Canola Flower Midge Scouting post from Week 10 in 2023 for pictures of damage caused by this insect and to see a map of canola flower midge distribution.

Compare canola flower midge damage to the closely related Swede midge which was featured as Wk12’s Insect of the Week.

Access the Provincial Insect Pest Report for Wk12 for updates for this economic insect pest.

Bertha armyworm

Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies. Access the Provincial Insect Pest Report for Wk12 for updates for this economic insect pest.

Remember: in-field scouting is required to apply the economic threshold to manage both this pest and its natural enemies. Use the images below (Fig. 1) to help identify moths from the by-catch that will be retained in the green phermone-baited unitraps.

Figure 1. Stages of bertha armyworm from egg (A), larva (B), pupa (C), to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada).

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting or review the 2024 Insect of the Week featuring bertha armyworm. Also scan over the 2019 Insect of the Week featuring bertha armyworm and its doppelganger, the clover cutworm! 

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also, refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.

Diamondback moth

Scouting and pest management for diamondback moth depends on in-field counts of larvae per metre2! This means plants need to be pulled and tapped off to assess the number of larvae! Use Figure 1 below to help identify the different stages of the diamondback moth.

Figure 1. The life stages of the diamondback moth (Plutella xylostella), which can have multiple generations per year. Photos: AAFC-Saskatoon-J. Williams.

The economic threshold for immature and flowering canola is 100-150 larvae per metre2.

Access the Provincial Insect Pest Report for Wk12 for updates for this economic insect pest.

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture, Saskatchewan Ministry of Agriculture, Alberta Agriculture and Irrigation, and the Prairie Pest Monitoring Network.  Also, refer to the diamondback moth pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our Field Guides page.

Lygus bug monitoring

On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.

Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps. In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.

Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind: Begin monitoring canola when it bolts and continues until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.

How to tell them apart: The 2019 Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids!  Both posts include tips to discern the difference between when doing in-field scouting!

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.

Grasshopper

Grasshopper Scouting Tips:
● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species to aid in-field scouting from egg hatch and onwards.
● It is best to scout on warm days when grasshopper nymphs are more active and easier to observe.
● Carefully check roadside ditches and along field edges but also check the edge of the crop and into the actual field.
● Younger or earlier instar nymphs are easier to manage – visit sites every few days to stay on top of local field conditions.
● A sweep-net can ‘detect’ grasshopper nymphs, however, economic thresholds for grasshoppers are based on the number of grasshoppers per square-metre counts.
● Access the PPMN’s Grasshopper Monitoring Protocol as a guide to help implement in-field monitoring.
● Review grasshopper lifecycle, damage and scouting and economic thresholds to support sound management decisions enabling the preservation of beneficial arthropods and mitigation of economic losses.

Important – A preliminary summary of available thresholds for grasshoppers has been kindly shared by Dr. J. Tansey (Saskatchewan Agriculture) in Table 1. When scouting, compare in-field counts to the available threshold value for the appropriate host crop AND for field or ditch situations. Available thresholds (nominal and economic) help support producers while protecting beneficials (i.e., predators, parasitoids, and pathogens) that regulate natural populations of grasshoppers.

Access the Provincial Insect Pest Report for Wk12 for updates for this economic insect pest.

Biological and monitoring information (including tips for scouting and economic thresholds) related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Ministry of Agriculture, Alberta Agriculture and Irrigation, the BC Ministry of Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our Field Guides page. Review the historical grasshopper maps based on late-summer in-field counts of adults performed across the Canadian prairies.

Provincial insect pest report links

Prairie-wide provincial entomologists provide insect pest updates throughout the growing season. Follow the hyperlinks to readily access their information as the growing season progresses:

MANITOBA’S Crop Pest Updates for 2024 are available. Access the online July 25, 2024 report (or PDF copy). Bookmark the insect pest homepage to access fact sheets and more! Highlights pulled from the latest report include:
• Aphids – Dr. J. Gavloski reported that, “Pea aphids in peas” remained a concern that resulted in “some control in the Southwest, Central and Interlake regions”. Additionally, “aphids in cereal crops are becoming more noticeable in some areas” but there also were “reports of aphid mummies (parasitized aphids), lacewings and lots of lady beetles in some fields of wheat.”
• True armyworm – “True armyworms were still noted in forage grasses in the Central and Interlake regions. There were no reports of control of true armyworms over the past week, and levels of larvae may be declining as they turn to pupae. Review the cumulative pheromone trap counts in the July 24, 2024 report. Also find reports of natural enemies of armyworm in this report.
• Grasshoppers– Reports that, “grasshoppers are more noticeable in crops in some areas, while in other areas grasshopper activity is mainly limited to field edges or is of less concern. There was a report of a number of dead grasshoppers clinging to the top of wheat heads (a sign of a fungal pathogen) in the Southwest region.”
• Canola flower midge – “Unopened buds, a result of canola flower midge, is noticeable in some canola fields in the Northwest region.”
• European corn borer – Review the report for tips to scout for egg masses in corn, hemp, quinoa, potatoes and other host crops. Access both the updated fact sheet and request to report by downloading and using the free Survey123 App.
• Corn rootworm – Review the report for tips to scout for both the northern and western corn rootworm.
• Bertha armyworm pheromone trap monitoring – Reports moths in “79 of 82 traps” although “counts have been low so far”. So far, the highest cumulative count reported is “290 from a trap near Killarney in the Southwest region”. Access the PDF copy of the July 25 report.
• Diamondback moth pheromone trap monitoring – Trapping is complete for 2024 (as of Wk 09; access the PDF copy of the July 4 report).

SASKATCHEWAN’S Crop Production News is back for the 2024 growing season! Access the online Issue #5 report which includes sections covering pea aphids and cereal leaf beetle. Bookmark their insect pest homepage to access important information! Also access the Crops Blog Posts that released a grasshopper activity update (June 2024), announced registration for the Crop Diagnostic School 2024 but also posts help for scouting fields for wireworms (May 2024), grasshopper identification: pest or not (Apr 2024), a summary of wheat midge populations and management (Mar 2024), and a description of pea leaf weevil populations (Feb 2024).
• A brief summary of notable insect pests relayed from Dr. J. Tansey is that insecticide control has been needed to protect lentils from pea aphids. And similarly with other aphids – this past week, an increased number of reports and calls were received related to cereal aphids.

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. Remember, AAI’s Agri-News occasionally includes insect-related information, e.g., assessing and a description of missing pods on canola (July 22, 2024), scout for wheat midge (July 15, 2024), the right canola crop stage to spray for lygus bugs (July 8, 2024), soil moisture, wheat midge and other insect pests (June 24, 2024), scout for grasshoppers and other insect pests (June 17, 2024); how to manage stem feeding from flea beetles, keep canola bins malathion-free, scout for grasshoppers and other pests (June 10, 2024); scout for insect pests (June 3, 2024); scout for grasshoppers (May 27, 2024); flea beetle control (May 6, 2024); cereal insect pests, latest on insects in canola, and post-emergence wireworm scouting (May 13, 2024).
• Wheat midge monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. So far, cumulative trap counts from 37 trap locations are reporting; 10 sites in central Alberta are “high” and in the Peace River region 22 sites are reporting “high”, 2 sites are “medium”, and 2 sites are “low” (as of July 25, 2024).
• Cabbage seedpod weevil monitoring – Sweep-net count data can be reported here then the data populates the Live Map. So far, a total of 16 sites in southern Alberta are reporting; there are 14 “low risk” plus 2 “high risk” reports as of July 18, 2024).
• Bertha armyworm pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. Cumulative trap counts from 266 trap locations are all reporting “low risk” across the province while 1 trap location near Fairview, plus 3 trap locations in southern Alberta (2 in Vulcan County plus 1 near Lethbridge) are reporting “medium risk” as of July 25, 2024).
• Diamondback moth pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map. Cumulative trap counts have been recorded from 32 reporting sites and 28 remain in the “no risk” category as of July 4, 2024). Four trap locations have caught > 25 adult diamondback moths; sites fall within the County of Grande Prairie (as of June 8, 2024), County of Warner (as of June 15, 2024), Vulcan County (as of June 15, 2024), and County of Barrhead (as of June 15, 2024).
• Cutworm live monitoring map – Cumulative counts arising from weekly data are available so refer to the Live Map. 10 surveyed sites have reported from across the province, nine falling within southern Alberta and one report from the County of Grande Prairie.

Crop report links

Access the latest provincial crop reports produced by:
• Manitoba Agriculture (subscribe to receive OR access a PDF copy of the July 23, 2024 report).
• Saskatchewan Agriculture (or access a PDF copy of the July 16-22, 2024 report).
• Alberta Agriculture and Irrigation (or access a PDF copy of the July 16, 2024 report).
• The high temperatures and lack of precipitation across large areas of the Canadian prairies for ~10 days starting on July 9, 2024, will be reflected in the above reports.

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 22, 2024 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 23, 2024 edition).

Previous posts

As the growing season progresses, the Weekly Update topics move on and off the priority list for in-field scouting. It remains useful to keep the list at hand to support season-long monitoring. Click to review these earlier 2024 Posts (organized alphabetically):
• 2023 Risk maps
• Alfalfa weevil (Wk 09)
• Cabbage seedpod weevil (Wk 10)
• Cereal leaf beetle (Wk 10)
• Cicada – Rare co-emergence of broods (Wk07)
• Crop production guide links (Wk 03)
• European skipper (Wk 11)
• Cutworms (Wk 05)
• Field heroes (Wk 05)
• Flea beetles (Wk 04)
• Invasive insects (Wk 06)
• Monarch migration (Wk 10)
• Pea leaf weevil (Wk 05)
• Prairie Crop Disease Monitoring Network (Wk 08)
• Prairie Weed Monitoring Network (Wk 06)
• Scouting charts – canola and flax (Wk 03 of 2022)
• Tick tips (Wk 04)
• True armyworm (Wk 09)
• West Nile virus (Wk 09)
• Wind trajectory summaries unavailable (Wk 01)
• Wheat midge (Wk 11)

2023 Week 12 (Released July 27, 2023)

It sounds like harvest has started in some parts of the prairies in the past week, but crop development and insect pest issues are variable across the prairie region. Insect scouting season continues! Development of many pest insects (and of their host crops) is ahead of schedule this year, thanks to warmer than average weather during this growing season.

Adult grasshoppers are becoming more and more common across the prairies. The stage of grasshopper development and grasshopper population densities can vary between fields, thus scouting individual fields is important to best estimate crop risk. Now that adult grasshoppers are active, egg laying has begun.

Diamondback moth, if present, are into the fourth non-migrant generation in some parts of the prairies now. Keep in mind that diamondback moth develop quickly in warm weather which could lead to rapidly increasing populations over the summer. Scout canola fields for diamondback moth larvae and use the links in the Provincial Insect Updates post to learn about diamondback moth risk in your region. Parasitoids of diamondback moth are highlighted in the Week 12 Insect of the Week!

Watch out for Invasive and Migrating Insects! If you suspect that you have found any of the insects on the Prairie Region Poster, please let us know using the form linked to the QR code on the poster. Note: many of us entomologists on the prairies are members of the Insect Surveillance Community of Practice!

Remember: 1) there are many resources available to help with planning for late-season insecticide applications to ensure Pre-Harvest Interval requirements are met, and 2) insect Monitoring Protocols containing information about in-field scouting as well as information about insect pest biology and identification are available from the Prairie Pest Monitoring Network.

To receive Weekly Updates automatically, please subscribe to the website!

Questions or problems accessing the contents of this Weekly Update? Please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca) to get connected to our information. Past Weekly Updates, full of information and helpful links, can be accessed on our Weekly Update page.

Weather Synopsis

During the week of July 17-23, 2023, the prairie average daily temperature was 1°C warmer than the climate normal average daily temperature for the same period. The coolest temperatures were observed across eastern Saskatchewan, western Manitoba, and the Peace River region. The warmest weekly average temperatures occurred across southern Alberta and southwestern Saskatchewan (Fig. 1). 

Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of July 17-23, 2023. 

Average prairie daily temperatures over the past 30 days (June 24 – July 23, 2023) have been 1°C above normal. Many locations in the Peace River region have reported 30-day average temperatures that were 4°C warmer than average, so it was no surprise that the warmest temperatures in the last 30 days were reported across most of the southern prairies and the Peace River region (Fig. 2).

Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 24 to July 23, 2023. 

Growing season (April 1 – July 23, 2023) temperatures continue to be warmer than normal by 1.7°C. For the growing season so far, the warmest temperatures have occurred across the southern regions of all three prairie provinces (Fig. 3).

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 23, 2023. 

Precipitation for the week of July 17-23, 2023 was minimal across most of the prairies; only the Parkland region had rainfall amounts that were greater than 20mm (Fig. 4).

Figure 4. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 17-23, 2023. 

In the last 30 days (June 24 to July 23), the average cumulative prairie precipitation was 35 mm, which is only 62% of the precipitation we would normally receive in the same period of the growing season. Cumulative rainfall in the past 30 days was greatest in the Edmonton  and Winnipeg regions and the lowest rainfall totals continue to be those recorded across most of Saskatchewan and southern Alberta (Fig. 5). 

Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 24 – July 23, 2023. 

Since April 1, conditions have generally been dry across the prairies, with some notable exceptions. Most of the prairie region has now received approximately 90% of total rainfall we would expect to receive based on long-term climate normals. Below normal precipitation has occurred across most of Saskatchewan and southern Alberta (Fig. 6). During the current growing season, the warmest and driest area of the prairies continues to be southern Alberta and the western half of Saskatchewan. 

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 23, 2023. 

Predicted Grasshopper Development

Grasshopper risk may be significant for large areas of Alberta, Saskatchewan, and southern Manitoba. In 2023, grasshoppers developed to the adult stage earlier than normal (by nearly 2 weeks!) and high densities of grasshoppers have been observed in many regions. Grasshoppers are exacerbating crop yield losses in drought-affected areas.

Model simulations were used to estimate the developmental stage of grasshoppers as of July 23, 2023. Simulations indicate that 54% of the prairie population should be in the adult stage (51% last week). Grasshopper development continues to be well ahead of average in 2023. For example, in an average year, based on long-term average weather, we would expect only 10% of the population to be in the adult stage at the end of July.

Following early development to the adult stage, grasshopper reproduction is now expected to be underway. Our grasshopper model indicates that oviposition has begun across most of the prairies (Fig. 1).

Figure 1. Proportion (%) of the migratory grasshopper (Melanoplus sanguinipes) population expected to be in the egg stage across the Canadian prairies as of July 23, 2023. 

Geospatial maps are a tool to help time in-field scouting on a regional scale but grasshopper development and population densities can vary from place to place. Scouting is required to accurately assess the stage of grasshopper development and to estimate grasshopper densities.

Information about grasshoppers and grasshopper monitoring is available from the Prairie Pest Monitoring Network, in the Field Crop and Forage Pests guide, Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, and Manitoba Agriculture. 

Predicted Diamondback Moth Development

A fourth generation of non-migrant adult diamondback moths could be flying right now in southern Manitoba and in southeastern Alberta (Fig. 1). This prediction is based on model simulations to July 23, 2023 using early May arrival dates for diamondback moth adults that migrated into western Canada in the spring.

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred (or be occurring) across the Canadian prairies as of July 23, 2023.  

Compared to past years, warm weather in 2023 has sped up the development of diamondback moth. Using long-term average weather data (also known as climate normal data), model simulations to July 23 indicate that a second or third non-migrant generation of diamondback moth should be occurring right now (Fig. 2). In 2023, we could already be seeing a fourth generation!

Figure 2. The number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 23, based on climate normal data. 

Some areas of the prairies might be at risk of damage from diamondback moth this summer. Pheromone traps with cumulative counts greater than 25 male moths were located around Cadillac, Rosetown, Makwa, Eatonia, and Swift Current in Saskatchewan and in all regions of Manitoba (see the July 5 and July 19 editions of the Crop Pest Report). In Alberta, Shelley Barkley is finding diamondback moth larvae in canola samples from Yellowhead county, Parkland county, the Leduc area, and the Bonnyville area.  

Because diamondback moth can have multiple generations in a single growing season and because the generation time is shorter when temperatures are warm, their populations can build up quickly. Keep scouting for diamondback moth to avoid unpleasant surprises at the end of this summer.

To scout for diamondback moth, estimate the number of diamondback moth larvae per m2 at several locations in a field. The economic threshold for diamondback moth is NOT based on pheromone traps or sweep net samples, but on the density of larvae per plant. For immature and flowering canola, the economic threshold is 100-150 larvae/m2. In podded canola, the economic threshold is 200-300 larvae/m2. See the Field Crop and Forage Pests guide and monitoring protocol for more information about scouting for diamondback moth.

Watch Out for Invasive Insects

Invasive insects are a threat to agriculture and forestry in Canada. The Insect Surveillance Community of Practice is asking anyone monitoring, photographing, or observing insects to be on the lookout for invasive insects across Canada. They have developed posters for four regions of Canada, including the Prairies, with pictures and information about potentially invasive insects of concern to each region.

Early detection is critical for slowing the spread of invasive insects. Please view the poster for your region using the links below to learn more about insects to watch out for. Use the QR code on the poster to report your detections/observations.

A sample of the first page of the Prairie Region poster of invasive and migratory insects to watch for.

Prairie Region (French version here)

British Columbia (French version here)

Ontario & Quebec (French version here)

Atlantic Canada (French version here)

This initiative is a collaborative project developed by the Insect Surveillance Community of Practice of the Canadian Plant Health Council, a multi-partner body that coordinates action for the protection of plant health in Canada. 

Pre-harvest Intervals (PHI)

As harvest is nearing (if not already begun), it is necessary to consider PHI before applying pesticides for late-season pests. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop and reflects the time required for pesticides to break down after being applied. PHI values are both crop- and pesticide-specific.  Adhering to the PHI is important for a number of health-related reasons and to ensure that crops being sold for export meet pesticide residue limit requirements.

Helpful resources include:
• The Keep It Clean website, with information about PHI and Maximum Residue Limits (MRL)
• The Pest Management Regulatory Agency fact sheet, “Understanding Preharvest Intervals for Pesticides”, with a free copy available to download
• Keep It Clean’s “Pre-Harvest Interval Calculator” that will help to accurately estimate PHI for a variety of crops
• The Pre-Harvest Glyphosate Stage Guide
• The provincial crop protection guides include the PHI for every pesticide by crop combination. The 2023 Crop Protection Guides are available as FREE downloadable PDFs for Alberta, Saskatchewan, and Manitoba.

Provincial Insect Updates

Visit the Alberta Insect Pest Monitoring Network and Crop Insects pages for information about insects and monitoring in Alberta, including links for live maps from the 2023 monitoring season for diamondback moth, bertha armyworm, cutworms, and cabbage seedpod weevil.

Saskatchewan Crop Production News issues are now online! Use this link to read Issue #3. Issue #3 for 2023 includes information about grasshoppers and Lauxanid flies, as well as about plant diseases and some notes about plant development across Saskatchewan. There are links on the Crop Production News page so that interested readers can subscribe to the newsletter or read issues from past years.

Weekly Manitoba Crop Pest Updates for 2023 are available online with timely updates about insect pests, weeds, and plant pathogens. Watch their website for new Crop Pest Updates (usually published on Wednesdays this year).

PARASITOIDS OF DIAMONDBACK MOTH

This week, our insects of the week are the natural enemies of diamondback moth found on the Prairies! Four important parasitoids attack this pest: Diadegma insulare, Diadromus subtilicornis, Microplitis plutellae, and Trichogramma praetiosum.

A pupa of the parasitoid Diadegma insulare inside its cocoon. Picture credit: Andrea Brauner, AAFC.

Some of these species (like Diadegma insulare) follow diamondback moth on its yearly migration from the southern United States and some (like Micropletis plutellae) overwinter in Canada and can help with early-season control. These small, dark colored wasps occasionally completely control diamondback moth outbreaks in Canada! 

Parasitoids of diamondback moth. On the left: Diadegma insulare. On the right: Microplitis plutellae. Both pictures taken by Amanda Jorgensen, AAFC-Beaverlodge Research Farm.

The four parasitoid species attack during different stages of the diamondback moth lifecycle. Diadegma and Micropletis parasitoids attack larval diamondback moth. Trichogramma and Diadromus species attack the prepupal and pupal stages.

A female Diadromus parasitoid preparing to parasitize a diamondback moth pupa. Picture credit: Andrea Brauner, AAFC.

There is a long list of other wasp species that have been found to parasitize diamondback moth larvae to a lesser extent. Hoverfly larvae, yellowjacket wasps, lacewings, plant bugs, pirate bugs, beetles, spiders and birds also prey on diamondback moth larvae. 

Biological and monitoring information related to diamondback moths in field crops can be found on our Monitoring page as well as on provincial Agriculture Ministry pages (Manitoba, Saskatchewan and Alberta). For more information, visit the diamondback moth page in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien). You can find more information about some of the parasitoids of diamondback moth on the field heroes website or learn about Braconid wasp life cycles here. 

Released July 29, 2022

This week includes…..

• Weather synopsis
• Predicted grasshopper development
• Predicted diamondback development
• Predicted wheat midge development
• Aphids in field crops
• Lygus bug monitoring
• Cabbage seedpod weevil monitoring
• Pea leaf weevil monitoring
• West Nile virus risk
• Extension survey for Albertans
• Pre-harvest intervals (PHI)
• Provincial insect pest report links
• Crop report links
• Previous posts
….and Monday’s Insect of the Week for Week 12 – it’s Western bean cutworm (Striacosta albicosta)!

Wishing everyone good SCOUTING weather!

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Questions or problems accessing the contents of this Weekly Update?  Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.

Weather synopsis

TEMPERATURE: Though temperatures over the past 30 days have been warmer than normal, the 2022 growing season across the prairies has been quite similar to that of a ‘normal’ or long-term average season. This past week (July 18-24, 2022), the average daily temperature on the prairies was 2 °C cooler than the average daily temperature of the previous week and 1 °C warmer than the long-term normal temperature. The coolest temperatures were observed across central and northern Alberta (Fig. 1).

Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 18-24, 2022.

The prairie-wide average 30-day temperature (June 25 – July 24, 2022) was 0.5 °C warmer than the long-term average value. Average temperatures have been warmest across the southern prairies (Fig. 2).

Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 25-July 24, 2022.

The average growing season (April 1-July 24, 2022) temperature for the prairies has been 0.2 °C cooler than the climate normal values. The growing season has been warmest across the southern prairies (Fig. 3).

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 24, 2022.

PRECIPITATION: Weekly rainfall accumulation for July 18 to 24 varied across the prairies. Very little precipitation has fallen across the northern prairies (Fig. 4). Observed rainfall amounts across central and northern Alberta were generally less than 5 mm. 30-day (June 25 – July 24, 2022) rainfall amounts have been well below average for the northern prairies and near normal across the southern prairies (Fig. 5).

Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 18-24, 2022.
Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 25-July 24, 2022).

Growing season rainfall for April 1 – July 24, 2022, continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been much lower for the central and western regions of Saskatchewan and Alberta (Fig. 6).

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 24, 2022.

Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-July 25, 2022) can be viewed by clicking the hyperlinks. Over the past 7 days (July 12-18, 2022), the lowest temperatures recorded across the Canadian prairies ranged from < 0 to >12 °C while the highest temperatures observed ranged from <23 to >32 °C. Review the days at or above 25 °C across the prairies and also the days at or above 30 °C. Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Current Conditions Maps for the growing season. Historical weather data can be accessed at the AAFC Drought Watch Historical website, Environment Canada’s Historical Data website, or your provincial weather network. The AAFC Canadian Drought Monitor also provides geospatial maps updated monthly.

Predicted grasshopper development

The grasshopper (Acrididae: Melanoplus sanguinipes) model predicts development using biological parameters known for the pest species and environmental data observed across the Canadian prairies on a daily basis. Model outputs provided below as geospatial maps are a tool to help time in-field scouting on a regional scale yet local development can vary and is only accurately assessed through in-field scouting.

Some areas of the Canadian prairies are presently experiencing high densities of economically important species. Review lifecycle and damage information for this pest to support in-field scouting.

Model simulations were used to estimate grasshopper development as of July 24, 2022. As a result of above-normal temperatures, grasshopper development has rapidly progressed over the past few weeks. Last week, adults were just beginning to appear. Based on estimates of average development, populations should consist of 4th (25%) and 5th (34%) instar nymphs and adults (19%) across the southern regions of all three prairie provinces (Fig. 1). Adults should now be occurring across the southern regions of all three prairie provinces (Fig. 2). Potential risk continues to be greatest across the central and southern regions of Saskatchewan.

Figure 1. Predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 24, 2022.
Figure 2. Long-term average predicted migratory grasshopper (Melanoplus sanguinipes) development, presented as the percent adults, across the Canadian prairies as of July 17, 2022.

Grasshopper Scouting Tips:
● Review grasshopper diversity and photos of nymphs, adults, and non-grasshopper species to aid in-field scouting from egg hatch and onwards.
● Access the PPMN’s Grasshopper Monitoring Protocol as a guide to help implement in-field monitoring.
● Review grasshopper lifecycle, damage and scouting and economic thresholds to support sound management decisions enabling the preservation of beneficial arthropods and mitigation of economic losses.

Biological and monitoring information (including tips for scouting and economic thresholds) related to grasshoppers in field crops is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. Review the historical grasshopper maps based on late-summer in-field counts of adults performed across the prairies.

Predicted diamondback moth development

Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.

Model simulations to July 24, 2022, indicate that the third generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the southern prairies (Fig. 1). DBM development is predicted to be marginally greater than long-term average values (Fig. 2).

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 24, 2022.
Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 24, based on climate normal data.

Spring Pheromone Trap Monitoring of Adult Males: Across the Canadian prairies, spring monitoring is initiated to acquire weekly counts of adult moths attracted to pheromone-baited delta traps deployed in fields. Weekly trap interceptions are observed to generate cumulative counts. Summaries or maps of cumulative DBM data are available for Manitoba, Saskatchewan and Alberta. These cumulative count estimates are broadly categorized to help producers prioritize and time in-field scouting for larvae.

In-Field Monitoring: Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 2) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.

Figure 2. Diamondback larva measuring ~8mm long.
Note brown head capsule and forked appearance of prolegs on posterior.

The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant).  Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).

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Figure 3. Diamondback moth pupa within silken cocoon.
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Figure 4. Diamondback moth.

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the diamondback moth pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.

Diamondback moth was the Insect of the Week for Wk10 in 2021!

Predicted wheat midge development

The following maps represent predicted regional estimates of wheat midge development. Remember – field level populations are assessed only through in-field scouting.

As of July 24, 2022, where wheat midge is present, model simulations predict that Albertan populations should be primarily in the egg stage, while populations across Manitoba and eastern Saskatchewan should consist of larvae developing in wheat heads (Fig. 1).

Figure 1. Wheat midge larvae (AAFC)

Regional differences in wheat midge development can be attributed to rainfall differences that occurred in May and June. Optimal rainfall in May and June across Saskatchewan and Manitoba has resulted in faster rates of wheat midge development rates than in Alberta. As a result, some adult wheat midge may still be active in Alberta (Fig. 2), while adult populations should have peaked and should be declining across Saskatchewan and Manitoba. Populations in the Peace River region are predicted to be primarily in the egg stage (Fig. 3). Across Manitoba and Saskatchewan, populations are predicted to be transitioning from the egg stage to the larval stage (Fig. 4). Wheat midge developmental rates near Regina, Saskatchewan are predicted to be greater than for Grande Prairie, Alberta.

Figure 2. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the adult stage, across western Canada, as of July 24, 2022.
Figure. 3. Percent of wheat midge population (Sitodiplosis mosellana) that is in the egg stage across western Canada, as of July 24, 2022.
Figure 4. Percent of wheat midge population (Sitodiplosis mosellana) that is in the larval stage (in wheat heads), across western Canada, as of July 24, 2022.

Model simulations indicate that egg development is complete and populations are primarily in the larval stage (>90%) for populations near Regina (Fig. 5) while Grande Prairie populations are predicted be in both egg (31%) and larval stages (61%) (Fig. 6). Potential risk continues to be greatest across eastern Saskatchewan and Manitoba.

Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of July 24, 2022.
Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta, as of July 24, 2022.

In-Field Monitoring: The window for scouting and application of the economic threshold for wheat midge (i.e., during the synchrony between wheat anthesis and midge flight period) has now drawn to a close for 2022. 

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  Wheat midge was featured as the Insect of the Week in 2021 (for Wk07).

Additional information can be accessed by reviewing the Wheat midge pages extracted from the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page.

Aphids in field crops

Aphid populations can quickly increase at this point in the season and particularly when growing conditions are warm and dry. Over the years, both the Weekly Updates and Insect of the Week included aphid-related information so here’s a list of these items to access when scouting fields:

• Aphidius wasp (Insect of the Week; 2015 Wk15)
• Aphids in canola (Insect of the Week; 2016 Wk13)
• Aphids in cereals (Insect of the Week; 2017 Wk09)
• Cereal aphid manager APP (Weekly Update; 2021 Wk07)
• Ladybird larva vs. lacewing larva (Insect of the Week; 2019 Wk18)
• Ladybird beetles and mummies (Weekly Update; 2020 Wk15)
• Lygus bug nymphs vs. aphids (Insect of the Week; 2019 Wk16)
• Hoverflies vs. bees vs. yellow jacket wasps (Insect of the Week; 2019 Wk19)
• Syrphid flies (Insect of the Week; 2015 Wk16)

Lygus bug monitoring

On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.

Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect that focuses feeding activities on developing buds, pods and seeds. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Recent research in Alberta has resulted in a revision to the thresholds recommended for the management of Lygus in canola. Under ideal growing conditions (i.e., ample moisture) a threshold of 20-30 lygus per 10 sweeps is recommended. Under dry conditions, a lower threshold may be used, however, because drought limits yield potential in canola, growers should be cautious if considering the use of foliar-applied insecticide at lygus densities below the established threshold of 20-30 per 10 sweeps. In drought-affected fields that still support near-average yield potential, a lower threshold of ~20 lygus per 10 sweeps may be appropriate for stressed canola. Even if the current value of canola remains high (e.g., >$19.00 per bu), control at densities of <10 lygus per 10 sweeps is not likely to be economical. Research indicates that lygus numbers below 10 per 10 sweeps (one per sweep) can on occasion increase yield in good growing conditions – likely through plant compensation for a small amount of feeding stress.

Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs.

How to tell them apart: The 2019 Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids!  Both posts include tips to discern the difference between when doing in-field scouting!

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes Lygus bugs. The Flax Council of Canada includes Lygus bugs in their Insect Pest downloadable PDF chapter plus the Saskatchewan Pulse Growers summarize Lygus bugs in faba beans.

Cabbage seedpod weevil monitoring

There is one generation of cabbage seedpod weevil (CSPW; Ceutorhynchus obstrictus) per year. The overwintered adult is an ash-grey weevil measuring 3-4mm long (e.g., lower left photo).  Mating and oviposition are quickly followed by eggs hatching within developing canola pods (e.g., lower right photo). The highly concealed larvae feed within the pod, consuming the developing seeds.

Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss.  Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo).  Eggs are oval and an opaque white, each measuring ~1mm long.  Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.

There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo).  The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds.  A single larva consumes about 5 canola seeds.  The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell.  Approximately 10 days later, the new adult emerges to feed on maturing canola pods.  Later in the season, these new adults migrate to overwintering sites beyond the field.

Monitoring:

  • Begin sampling when the crop first enters the bud stage and continue through the flowering. 
  • Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.  
  • Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.  
  • Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.  
  • An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). 
  • Consider making insecticide applications late in the day to reduce the impact on pollinators.  Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.  
  • High numbers of adults in the fall may indicate the potential for economic infestations the following spring.

Albertan growers can report and check the live map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 2022Jul28).

CSPW was the Insect of the Week for Wk08 in 2021!

Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.  Also refer to the cabbage seedpod weevil pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) accessible as a free downloadable PDF in either English or French on our new Field Guides page. The Canola Council of Canada’s “Canola Encyclopedia” also summarizes CSPW.

Pea leaf weevil monitoring

The pea leaf weevil is a slender greyish-brown insect measuring approximately 5 mm in length (Fig. 1, Left image). Pea leaf weevil resembles the sweet clover weevil (Sitona cylindricollis) but the former is distinguished by three light-coloured stripes extending length-wise down thorax and sometimes the abdomen.  All species of Sitona, including the pea leaf weevil, have a short snout.  

Figure 1.  Comparison images and descriptions of four Sitona species adults including pea leaf weevil (AAFC-Otani).

Adults will feed upon the leaf margins and growing points of legume seedlings (alfalfa, clover, dry beans, faba beans, peas) and produce a characteristic, scalloped (notched) edge (Fig. 2).  Females lay their eggs in the soil either near or on developing pea or faba bean plants from May to June.

Figure 2. Examples of adult pea leaf weevil damage on field pea seedlings, (A) seedling with notches on all nodes, (B) stereotypical crescent shaped notches on the leaf margin, (C) clam or terminal leaf of the pea seedling with arrows indicating the feeding notches.
All photos courtesy of Dr. L. Dosdall.

Larvae develop under the soil and are “C” shaped and milky-white with a dark-brown head capsule ranging in length from 3.5-5.5 mm (Figure 3).  Larvae develop through five instar stages.  After hatching, larvae seek and enter the roots of a pea plant.  Larvae will enter and consume the contents of the nodules of the legume host plant. It is the nodules that are responsible for nitrogen-fixation which affect yield plus the plant’s ability to input nitrogen into the soil. Consumption of or damage to the nodules (Figure 4) results in partial or complete inhibition of nitrogen fixation by the plant and results in poor plant growth and low seed yields.

Figure 3. Larva of pea leaf weevil in soil (Photo: L. Dosdall).
Figure 4. Damaged pea nodules (Photo: L. Dosdall).

Biological and monitoring information related to pea leaf weevil in field crops is posted by the province of Alberta and in the PPMN monitoring protocol. Also access the Pea leaf weevil page from the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).

West nile virus risk

The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!

As of July 24, 2022, C. tarsalis development is now on the verge of the second generation of adults beginning to fly in areas highlighted yellow (i.e., 250-300 DD of base 14.3 °C) represented below in Figure 1. Outdoor enthusiasts falling within areas highlighted orange or yellow should begin to wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are now in a period of increased risk for WNV that typically peaks over the long weekend in August.

Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 24, 2022).

For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP is approximately 17 days in areas highlighted red and approximately 15 days in areas highlighted pink.

Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of July 24, 2022.

The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date November 18, 2021; retrieved July 28, 2022). The screenshot below (retrieved 28Jul2022) serves as a background reference of what was reported in 2021.

Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 28Jul2022).

Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.

Extension survey for Albertans

Prompted by recent discussions at Results Driven Agriculture Research (RDAR) meetings, a survey has been initiated as part of an M.Sc. research project in the Faculty of Science at the University of Alberta to assess the effectiveness and producer preferences for entomological extension in agriculture in Alberta. The project is funded by RDAR and the Alberta Pulse Growers.

Albertans can read the description of the survey or opt to complete the 20-minute online survey.

More information about this survey can be gained by contacting Ilan Domnich (domnich@ualberta.ca) or Dr. Maya Evenden (mevenden@ualberta.ca).

Pre-Harvest Intervals (PHI)

Start to consider pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop.  The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific.  Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.

Here are a few resources to help:
• Information about PHI and Maximum Residue Limits (MRL) is available on the Keep It Clean website.
• The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy.
• Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate:
◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas.
◦ How long to wait, if the crop’s already been sprayed.
◦ To find a pesticide to suit your timeline.
• Access the Pre-Harvest Glyphosate Stage Guide.
• And remember Provincial crop protection guides include the PHI for every pesticide x crop combination. The 2022 Crop Production Guides are available as a FREE downloadable PDF for Alberta, Saskatchewan, and Manitoba.

Provincial insect pest report links

Provincial entomologists provide insect pest updates throughout the growing season so link to their information:

MANITOBA’S Crop Pest Updates for 2022 are up and running! Access a PDF copy of the July 27, 2022 issue here. Bookmark their Crop Pest Update Index to readily access these reports and also bookmark their insect pest homepage to access fact sheets and more!
• Pea aphids, aphids in small grains, grasshoppers and armyworm larvae in MB were emphasized in the July 27 issue.
• Bertha armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 26, 2022) of cumulative weekly counts.
• Armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 12, 2022) of counts compiled from Manitoba, Eastern Canada and several northeast states of the United States.

SASKATCHEWAN’S Crop Production News for 2022 is up and running! Access the online Issue #5 (URL retrieved July 28, 2022) and find updates linking to information for Beneficial insects, and Managing grasshoppers. Bookmark their insect pest homepage to access important information! Crops Blog Posts are updated through the growing season and note this link for July’s Crop Diagnostic School.

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information. Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
• Wheat midge pheromone monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
• Cabbage seedpod weevil monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.
• Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available on this Live Map.

Crop report links

Click the provincial name below to link to online crop reports produced by:
• Manitoba Agriculture and Resource Development (or access a PDF copy of the July 26, 2022 report).
• Saskatchewan Agriculture (or access a PDF copy of the July 19-25, 2022 report).
• Alberta Agriculture, Forestry, and Rural Economic Development (or access a PDF copy of the July 12, 2022 report).

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 25, 2022 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 26, 2022 edition).

Previous posts

As the growing season progresses, the various Weekly Update topics move on and off the priority list for in-field scouting but they should be kept at hand to support season-long monitoring. Click to review these earlier 2022 Posts (organized alphabetically):
• 2021 Risk and forecast maps
• Alfalfa weevil – predicted development (Wk06)
• Bertha armyworm – predicted development (Wk07)
• Cereal leaf beetle – predicted development (Wk06)
• Crop protection guides (Wk02)
• Cutworms (Wk02)
• European corn borer – Canadian standardized assessment 2.0 (Wk02)
• Field heroes (Wk08)
• Field guides – New webpage to access (Wk02)
• Flea beetles (Wk01; IOTW)
• iNaturalist.ca (Wk02)
• Invasive insect species – Early detection (Wk02)
• Scouting charts – canola and flax (Wk03)
• Ticks and Lyme disease (Wk02)
• Wind trajectory reports released in 2

WESTERN BEAN CUTWORM – WILL THE RANGE EXPANSION REACH THE PRAIRIES?

Western bean cutworm (Striacosta albicosta) is a native North American insect that, at high levels, can be a pest of corn and dry beans. However, the way they feed is different than some of the other cutworms many may be familiar with. Western bean cutworm feeds on the reproductive parts of plants (corn tassel, silks, and kernels, or dry bean pods and seeds). This can result in yield loss, and spread ear mold. In Ontario, injury by western bean cutworm has been shown to increase mycotoxin production in grain corn.

Range Expansion: The historical geographic range of the western bean cutworm covered the western Great Plains states including Colorado, Nebraska, and Wyoming but, over the past two decades, its distribution has been more easterly rather than north to the prairies. A report from the 1950s of western bean cutworm in Alberta has instead been confirmed as a misidentification of another species. Currently, it has not been detected in the Canadian prairie provinces. Since 1999, the geographic range of the western bean cutworm has rapidly expanded eastward across the U.S. Corn Belt and eastern Canada. Western bean cutworm adults have been collected in 22 additional states and provinces since 1999, spreading from western Iowa to the east coast of the United States and Canada. It was first found in Canada in Ontario in 2008. Keep an eye open for this insect when scouting for crop pests in corn or dry beans this summer.

Figure 1. Detailed expansion of western bean cutworm distribution into the eastern Corn Belt between 2000 and 2017. From: Smith et al. 2019. Journal of Integrated Pest Management. Volume 10, Issue 1, pg. 1-19.

Appearance and monitoring tips:
Larvae:
• There are six stages (instars) of the larvae, and appearances vary.
• Older larvae are a light tan colour, with an orange head. The pronotum (the shield-like structure just behind the head) has two broad dark brown stripes.
• You may find young larvae on the silks of corn. Older larvae may be on the ears of corn, but you may have to peel back the husks to find them (Fig. 2).

Figure 2. Western bean cutworm feeding on corn. Photo: Jocelyn Smith, University of Guelph.


Adults:
• Each forewing has a white or tan band running along the edge or margin of the wing (Fig. 3). Inside this band are 2 distinctive markings: a brown circle and a brown kidney bean shape, both surrounded by a tan border.
Note – Other moths across the Canadian prairies, such as redbacked cutworm, have similar markings.

Figure 3. Western bean cutworm adult. Photo: Jocelyn Smith, University of Guelph.

Please help – When monitoring in the Canadian prairies, adults or larvae suspected to be western bean cutworm can be directed to your provincial entomologist for species verification. New and confirmed sightings of this species are important and will help mobilize research and pest management strategies.

Additional information on western bean cutworm can be found in the publication “Western Bean Cutworm” by the Canadian Corn Pest Coalition: https://cornpest.ca/corn-pests/western-bean-cutworm/

Did you know? Bt corn with the Vip3A protein effectively controls western bean cutworm, but some of the Bt corn products for European corn borer will not.

Reference:
Ecology and Management of the Western Bean Cutworm (Lepidoptera: Noctuidae) in Corn and Dry Beans—Revision With Focus on the Great Lakes Region. 2019. J. L. Smith, C. D. Difonzo, T. S. Baute, A. P. Michel, and C. H. Krupke, Journal of Integrated Pest Management, Volume 10, Issue 1: 1-19.

Weekly Update

Week 12 and our staff continue with surveying! This week, more warm weather continues to advance both insect and plant development. Some southern areas of the prairies are preparing to initiate harvest for their earliest crops and are carefully watching moisture meters! If you missed it, in Week 11 we thanked the many people who are busy monitoring in fields across the Canadian prairies!

Be sure to catch the Insect of the Week – it’s pea aphids!

Stay safe and good scouting to you!

Questions or problems accessing the contents of this Weekly Update?  Please contact us so we can connect you to our information. Past “Weekly Updates” can be accessed on our Weekly Update page.

Weather synopsis

TEMPERATURE: This past week (July 11 – 18, 2021) the prairies continued to experience above-average temperatures and extremely dry conditions. The warmest temperatures were observed across southern and central regions across all three prairie provinces (Fig. 1. Across the prairies, the average 30-day (June 19 – July 18, 2021) temperature was almost 4 °C warmer than climate-normal values. The warmest temperatures were observed across southern Alberta and western Saskatchewan (Fig. 2). The 2021 growing season (April 1 – July 18, 2021) has been 1.5 °C warmer than average. The warmest temperatures have occurred across southeastern Manitoba, west-central Saskatchewan and southern Alberta (Fig. 3).

Figure 1. 7-day average temperature (°C) observed across the Canadian prairies for the period of July 12 – 18, 2021.
Figure 2. 30-day average temperature (°C) observed across the Canadian prairies for the period of June 19 – July 18, 2021.
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 – July 18, 2021.

Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-July 19, 2021) can be viewed by clicking the hyperlinks. Over the past 7 days (July 14-20, 2021), the lowest temperatures recorded across the Canadian prairies ranged from < -2 to >14 °C while the highest temperatures observed ranged from <22 to >34 °C. With the incredible heat experienced so far, check the number of days of >25 °C or >30 °C across the Canadian prairies (April 1-July 20, 2021). Access these maps and more using the AAFC Drought Watch webpage interface.

PRECIPITATION: This past week significant rainfall was reported across the Peace River region (Fig. 4). Rainfall amounts for the period of June 19 – July 18 (30-day accumulation) have been well below average with most of the prairies receiving less than 40 % of the average amount for this time period (Fig. 5). Growing season precipitation has been less than average across most of the prairies. Western Saskatchewan and most of Alberta have received less than 100 mm of rain this year (Fig. 6).

Figure 4. 7-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 12 – 18, 2021.
Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 19 – July 18, 2021
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 – July 18, 2021.

The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Current Conditions Maps for the growing season. Historical weather data can be access at the AAFC Drought Watch Historical website, Environment Canada’s Historical Data website, or your provincial weather network.

Predicted grasshopper development

Model simulations were used to estimate grasshopper (Melanoplus sanguinipes) development as of July 21, 2021. Above-average temperatures in late June and July continue to result in a noticeable increase in grasshopper development. Last week, simulations indicated that most of the population was expected to be in the 4th or 5th instar stages.

This week, grasshopper populations are predicted to be mostly 5th instar (35 %) and adult (35 %) stages (Fig. 1). As a point of comparison, grasshopper development based on long-term average values for this week are 11 % (5th Instar) and 1.4 % (adults) (Fig. 2).

Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as the average developmental stage, across the Canadian prairies as of July 18, 2021.
Figure 2. Long-term average predicted grasshopper (Melanoplus sanguinipes) development, presented as the average developmental stage, across the Canadian prairies as of July 11, based on climate normals data.

Adults should be present across all three provinces and the occurrence of adults is well ahead of long-term average values (Figs. 3 and 4). The model predicts that oviposition should have begun across the southern prairies (Fig. 5).

Figure 3. Percent of grasshopper (Melanoplus sanguinipes) population in the adult stage across the Canadian prairies as of July 18, 2021.
Figure 4. Long-term average predicted grasshopper (Melanoplus sanguinipes) development, presented as the percent of the population in the adult stage, across the Canadian prairies as of July 11 (based on climate normals data).
Figure 5. Percent of grasshopper (Melanoplus sanguinipes) population in the egg stage across the Canadian prairies as of July 18, 2021.

Grasshopper Scouting Steps:
● Review grasshopper diversity and scouting information including photos of nymphs, adults, and non-grasshopper species to aid in-field scouting and accurately apply thresholds for grasshoppers.
● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.
● Start at one end in either the field or the roadside and walk toward the other end of the 50 m, making some disturbance with your feet to encourage any grasshoppers to jump.
● Grasshoppers that jump/fly through the field of view within a one-meter width in front of the observer are counted.
● A meter stick can be carried as a visual tool to give perspective for a one-meter width. However, after a few stops, one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance.
● At the endpoint, the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure.
● Compare counts to the following damage levels associated with pest species of grasshoppers:
0-2 per m² – None to very light damage
2-4 per m² – Very light damage
4-8 per m² – Light damage
8-12 per m² – Action threshold in cereals and canola
12-24 per m² – Severe damage
24 per m² – Very severe damage
For lentils at flowering and pod stages, >2 per m² will cause yield loss.
For flax at boll stages, >2 per m² will cause yield loss.
● More practically, the following thresholds are offered but, in the event of additional crop stress (e.g., drought), the use of “may be required” versus “control usually required” requires careful consideration:

Biological and monitoring information (including tips for scouting and economic thresholds) related to grasshoppers in field crops is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (accessible in either English-enhanced or French-enhanced versions).

Predicted diamondback moth development

Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. Each spring adult populations migrate northward to the Canadian prairies on wind currents from infested regions in the southern or western U.S.A. Upon arrival to the prairies, migrant diamondback moths begin to reproduce and this results in subsequent non-migrant populations that may have three or four generations during the growing season.

Model simulations to July 18, 2021, indicate that the third generation of non-migrant adults are currently emerging across the Canadian prairies (Fig. 1). Compared to long-term average data (climate normal), an additional generation of DBM are predicted to develop during the 2021 growing season!

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to occur across the Canadian prairies as of July 18, 2021.
Figure 2. Long-term average predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to occur across the Canadian prairies as of July 20 (based on climate normals data).

Monitoring: Remove plants in an area measuring 0.1 m² (about 12″ square), beat them onto a clean surface and count the number of larvae (Fig. 3) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.

Figure 3. Diamondback larva measuring ~8mm long.
Note brown head capsule and forked appearance of prolegs on posterior.

The economic threshold for diamondback moth in canola at the advanced pod stage is 20 to 30 larvae/ 0.1 m² (approximately 2-3 larvae per plant).  Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).

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Figure 4. Diamondback moth pupa within silken cocoon.
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Figure 5. Diamondback moth.

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba Agriculture and Resource Development, Saskatchewan Agriculture, and the Prairie Pest Monitoring Network.  Also, refer to the diamondback moth pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (accessible in either English-enhanced or French-enhanced versions).

Predicted wheat midge development

The recent warm temperatures have contributed to the rapid development of wheat midge populations. Where present, wheat midge populations should be predominantly in the egg and larval stages (Figs. 1 and 2). Last week the model predicted that 51 % of the population would be eggs. This past week eggs have transitioned to the larval stage and wheat midge populations will be primarily in the larval stage (54 % of the population). Larvae will be in wheat heads, feeding on developing kernels.

Figure 1. Percent of wheat midge (Sitodiplosis mosellana) population that is in the egg stage, across the Canadian prairies as of July 18, 2021.
Figure 2. Percent of wheat midge (Sitodiplosis mosellana) population that is in the larval stage (in wheat heads), across the Canadian prairies as of July 11, 2021.

The model was projected to August 3 to determine potential development at Regina (Fig. 3), Lacombe (Fig. 4), and Grande Prairie (Fig. 5) over the next two weeks. Development is similar for each location. Results indicate that larvae (Sm L1-2) are expected to complete development by the end of July, at which time they will drop to the soil and develop into larval cocoons (overwintering stage).

Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) near Regina, Saskatchewan as of July 18, 2021 (projected to August 3, 2021).
Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) near Lacombe, Alberta as of July 18, 2021 (projected to August 3, 2021).
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) near Grande Prairie, Alberta as of July 18, 2021 (projected to August 3, 2021).

Monitoring: The window for scouting and application of the economic threshold for wheat midge (i.e., during the synchrony between wheat anthesis and midge flight period) has now drawn to a close for 2021. 

Wheat midge was featured as the Insect of the Week in 2021 (for Wk07). Be sure to also review wheat midge and its doppelganger, the lauxanid fly, featured as the Insect of the Week in 2019 (for Wk11) – find descriptions and photos to help with in-field scouting!  Additionally, the differences between midges and parasitoid wasps were featured as the Insect of the Week in 2019 (for Wk12).  Remember – not all flying insects are mosquitoes nor are they pests! Many are important parasitoid wasps that actually regulate insect pest species in our field crops OR pollinators that perform valuable ecosystem services!

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Thrips in canola

Thrips in canola (Thynsanoptera) – While scouting at this time of year, curled canola pods may be encountered.  The culprits are quite possibly thrips.

Figure 1. Thrips damage observed in canola in the northeast of Saskatchewan in July 2016 (Photo: AAFC-Saskatoon, Olfert 2016).

Damage: Flower thrips (Thysanoptera) are pests of a broad range of plants including cereals and broadleaved crops such as canola. Thrips are minute, slender-bodied insects with rasping-sucking mouthparts and feed by rasping the surface of canola buds and sucking up plant fluids. 

Biology: Thrips have six life stages: egg, two larval stages, a prepupal and pupal stage and an adult. Both adults and nymphs cause damage by feeding on the flower and buds. Limited surveys in 1999 in Saskatchewan and Alberta indicated that the predominant species were Frankliniella tritici (flower thrip) followed by Thrips tabaci (onion thrip) and T. vulgatissimus (no common name).

In canola, pods damaged by thrips are often curled and tend to drop prematurely.  Some species, such as T. vulgatissimus have been credited with contributing to pollination.

Read more about thrips in canola by accessing this article by Olfert et al. 1998).

Lygus bug monitoring

On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.

Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field.  Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3). 

Figure 3. Sequential sampling for lygus bugs at late flowering stage in canola.

If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).

The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. 

Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production.  The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage.  In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.

How to tell them apart: The 2019 Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids!  Both posts include tips to discern the difference between when doing in-field scouting!

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.

Cabbage seedpod weevil

Monitoring is already underway for cabbage seedpod weevil (CSPW; Ceutorhynchus obstrictus) in southern areas of the prairies – it was the Insect of the Week for Wk08! There is one generation of CSPW per year and the overwintered adult is an ash-grey weevil measuring 3-4mm long (e.g., lower left photo).  Mating and oviposition are quickly followed by eggs hatching within developing canola pods (e.g., lower right photo). The highly concealed larvae feed within the pod, consuming the developing seeds.

Monitoring:

  • Begin sampling when the crop first enters the bud stage and continue through the flowering. 
  • Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.  
  • Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.  
  • Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.  
  • An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). 
  • Consider making insecticide applications late in the day to reduce the impact on pollinators.  Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.  
  • High numbers of adults in the fall may indicate the potential for economic infestations the following spring.

Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss.  Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo).  Eggs are oval and an opaque white, each measuring ~1mm long.  Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.

There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo).  The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds.  A single larva consumes about 5 canola seeds.  The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell.  Approximately 10 days later, the new adult emerges to feed on maturing canola pods.  Later in the season, these new adults migrate to overwintering sites beyond the field.

Albertan growers can report and check the live map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved24Jun2021).

Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.  Also refer to the cabbage seedpod weevil pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.

Bertha armyworm

Provincial insect pest monitoring networks in Manitoba, Saskatchewan and Alberta are now compiling cumulative counts of adults intercepted from the pheromone-baited green unitraps deployed in fields across the prairies. Review the Provincial Insect Pest Report Links to find summaries or link to the latest bertha armyworm moth counts by clicking the appropriate province’s reporting info for Manitoba, Saskatchewan or Alberta. So far, interception counts remain mainly in the “low risk” categories across the Canadian prairies. Review the 2020 pheromone trapping cumulative moth counts here to identify potential high risk areas to target for scouting for larvae now!

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting.  Use the images below (Fig. 1) to help identify the various stages.  Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm! 

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Figure 6. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also, refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.

West nile virus risk

The following is offered to help predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies. This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in Figure 1 but the unusual heat across the prairies greatly accelerated mosquito development!

As of July 18, 2021 (Fig. 1), C. tarsalis development continues to be most advanced in southern Manitoba, southern Alberta, and southwestern Saskatchewan. Outdoor enthusiasts falling within areas highlighted red (i.e., areas that have accumulated sufficient heat accumulation for C. tarsalis to emerge) should wear DEET to protect against WNV! Because of the continued high temperatures, areas highlighted yellow or orange in the map below (as of July 18) should also start to use DEET this week! IF C. tarsalis is present in an area where WNV is active, it may take as little as 14 days for adults to become fully infective with the current warm weather (Fig. 2).

Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 18, 2021).

The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date June 21, 2021; retrieved July 22, 2021). The screenshot below (retrieved 22Jul2021) serves as a reference and reports one human case of WNV in Ontario.

Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retried 22Jul2021).

Anyone keen to identify mosquitoes will enjoy this pictorial key for both larvae and adults which is posted on the Centre for Disease Control (CDC) website but sadly lacks a formal citation other than “MOSQUITOES: CHARACTERISTICS OF ANOPHELINES AND CULICINES prepared by Kent S. Littig and Chester J. Stojanovich” and includes Pages 134-150. The proper citation may be Stojanovich, Chester J. & Louisiana Mosquito Control Association. (1982). Mosquito control training manual. pp 152.

Pre-Harvest Intervals (PHI)

Before the harvest rush begins, start to consider pre-harvest intervals. The PHI refers to the minimum number of days between a pesticide application and swathing or straight combining of a crop.  The PHI recommends sufficient time for a pesticide to break down. PHI values are both crop- and pesticide-specific.  Adhering to the PHI is important for a number of health-related reasons but also because Canada’s export customers strictly regulate and test for the presence of trace residues of pesticides.

Here are a few resources to help:
• Information about PHI and Maximum Residue Limits (MRL) is available on the Keeping It Clean website.
• The Pest Management Regulatory Agency has a fact sheet, “Understanding Preharvest Intervals for Pesticides” or download a free PDF copy.
• Use Keeping It Clean’s “Spray to Swath Interval Calculator” to accurately estimate:
◦ PHI for canola, chickpeas, lentils, faba beans, dry beans, or peas.
◦ How long to wait, if the crop’s already been sprayed.
◦ To find a pesticide to suit your timeline.
• Provincial crop protection guides include the PHI for every pesticide x crop combination; Alberta, Saskatchewan, or Manitoba guides are downloadable as free, searchable PDF format.

Timely IOTW to review

The Insect of the Week (IOTW) was originally launched as a tool to promote field guides affiliated with PPMN Network participants and to highlight entomological species occurring in field crops across the Canadian prairies. Almost immediately, the IOTW became one of the most popular ways PPMN shares information related to insect pests, beneficial arthropods AND the entomologists who study them. A surprising array of IOTW posts are available from 2015 to the present and remain available for review and to support scouting and identification – check them out!

Provincial insect pest report links

Provincial entomologists provide insect pest updates throughout the growing season so link to their information:

MANITOBA’S Crop Pest Updates for 2021 are now available – access the July 21, 2021 report here. Be sure to bookmark their Crop Pest Update Index to readily access these reports! Bookmark their insect pest homepage to access fact sheets and more!
• Bertha armyworm pheromone trap monitoring update for MB – Cumulative counts arising from weekly data are available here. Cumulative counts are categorized as “low risk” so far (i.e., 0-300 moths).
• Diamondback moth pheromone trap monitoring update for MB – Trapping has drawn to a close for 2021. Access the summary here. Only 65 traps intercepted moths and the highest cumulative count was 171 moths near Selkirk. Access the summary (as of June 30, 2021). At this point, in-field scouting for larvae remains important.

SASKATCHEWAN’S Crop Production News is available. Access Issue #3 online which includes a crop protection lab update, describes a new program to monitor european corn borer, and information related to pollinator planning in crop production. Be sure to bookmark their insect pest homepage to access important information!
• Bertha armyworm pheromone trap monitoring update for SK – Cumulative counts arising from weekly data is now available here.
• Diamondback moth pheromone trap monitoring update for SK – Monitoring has drawn to a close for 2021. Review the final DBM counts. Extremely low numbers have been intercepted. Province-wide, <65 moths have been intercepted (2021Jun28 Carter, pers. comm.). At this point, in-field scouting for larvae remains important.

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, and insect trap set-up videos and more. There is also a Major Crops Insect webpage. The new webpage does not replace the Insect Pest Monitoring Network page. Remember, AAF’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
• Wheat midge pheromone trap monitoring update for AB – Cumulative counts arising from weekly data are available so refer to the Live Map.
• Cabbage seedpod weevil sweep-net monitoring update for AB – In-field counts can be entered here to populate the Live Map. Some sites in southern Alberta are reporting densities at or above the economic threshold in canola (22Jul2021).
• Bertha armyworm pheromone trap monitoring update for AB – Cumulative counts arising from weekly data have begun so refer to the Live Map. Cumulative counts throughout the province report “low risk” numbers of moths so far (22Jul2021).
• Diamondback moth pheromone trap monitoring update for AB – Trapping has drawn to a close for 2021. Refer to the Live Map which reports extremely low numbers of moths intercepted so far (<50 province-wide as of 01Jul2021). At this point, in-field scouting for larvae remains important.
• Cutworm reporting tool – Refer to the Live Map which now reports seven sites with cutworms (as of 01Jul2021).

Crop report links

Click the provincial name below to link to online crop reports produced by:
• Manitoba Agriculture and Resource Development (subscribe to receive OR access a PDF copy of the July 20 2021 report).
• Saskatchewan Agriculture (or access a PDF copy of the July 13-19, 2021 report).
• Alberta Agriculture and Forestry (or access a PDF copy of the July 13, 2021 report).

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 19, 2021 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 20, 2021 edition).

Previous posts

As the growing season progresses, the various Weekly Update topics move on and off the priority list for in-field scouting but they should be kept at hand to support season-long monitoring. Click to review these earlier 2021 Posts (organized alphabetically):
• 2020-2021 Risk and forecast maps
• Alfalfa weevil – predicted development (Wk07)
• Aphids in field crops (Wk09)
• Bertha armyworm – predicted development (Wk09)
• Cabbage seedpod weevil monitoring (Wk09)
• Cereal aphid manager APP (Wk07)
• Cereal leaf beetle – predicted development (Wk07)
• Crop protection guides (Wk03)
• Cutworms (Wk02)
• European corn borer – nation-wide monitoring project (Wk07)
• Field heroes (Wk08)
• Flea beetles (Wk02)
• Flea beetles – predicted geographic distribution and abundance (Wk04)
• Grasshopper diversity and scouting photos (Wk08)
• Ladybird beetles (Wk03)
• Lygus bug monitoring (Wk09)
• Midges in canola (Wk11)
• Monarch migration (Wk09)
• Pea leaf weevil (Wk03)
• Scouting charts – canola and flax (Wk03)
• Slugs and their parasites (Wk04)
• Weather radar mapping interface (Wk06)
• Wind trajectories for monitoring insect movement (Wk02)
• Wind trajectories – weekly reports (Wk09)
• Wireworms (Wk02)

PEA APHIDS: A PERSISTENT PROBLEM FOR LEGUME GROWERS

Pea aphid (AAFC)

Native to Europe, pea aphids were discovered in Ontario during the late 1800s and continued west into the Prairie region. True to their name, pea aphids consume legumes like field peas, alfalfa, broad beans, chickpeas, lentils and clover. Overwintering as eggs on perennial legumes like alfalfa and clover, pea aphids reproduce asexually until winged females migrate to summer crop hosts to generate several new generations over the growing season.

Pea aphid damage to peas occurs when the insects feed during the flowering and early pod stage, resulting in reduced crop yield due to delayed seed formation and smaller seed size. In alfalfa crops, pea aphids feed on the stems and expanding leaves, stunting overall plant growth and causing the leaves to yellow. Infested alfalfa is more susceptible to cold damage during the winter months.

Adults are long-legged and pear-shaped, between 3-4 millimetres long. Colour varies between light to dark green, and each antennal segment is tipped with a black band. Pea aphid nymphs have a similar appearance but are somewhat smaller.

Pea aphid adults and nymph (AAFC)

Biological and monitoring information related to pea aphids in field crops can be found on our Monitoring page as well as on the Manitoba Agriculture and Resource Development website. For more information, visit the pea aphid page in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).

Weather synopsis

The 2020 growing season, April 1 – July 12, 2020, has been cooler and wetter than normal across many locations in Alberta and Saskatchewan. Conditions in Manitoba have been warmer and dryer than normal. This past week (July 6-12, 2020) prairie temperatures were warmest in Manitoba and eastern Saskatchewan (Table 1; Fig. 1). Average 7-day temperatures continue to be warmest across Manitoba and eastern Saskatchewan and coolest across most of Alberta (Table 1; Fig. 1).

Figure 1. Observed average temperatures across the Canadian prairies the past seven days (July 6-12, 2020).

Average 30-day (June 13-July 12, 2020) temperatures continue to be cooler in Alberta than in southern Saskatchewan and Manitoba (Table 2; Fig. 2). The average 30-day temperature at Winnipeg and Brandon continued to be greater than locations in Alberta and Saskatchewan (Fig. 2). Temperature anomalies indicate that temperatures have been below normal across most of Alberta and Saskatchewan and were 0 to 2 °C warmer than average across eastern Saskatchewan and southern Manitoba (Table 2; Fig. 3). Based on growing season temperatures (April 1 – July 12, 2020), conditions have been warmest for southern locations (Table 3).

Figure 2. Observed average temperatures across the Canadian prairies the past 30 days (June 13-July 12, 2020).
Figure 3. Mean temperature difference from Normal the past 30 days (June 16-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (13Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

Cumulative rainfall for the past 7 days was lowest across southern regions of Alberta and across most of Manitoba (Table 1 Fig. 4). Lethbridge reported 4.2 mm and Winnipeg reported 1.4 mm (Table 1). Cumulative 30 day rainfall continued to be greatest across central regions of Alberta (Table 2; Fig. 5). Rainfall amounts were lowest across southern regions of the prairies (Table 2; Fig. 5).

Figure 4. Observed cumulative precipitation across the Canadian prairies the past seven days (July 6-12, 2020).

Total 30-day rainfall at Brandon, Winnipeg and Swift Current was less than 100 mm (Table 2; Fig. 5). Lethbridge has reported 122.3 mm (261% of normal) in the past 30 days (Table 2). Growing season rainfall (percent of average) is below normal across eastern Saskatchewan and localized areas of Manitoba.

Figure 5. Observed cumulative precipitation across the Canadian prairies the past 30 days (June 13-July 12, 2020).
Figure 6. Percent of average precipitation for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (14Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 5 ºC, April 1-July 13, 2020) is below (Fig. 7):

Figure 7. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The growing degree day map (GDD) (Base 10 ºC, April 1-July 13, 2020) is below (Fig. 8):

Figure 8. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The highest temperatures (°C) observed the past seven days ranged from <15 to >33 °C in the map below (Fig. 9).

Figure 9. Highest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-July 13, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (16Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

The maps above are all produced by Agriculture and Agri-Food Canada. Growers can bookmark the AAFC Current Conditions Drought Watch Maps for the growing season. Historical weather data can be access at the AAFC Drought Watch website, Environment Canada’s Historical Data website, or your provincial weather network.

Predicted bertha armyworm development

Model simulations for July 12, 2020 indicate that 35% of the population is in the egg stage (37% last week) and 65% of the population is in the larval stages (14% last week). Across the Parkland and Peace River regions, BAW populations are predicted to be primarily in the egg stage (Fig. 1). Populations across southern regions are primarily in the larval stage (Fig. 1).

Figure 1. Predicted percent of bertha armyworm (Mamestra configurata) population in the larval stage as of July 12, 2020.

The two graphs below demonstrate that larval development near Brandon is predicted to be ahead of fields near Grande Prairie. In Brandon, populations are primarily in the larval stage (Fig. 2) while BAW populations near Grande Prairie are predicted to be predominantly in adult and egg stages (Fig. 3).

Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Brandon MB as of July 12, 2020.
Figure 3. Predicted bertha armyworm (Mamestra configurata) phenology at Grande Prairie AB as of July 12, 2020.
Figure 5. The egg stage (A), larval stage (B), pupal stage (C), and adult stage (D) of bertha armyworm. Photos: Jonathon Williams (AAFC-Saskatoon).

Weekly Pheromone-baited Trapping Results – Early season detection of bertha armyworm is improved through the use of pheromone-baited unitraps traps deployed in fields across the Canadian prairies.  Click each province name to access moth reporting numbers observed in Alberta, Saskatchewan and Manitoba (as they become available). Check these sites to assess cumulative counts and relative risk in your geographic region but remember in-field scouting is how the economic threshold is applied to manage this pest.

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting.  Use the images above (Fig. 5) to help identify the economically important larvae.  Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm! 

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted wheat midge development

Wheat midge model runs indicate that, where wheat midge are present, adult emergence is well underway and oviposition is occurring across most prairie locations. The map suggests that, as of July 12, 2020, populations are primarily in the egg stage (Fig. 1). Low rainfall amounts across large areas of Manitoba and Saskatchewan has resulted in delayed adult emergence, resulting in lower egg densities.

Figure 1. Predicted percent of population of wheat midge (Sitodiplosis mosellana) at adult stage across the Canadian prairies (as of July 12, 2020).

The next 10-14 days are very important for monitoring wheat midge populations for the purpose of making management decisions. Simulations were run to July 26 to assess population development over the next 10 days (Table 1). The following table indicates that 50% emergence of adults should occur this week at Saskatoon and next week at Lacombe (Table 1). This week populations in Manitoba are predicted to be at 90% adult emergence (Table 1).

The two graphs below illustrate the development of wheat midge populations near Saskatoon (Fig. 2) and Lacombe (Fig. 3). Adult numbers are currently peaking near Saskatoon while adult emergence near Lacombe is not expected to peak until next week.

Figure 2. Predicted wheat midge (Sitodiplosis mosellana) phenology at Saskatoon SK projected to July 21, 2020.
Figure 3. Predicted wheat midge (Sitodiplosis mosellana) phenology at Lacombe AB projected to July 21, 2020.

The next two graphs compare the synchrony between wheat midge and wheat for fields near Lacombe (Fig. 4). The graph indicates that peak adult emergence and oviposition may occur during anthesis; wheat susceptibility decreases once the crop is flowering (Fig. 4).

Figure 4. Comparison of predicted phenology of wheat midge (Sitodiplosis mosellana) and wheat at Lacombe AB projected to July 21, 2020.

The last graph compares phenology (Saskatoon) of wheat midge adults with Macroglenes penetrans, a parasitoid of wheat midge (Fig. 5). The parasitoid wasp lays eggs in wheat midge eggs. The graph shows that emergence/oviposition of wheat midge adults and M. penetrans are similar (Fig. 5). This information can be used as a guide to determine when fields should be monitored.

Figure 5. Comparison of predicted phenology of wheat midge (Sitodiplosis mosellana) and its parasitoid, Macroglenes penetrans, at Saskatoon SK projected to July 21, 2020.

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

More information about Wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Predicted grasshopper development

As of July 12, 2020, the grasshopper model estimates that development across the prairies ranges from 1st instar stage to adults. Based on the model simulations, development has been slowest in the Peace River region where average nymph development ranges between the 2nd and 3rd instars (Fig. 1; Table 1). Across the southern prairies, the majority of the nymph population is predicted to be in the 3rd to 5th instar stages, with adults predicted to occur across southern Manitoba where populations are active (Fig. 1; Table 1). Across the prairies, populations are predicted to be 6, 6, 11, 27, 24, 21 and 5% in egg, first, second, third, fourth, fifth and adult stages, respectively.

Figure 1. Predicted average instar stages of grasshopper (Melanoplus sanguinipes) populations across the Canadian prairies (as of July 12, 2020).

Table 1 indicates that predicted development at Brandon and Winnipeg is well ahead of Lacombe and Grande Prairie. The two graphs compare grasshopper development in Saskatoon (Fig. 2) and Winnipeg (Fig. 3). Grasshopper populations near Saskatoon are predominantly in the 4th and 5th instars with first appearance of adults beginning to occur (Fig. 2). Populations near Winnipeg are expected to be primarily adults (Fig. 3).

Figure 2. Predicted grasshopper (Melanoplus sanguinipes) phenology at Saskatoon SK. Values are based on model simulations (April 1-July 12, 2020).
Figure 3. Predicted grasshopper (Melanoplus sanguinipes) phenology at Winnipeg MB. Values are based on model simulations (April 1-July 12, 2020).

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (Philip et al. 2018) as an English-enhanced or French-enhanced version. 

Lygus bug monitoring

On the Canadian prairies, lygus bugs (Heteroptera: Miridae) are normally a complex of several native species usually including Lygus lineolaris, L. keltoni, L. borealis, L. elisus although several more species are distributed throughout Canada. The species of Lygus forming the “complex” can vary by host plant, by region or even seasonally.

Lygus bugs are polyphagous (i.e., feed on plants belonging to several Families of plants) and multivoltine (i.e., capable of producing multiple generations per year). Both the adult (Fig. 1) and five nymphal instar stages (Fig. 2) are a sucking insect. Adults overwinter in northern climates. The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Figure 2. Fifth instar lygus bug nymph (3-4 mm long) (photo: AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. In canola, lygus bugs feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind: Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20 °C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180 ° sweeps. Count the number of lygus bugs in the net. Sampling becomes more representative IF repeated at multiple spots within a field so sweep in at least 10 locations within a field to estimate the density of lygus bugs. In fact, sampling is most accurate when repeated at a total of 15 spots within the field.  Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure 3). 

Figure 3. Sequential sampling for lygus bugs at late flowering stage in canola.

If the total number is below the lower threshold line (Fig. 3), no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold tables (Tables 1 and 2).

The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted. Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. 

Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production.  The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage.  In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.

How to tell them apart: The 2019 Insect of the Week’s doppelganger for Wk 15 was lygus bug versus the alfalfa plant bug while Wk 16 featured lygus bug nymphs vs. aphids!  Both posts include tips to to discern the difference between when doing in-field scouting!

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English or French versions are available.

Field heroes

The Field Heroes campaign continues to raise awareness of the role of beneficial insects in western Canadian crops. Check the recently updated Field Heroes website for scouting guides, downloadable posters, and videos. Learn about these important organisms at work in your fields!  

Real Agriculture went live in 2020 with a Pest and Predators podcast series!

• Access Episode 1 – Do you know your field heroes? Jennifer Otani (Agriculture and Agri-Food Canada-Beaverlodge) and Shaun Haney (RealAg). Published online May 12, 2020.

• Access Episode 2 – An inside look at the Prairie Pest Monitoring Network. Meghan Vankosky (Agriculture and Agri-Food Canada-Saskatoon) and Shaun Haney (RealAg). Published online May 26, 2020.

• Access Episode 3 – How much can one wasp save you? Haley Catton (Agriculture and Agri-Food Canada-Lethbridge) and Shaun Haney (RealAg). Published online June 9, 2020.

• Access Episode 4 – Eat and be eaten — grasshoppers as pests and food John Gavloski (Manitoba Agriculture and Resource Development) and Shaun Haney (RealAg). Published online June 23, 2020.

• Access Episode 5 – Killer wasp has only one target — wheat stem sawfly Scott Meers (Mayland Consulting) and Shaun Haney (RealAg). Published online July 7, 2020.

Access ALL the Field Heroes links here and be sure to follow @FieldHeroes!

West nile virus risk

Health Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance.  Link here to access the most current weekly update (July 4, 2020). The screenshot below was retrieved 16Jul2020 as reference but access that information here.

This image has an empty alt attribute; its file name is 2020Jun28-Jul04_WNV_Weekly_HealthCanada-1024x593.png

The following is offered to predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies (Fig. 1). This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in the map below (yellow, orange then red highlighted areas).  As of July 13, 2020, areas highlighted yellow and more imminently orange are approaching sufficient heat accumulation for mosquitoes to emerge.  Plan to protect yourself by wearing DEET!  

Figure 1. Predicted development of Culex tarsalis, across the Canadian prairies (as of July 13, 2020).

Provincial insect pest report links

Provincial entomologists provide insect pest updates throughout the growing season so link to their information: 

• Manitoba‘s Crop Pest Updates for 2020 are available. Access the July 15, 2020 report. The summary indicates that, “Armyworms and grasshoppers continue to be the biggest insects concern on crops in Manitoba. Scouting for diamondback moth continues, with just one report of spraying for diamondback moth. Spraying for goosefoot groundling moth and a stem borer maggot has been reported from quinoa. Green cloverworm has been found on soybeans in eastern Manitoba, but not at levels that would be economical. Pupal clusters of Cotesia, a parasitoid of armyworms and other caterpillars, have been reported to be quite abundant in some of the fields that had armyworms.”

• Saskatchewan‘s Crop Production News and read Issue 5 which includes articles on Bertha armyworm, Cabbage seedpod weevil,  FieldWatch – Fostering Communication Between Applicators and Producers, and Look What the Wind Blew in! Diamondback Moths Arrived Early This Spring. Issue #4 included articles on Pest Scouting 101: Mid-Summer, and The Wheat Midge.

•  Alberta Agriculture and Forestry’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.

Crop report links

Click the provincial name below to link to online crop reports produced by:

• Manitoba Agriculture and Rural Initiatives – Other viewing options include subscribing to receive or access a PDF of July 14, 2020 report.

• Saskatchewan Agriculture  or access a PDF of July 7-13, 2020 report.

• Alberta Agriculture and Forestry or access a PDF of June 29, 2020 report.

The following crop reports are also available:

• The United States Department of Agriculture (USDA) produces a Crop Progress Report (read the July 13, 2020 edition).

• The USDA’s Weekly Weather and Crop Bulletin (read the July 14, 2020 edition). 

Previous posts

Click to review these earlier 2020 Posts (organized alphabetically):

    • 2019-2020 Risk and forecast maps

    • Alfalfa weevil (Wk08)

    • Aster leafhopper (Wk05)

    • Beetle data please! (Wk03)

    • Cereal aphid APP (Wk11)

    • Crop protection guides (Wk02)

    • Cutworms (Wk02)

    • Diamondback moth (Wk11)

    • Flea beetles (Wk02)

    • John Doane (Wk10)

    • Monarch migration (Wk10)

    • Pea leaf weevil (Wk11)

    • Pea leaf weevil – predicted development (Wk09)

    • Prairie provincial insect webpages (Wk02)

    • Scouting charts – canola and flax (Wk02)

    • Ticks and Lyme Disease (Wk06)

    • Wind trajectories (Wk09)

Alfalfa Pests / Feature Entomologist: Tyler Wist

This week’s Insect of the Week featured crop is alfalfa: a perennial legume known as “the Queen of Forage Crops.” Our feature entomologist this week is Tyler Wist.

Alfalfa – AAFC

A crop indispensable to Canadian livestock production, alfalfa is a high protein forage used for pasture, hay and silage. Since 1950, improved alfalfa cultivars have been developed for growth in the Prairie region. In particular, Variegated alfalfa is a subspecies developed by cross breeding Flemish alfalfa with Siberian alfalfa. The resulting cultivar is known for both its winter hardiness and resilience to drought and is grown across Western Canada. Because alfalfa is so integral to livestock industries, alfalfa seed is a notable Canadian export, with almost all seed production occurring in Manitoba, Saskatchewan and Alberta.

Several pest insects target alfalfa. Monitoring and scouting protocols as well as economic thresholds (when available) are found in Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management and the Cutworm Pests of Crops on the Canadian Prairies: Identification and Management Field Guide. Additional monitoring protocols exist to control certain pests.

Alfalfa field – AAFC
Alfalfa Pests
  • Alfalfa blotch leafminer
  • Alfalfa caterpillar
  • Alfalfa looper
  • Alfalfa weevil
  • Army cutworm
  • Armyworm
  • Aster leafhopper
  • Beet webworm
  • Bertha armyworm
  • Black cutworm
  • Black grass bugs
  • Blister beetles
  • Clover leaf weevils
  • Clover root weevils
  • Dingy cutworm
  • Fall field cricket
  • Grasshoppers
  • Green cloverworm
  • Lygus bugs
  • Mormon cricket
  • Pale western cutworm
  • Pea aphid
  • Pea leaf weevil
  • Potato leaf weevil
  • Potato leafhopper
  • Redbacked cutworm
  • Saltmarsh caterpillar
  • Superb stink bug
  • Sweetclover weevil
  • Twospotted spider mite
  • Variegated cutworm
Alfalfa looper – AAFC

Entomologist of the Week: Tyler Wist

Name: Tyler Wist
Affiliation: Agriculture and Agri-Food Canada Saskatoon Research and Development Centre
Contact Information: Tyler.Wist@agr.gc.ca

How do you contribute in insect monitoring or surveillance on the Prairies?

I’m involved in insect surveillance, including a project to ground-truth the use of wind trajectories to predict the arrival of aster leafhoppers (and diamondback moths) in the spring. I also monitor for aphids in cereals and pea crops in July and August as part of projects that I run as a Field Crop Entomologist with AAFC.

In your opinion, what is the most interesting field crop pest on the Prairies?

I’ve always been fascinated by aphids because in North America, our pest species are all female. Unlike the majority of insects, these female aphids are born pregnant and they give birth to live, ready-to eat your crop, clones of themselves. Those freshly-birthed offspring already have little clones of themselves starting to mature within them. Thanks to this reproductive strategy, aphid populations can increase quickly and overwhelm their host plants. Right now I’m really interested in pea aphids and their effect on lentils and faba bean. We had high enough pea aphid pressure in my plots last season (2019) that many of our plots yielded nothing which reinforces that this insect is worth studying in these crops.

What is your favourite beneficial insect?

My favourite beneficial insect is the green lacewing larva, which is a generalist predator, so generalist that one once tried to eat me. It is such a fierce predator that female green lacewings have to lay their eggs on the underside of leaves on stalks so that the first-hatched green lacewing larvae do not eat their siblings! The lacewing larva feeds by piercing it’s prey with huge mandibles, then injects a digestive enzyme that liquefies the prey inside its hard, outer exoskeleton. Once their food is liquefied, the larva proceeds to suck the prey dry until all that remains is an empty shell of the insect prey. 

Tell us about an important project you are working on right now.

I’ve alluded to two projects already, one funded by WGRF to look at the origins and arrivals of aster leafhoppers to the prairies and see if they are flying in on the same winds as the diamondback moth and one funded by ADF and WGRF to evaluate the yield loss caused by pea aphids. Another important project is to find alternative wheat resistance against wheat midge so that agriculture is not so heavily reliant on using wheat with the Sm1 gene.

What tools, platforms, etc. do you use to communicate with your stakeholders?

I communicate to stakeholders with reports to funding agencies, PowerPoint presentations at grower/agronomist meetings, using Twitter, email and sometimes even over the phone!

Weather synopsis

Temperatures this week, June 18-24, 2019, were similar to last week. Over the past seven days temperatures were cooler than normal. The warmest temperatures were observed across MB while temperatures were cooler in western SK and across AB (Fig. 1). The is a complete reversal to last week.  

Figure 1. Average temperature (°C) across the Canadian prairies the past seven days (June 16-24 2019).

Average 30 day temperatures were warmest across southern MB and SK (Fig. 2). Cooler temperatures were reported across eastern and northern AB. The mean temperature differences from normal (May 21 – June 17, 2019) have been zero to two °C warmer than normal for AB and SK while temperatures in MB have been zero to two °C cooler than normal (Fig. 3). 

Figure 2. Average temperature (°C) across the Canadian prairies the past 30 days (May 26-June 24 2019).
Figure 3. Mean temperature difference from Normal across the Canadian prairies over the past 30 days (to June 17, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (25Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

Growing season temperatures (April 1-June 24, 2019) have been warmest across the southern prairies (Fig. 4). The warmest growing season temperatures have been reported for southern AB and an area south of Winnipeg MB. Across the prairies, the average growing season temperature has been 1.2 °C below normal.

Figure 4. Average temperature (°C) across the Canadian prairies for the growing season (April 1-June 24 2019).

This past week significant rainfall amounts were reported for most of SK and across central  regions of AB (Fig. 5). Across the prairies, rainfall amounts for the past 30 days (May 26 – June 24, 2019) have been near normal (Fig. 6). The Edmonton region has been the wettest. 

Figure 5. Cumulative precipitation observed the past seven days across the Canadian prairies (June 18-24 2019).
Figure 6. Cumulative precipitation observed the past 30 days across the Canadian prairies (May 26-June 24, 2019).
Figure 7. Cumulative precipitation observed for the growing season (April 1-June 24, 2019) across the Canadian prairies.
Figure 8. Modeled soil moisture (%) across the Canadian prairies as of June 24, 2019.

The growing degree day map (GDD) (Base 5 ºC, April 1-June 24, 2019) is below (Fig. 9):

Figure 9. Growing degree day (Base 5 ºC) across the Canadian prairies for the growing season (April 1-June 24 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (25Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The growing degree day map (GDD) (Base 10 ºC, April 1-June 24, 2019) is below (Fig. 10):

Figure 10. Growing degree day (Base 10 ºC) across the Canadian prairies for the growing season (April 1-June 24, 2019).Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (25Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The lowest temperatures (°C) observed the past seven days ranged from about 11 to 0 °C in the map below (Fig. 11).

Figure 11. Lowest temperatures (°C) observed across the Canadian prairies the past seven days (to June 24, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (25Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The highest temperatures (°C) observed the past seven days ranged from about 16 to at least 27 °C in the map below (Fig. 12).

Figure 12. Highest temperatures (°C) observed across the Canadian prairies the past seven days (to June 24, 2019).  
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (24Jun2019).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers can bookmark the AAFC Drought Watch Maps for the growing season.

Predicted grasshopper development

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).

Across the prairies the grasshopper hatch is well underway with most locations having approximately 27% of the population in the egg stage. Based on model runs, approximately 33% (30% last week) of the population is in the first instar, 26% (14.5% last week) is predicted to be in the second instar, and 11% (4.3% last week) in the third instar and just over 1% are predicted to be in the fourth instar.   The following map indicates that grasshopper populations across the southern prairie are mostly in the second instar.

Figure 1. Predicted development stages of grasshopper (Melanoplus sanguinipes) populations across the Canadian prairies (as of June 24, 2019). 

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is available as a free downloadable document in either an English-enhanced or French-enhanced version.

Predicted bertha armyworm development

Bertha armyworm (Lepidoptera: Mamestra configurata) – Bertha armyworm adults should be emerging across the prairies and oviposition is predicted to have begun across most of the southern prairie regions of SK, AB and MB (Fig. 1).

Figure 1.  Predicted precent of bertha armyworm (Mamestra configurata)  populations at EGG STAGE across the Canadian prairies as of June 24 2019. 

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network. Also refer to the bertha armyworm pages within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” which is a free downloadable document as both an English-enhanced or French-enhanced version.

Again, thanks to John Gavloski (Manitoba Agriculture) who helped update the PPMN Bertha armyworm monitoring protocol.  Use the images below (Fig. 2) to help identify moths from the by-catch that will be retained in phermone-baited unitraps.

Figure 2. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D).
Photos: J. Williams (Agriculture and Agri-Food Canada)

Also be sure to review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!

Wheat midge

Wheat Midge (Sitodiplosis mosellana) –  Wheat midge and its doppelganger, the lauxanid fly, were featured as the Insect of the Week (for Wk10).  Check that post for help with in-field scouting for this economic pest of wheat!  The differences between midges and parasitoid wasps are featured as the current Insect of the Week (for Wk11).  Not all flying insects are mosquitoes nor are they pests – many are important parasitoid wasps that actually regulate insect pest species in our field crops.

Wheat midge adults generally emerge during the first week of July. Compared to long term normal values for temperature and rainfall, May and June in the Saskatoon region has been approximately 1 °C cooler and rainfall is 40-60% less than normal. Dry conditions in May and June can have significant impact on wheat midge emergence. Insufficient rainfall in May and June can result in delayed movement of larvae to the soil surface. Elliott et al (2009) reported that wheat midge emergence was delayed or erratic  if rainfall did not exceed  20-30 mm  during May. Olfert et al. 2016 ran model simulations to demonstrate how rainfall impacts wheat midge population density. Our wheat midge model indicates that dry conditions may result in:

  • Delayed adult emergence and oviposition
  • Reduced numbers of adults and eggs

The wheat midge model indicates that 70% (82% last week) of the population are in the larval  cocoon stage and 29% (18% last week) of the population is predicted to have moved to the soil surface. The first map presents wheat midge development as of last week (Fig. 1). 

Figure 1.  Percent of larval population at the soil surface (as of June 17, 2019) across the Canadian prairies.

Results indicate that dry conditions delayed development of larval cocoons in SK. Adequate precipitation in AB and MB should have resulted in movement of larvae to the soil surface.  The model indicates that recent rain has resulted in larval development (larval cocoons) across SK. The second map indicates that recent rain in SK should result in development of larval cocoons and subsequent movement of larvae to the soil surface (Fig. 2). The third map (Fig. 3) indicates that pupae may be present in some fields in southern AB and MB. It should be noted that, based on fall surveys in 2018, wheat midge populations were expected to be low across most of AB and SK.

Figure 2. Percent of larval population at the soil surface (as of June 24, 2019) across the Canadian prairies.
Figure 3.  Percent of  population AT PUPAL STAGE (as of June 24, 2019) across the Canadian prairies.

Monitoring:
When monitoring wheat fields, pay attention to the synchrony between flying midge and anthesis.

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (photographed by AAFC-Beav-S. Dufton & A. Jorgensen below). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (photographed by AAFC-Beav-S. Dufton below), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember your insecticide control options for wheat midge also kill these beneficial insects which help reduce midge populations.

Economic Thresholds for Wheat Midge:
a) To maintain optimum grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) For yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.

Inspect the developing kernels for the presence of larvae and the larval damage. 

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  

NEW – Alberta Agriculture and Forestry has also released a YouTube video describing in-field monitoring for wheat midge this week.  

More information about Wheat midge can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Cereal Aphid Manager (CAM)

Reminder  and Congratulations!  The Cereal Aphid Management (CAM) Mobile Application Team was recognized with an Agriculture and Agri-Food Canada Gold Harvest Award this month!  Team members included Ashraf Eid, Paul Faure, John Gavloski, François Jodoin, Elham Karimi, Eric Li, Jackson Macdonald, Nancy MacDonald, Owen Olfert, Chrystel Y. Olivier, Daniel Shen, Erl Svendsen, Gabriel Tobian, Tyler J. Wist.  

“The app is a culmination of innovative thinking, extensive research, and most importantly collaboration in order to design a tool that met the needs of the farming community. The team’s ability to work together and build this application will result in economic savings, a greener environment, and increased crop quality in the food production industry.”

The Cereal Aphid Manager is an easy-to-use mobile app that helps farmers and crop advisors control aphid populations in wheat, barley, oat or rye. It is based on Dr. Tyler Wist’s (AAFC-Saskatoon) innovative Dynamic Action Threshold model. The model treats the grain field as an ecosystem and takes into account many complex biological interactions including:

  • the number of aphids observed and how quickly they reproduce
  • the number of different natural enemies of aphids in the field and how many aphids they eat or parasitize per day
  • the lifecycles of aphids and their enemies taking into account developmental stages, egg laying behaviour, population growth rate, lifespan, etc.

By taking into consideration factors like these, the app predicts what the aphid population will be in seven days and the best time to apply insecticide based on economic thresholds.

Available in iOS and Android.

To learn more and to download, go to AAFC’s CAM webpage.

Note: Cereal aphids can blow up from the South at any time which cannot be predicted by the app. Therefore, farmers and crop advisors should regularly check fields during the growing season regardless of what Cereal Aphid Manager Mobile may recommend.

CAM Homepage
CAM monitoring report and recommendation
CAM icon

Provincial Insect Pest Report Links

Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information: 

• Manitoba‘s Insect and Disease Updates for 2019 are posted here. Access Update #4 posted June 12, 2019.

• Saskatchewan‘s Crops Blog Posts includes a segment on “Early season scouting of cutworms” by Sara Doerksen posted in April 2019 and “Economic thresholds” by Kaeley Kindrachuk posted in May 2019. Also access the Crop Production News with Issues #1 (featuring Diamondback moth monitoring), #2 (featuring Pest surveying and Pea leaf weevil in peas and faba beans), and #3 (featuring Bertha armyworm and Pea leaf weevil information).

•  Alberta Agriculture and Forestry’s Call of the Land regularly includes insect pest updates from Mr. Scott Meers. The most recent Call of the Land was posted March 18-22, 2019 but did not include an insect update. In the meantime, try Agri-News to access the June 10, 2019 edition including information pertaining to the value of in-field monitoring.

Crop report links

Crop reports are produced by:

The following crop reports are also available:

Field Events – Speak to an entomologist

Public summer field events – Coming to a field near you –  Prairie field crop entomologists are already scheduled to be at these 2019 field tour events from May-August (be sure to re-confirm dates and details as events are finalized):

•  June 26, 2019: 2019 CanolaPALOOZA to be held at the Lacombe Research and Development Centre (Lacombe AB).  View event info/registration details.  Entomologists tentatively participating: Jennifer Otani, Amanda Jorgensen, Meghan Vankosky, Scott Meers, Patty Reid, Sunil Shivananjappa, Hector Carcamo, Julie Soroka, Mark Cutts, Jim Tansey, Sherrie Benson and the Junior Entomologists.

•  July 9-12, July 16-18, 2019: Crop Diagnostic School. Held at the University of Manitoba Research Farm at Carman, Manitoba. An 2-week diagnostic school will complete units on entomology, plant pathology, weed science, soil fertility, pulse crop production, and oilseed production. View registration and event information. Entomologists participating: John Gavloski and Jordan Bannerman.

•  July 9, 2019: CanolaPALOOZA Saskatoon, to be held at the SRDC Llewellyn Farm. Read more about this event.  Entomologists presenting: Tyler Wist, James Tansey, Greg Sekulic, Meghan Vankosky

•  July 22, 2019: Pulse grower gathering held near Three Hills AB.  Check Alberta Pulse Growers Event Page for more information.  Entomologists presenting: Graduate students from Dr. Maya Evenden’s (U of A) working on pea leaf weevil.

•  July 23-24, 2019: Crop Diagnostic School, Scott Saskatchewan. Read more about this event.  Entomologists presenting: Meghan Vankosky, Tyler Wist.

•  July 24, 2019: Crops-a-Palooza. Held at Canada-Manitoba Crop Diversification Centre (CMCDC), Carberry, Manitoba. Read more about this event. Entomologist participating: John Gavloski, Vincent Hervet, Tharshi Nagalingam, Bryan Cassone.

•  August 8, 2019:  2019 Wheatstalk to be held at Teepee Creek AB.  View event info/registration details.   Entomologists tentatively participating: Jennifer Otani, Amanda Jorgensen, Boyd Mori.

•  August 8, 2019. Horticulture School. Agriculture and Agri-Food Canada Research Farm, Portage la Prairie, Manitoba. View event info/registration details.  Entomologist presenting: John Gavloski, Kyle Bobiwash.

Previous Posts

Click to review these earlier 2019 Posts:

2019 Risk and forecast maps – Week 2

Alfalfa weevil – Week 11

Bertha armyworm – Week 11

Cabbage seedpod weevil – Week 11
Cereal aphid APP – Week 10
Cereal leaf beetle – Week 9
Crop protection guides – Week 6
Cutworms – Week 5

Field heroes – Week 6
Flea beetles – Week 5

Grasshoppers – Week 10

Insect scouting chart for Canola – Week 5
Insect scouting chart for Flax – Week 5

Monarch migration – Week 11

Painted lady butterfly – Week 8
Pea leaf weevil – Week 10
Prairie Crop Disease Monitoring Network – Week 11

Ticks and Lyme disease – Week 4

Weather Radar – Week 6
Wildfires – Week 8

Wind trajectories – Review Page for list of PDFs

Doppelgangers: midge vs. parasitoid

The case of the innocuous versus the evil twin: When making pest management decisions, be sure that the suspect is actually a pest. This can be challenge since insects often mimic each other or look very similar. An insect that looks, moves and acts like a pest may in fact be a look-alike or doppelganger. 

Doppelgangers may be related (e.g. same genus) or may not be related, as in the case of monarch butterflies (Danaus plexippus) and viceroys (Limenitis achrippus). Doppelgangers are  usually relatively harmless but sometimes the doppelganger is a pest yet their behaviour, lifecycle or hosts may be different. 

Correctly identifying a pest enables selection of the most accurate scouting or monitoring protocol. Identification and monitoring enables the application of economic thresholds. It also enables a producer to select and apply the most effective control option(s) including method and timing of application.  For the rest of the growing season, the Insect of the Week will feature insect crop pests and their doppelgangers.

Is that a midge or a parasitoid? Why does it matter?

Small insects (i.e., less than 5 mm) are difficult to identify, even for trained specialists and professional entomologists. Especially if they are alive, flying around. Or in a sweep net sample quickly assessed in the field. In the case of midge and small-bodied parasitoids, they can be easily mistaken for one another, but their roles in agriculture tend to be very different. 

Some of the most well-known prairie midge species are agricultural pests, such as the orange coloured wheat midge (Sitodiplosis mosellana), black-coloured Hessian fly (Mayetiola destructor), and alfalfa blotch leafminer (Agromyza frontella). Other midge species found on the prairies include biting midge like no-see-ums (Ceratopogonidae), black flies (Simuliidae), and non-biting midge (Chironomidae). Midge that are not considered agricultural pests may provide some ecosystem services (i.e., pollination), while other midge are disease vectors and are pests of medical and veterinary concern. 

A – Hessian fly – adult
Scott Bauer, USDA Agricultural Research Service, Bugwood.org
B – Swede midge – adult
Susan Ellis, USDA APHIS PPQ, Bugwood.org
C – Wheat midge – adult
Mike Dolinski, MikeDolinski@hotmail.com

Parasitoids are natural enemies of other insects. Thus, many parasitoids are important because they help control agricultural pest populations. Adult parasitoids lay eggs, usually singly, onto or into their host. The larvae that hatch from the eggs develop using the host as food, and eventually kill the host. An individual host usually provides enough food for just one parasitoid larva. For this reason, parasitoids species are rarely larger in size than their host species. On the prairies, important parasitoid families that may be mistaken for midge or other small, black insects include: Aphidiinae, Braconidae, Chalchididae, Encyrtidae, Eulophidae, Platygasteridae, Pteromalidae and Trichogrammididae. Sticky cards or sweep net samples may contain hundreds or thousands of small, black, winged insects. Many are probably parasitoids and not pests so look closely when scouting. A few key differences to watch out for include:

  • Parasitoids have two pairs of wings while midge have only one pair of wings     
  • Parasitoids are often shiny or metallic shades of black, blue, purple or green     
  • Midge may look hairy; parasitoids rarely look hairy.  
1 – Aphidiinae – adult (Aphidius avenaphis)
Tyler Wist, AAFC
2 – Braconid wasp – adult
Alberta Agriculture and Rural Development
3 – Chalcid wasp – adult (Phasgonophora sulcata)
Michael Gates, Encyclopedia of Live, EOL.org
4 – Tetrastichus julis – adult parasitizing a cereal leaf beetle larva
Swaroop Kher, University of Alberta/AAFC
5 – Ichneumonid – adult (Banchus flavescens)
John Gavloski, Manitoba Agriculture, Food and Rural Development
6 – Platygasterid – adult (Inostemma sp.)
Tyler Wist, AAFC
7 – Pteromalid – adult (Pteromalus puparum)
Koorosh McCormack, Natural History Museum: Hymenoptera Section, EOL.org
8 – Trichogrammid – adult (Trichogramma sp.) parasitizing an egg  
Jack Kelly Clark, University of California Statewide IPM Program

Specific information on these families of parasitoids and on the species of midge listed here can be found in updated Field Crop and Forage Pests and their Natural enemies in Western Canada field guide.

Review previously featured insects by visiting the Insect of the Week page.

Post contributed by Dr. Meghan Vankosky.

Wind Trajectories

Agriculture and Agri-Food Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990’s.

In a continuing effort to produce timely information, the wind trajectory reports are available in two forms:

Prairie Crop Disease Monitoring Network

The Prairie Crop Disease Monitoring Network (PCDMN) represents the combined effort of our prairie pathologists who work together to support in-field disease management in field crops.  

In 2019, the PCDMN will release a series of weekly Cereal Rust Risk Reports throughout May and June.  Information related to trajectory events based on forecast and diagnostic wind fields and cereal rust risk is experimental, and is OFFERED TO THE PUBLIC FOR INFORMATIONAL PURPOSES ONLY. 

Background:  Agriculture and AgriFood Canada (AAFC) and Environment and Climate Change Canada (ECCC) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth. In addition, plant pathologists have shown that trajectories can assist with the prediction of plant disease infestations and are also beginning to utilize these same data. An introduction will be presented of efforts to identify wind trajectory events that may bring rust urediniospores into Western Canada from epidemic areas in the central and Pacific northwest (PNW) regions of the USA. Identification of potential events as well as an assessment of epidemic severity from source locations, and prairie weather conditions, will be used to assess the need for prompt targeted crop scouting for at-risk regions of the Canadian Prairies.

Two documents are available from the PCDMN:

Summary of wind trajectory and cereal rust risk assessment and the need for in-crop scouting in the Prairie region, June 18-24, 2019:

1. Pacific Northwest – Currently there is limited stripe rust development in the PNW, although there has been a moderate number of recent wind trajectories from the PNW.  Rainfall did occur in SK and some regions of Alberta.  Winter wheat is progressing into heading and beyond, and spring wheat is moving from the stem elongation stage to flag leaf emergence.  Thus, as of June 24, 2019, the risk of stripe rust appearance from the PNW is relatively low and scouting for this disease is not urgent.  

2. Texas-Oklahoma corridor – In general, crops are advancing towards maturity, while in many areas of Texas and Oklahoma crops have been harvested or are being harvested, and thus winter wheat crops in these areas are less of a source of rust inoculum.  There were no recent wind trajectories from this area, while rainfall did occur in SK and some regions of Alberta.  Winter wheat is progressing into heading and beyond, and spring wheat is moving from the stem elongation stage to flag leaf emergence.  Thus, as of June 24, 2019, the risk of leaf and stripe rust appearance from the Texas-Oklahoma corridor is low and scouting for these diseases is not urgent.  

3. Kansas-Nebraska corridor – Kansas crops are starting to mature with harvesting starting in some regions. In Nebraska, leaf and stripe rust development continues, and thus over the next few weeks this region could act as a significant source of rust inoculum for the Prairie region.  From June 18-24, 2019 there has been a low-moderate number of wind trajectories from this area.  Rainfall did occur in SK and some regions of Alberta, while winter wheat is progressing into heading and beyond, and spring wheat is moving from the stem elongation stage to flag leaf emergence.  Thus, as of June 24, 2019, the risk of leaf and stripe rust appearance from the Kansas-Nebraska corridor is relatively low and scouting for these diseases is not urgent.  Although further development of rust in Nebraska may increase the risk, the crop will soon start to progress towards maturity and will become less of a source of the cereal rusts.  It should be noted that rust symptoms have been observed in research plots in St. Paul, MN (Cereal Rust Survey, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, Dr. O. Fajolu, USDA-ARS Cereal Disease Lab, June 18, 2019).  Stripe and leaf rust have also been observed in research plots at the South Dakota State University Research Farm, while no rust was observed in commercial fields in southeastern and southcentral regions of the SD (Cereal Rust Survey, CEREAL-RUST-SURVEY@LISTS.UMN.EDU, Dr. E. Byamukama, South Dakota State University, June 18, 2019).

4. Currently, we are not aware of reports of stripe or leaf rust in commercial fields of winter or spring wheat across the Prairie region.

5.  Access the full downloadable report.

Corrections and updates to Weekly Update

Hello – This week three weather maps were incorrectly posted and the Saskatchewan bertha armyworm map was updated.  These items are now available for viewing:

Weather synopsis (Wk 12 for Jul 26th)

2018 Cumulative pheromone trap interceptions for Saskatchewan (as of July 18th)

Access the complete Weekly Update either as a series of Posts for Week 12 (July 26, 2018) OR a downloadable PDF version.  Also review the “Insect of the Week” for Week 12!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Meghan Vankosky or Jennifer Otani.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Subscribe to the Blog by following these three steps!

Insect of the Week – Natural enemies of the canola flower midge

This week’s Insects of the Week are two parasitoid wasps, an Inostemma sp. (Hymenoptera: Platygastridae) and a Gastrancistus sp. (Hymenoptera: Pteromalidae). These parasitoids are natural enemies of the canola flower midge (Contarinia brassicola, Diptera: Cecidomyiidae), a newly discovered fly species that uses canola as its host plant. The parasitoids have been found throughout the Prairies emerging from infested galls created by the canola flower midge. Little is known about these two species, but parasitism rates as high as 30% have been noted in northeast Saskatchewan.

Gastrancistrus sp. (Hymenoptera: Pteromalidae)
(c) 2016 Boyd Mori, AAFC
Inostemma sp. (Hymenoptera: Platygastridae)
(c) 2016 Boyd Mori, AAFC

Submitted by Dr. Boyd Mori and Dr. Meghan Vankosky

Find out more about the natural enemies of the canola flower midge and more at the Insect of the Week page!

Weekly Update

Greetings!

In-field scouting remains critical as we move into August!  Access the complete Weekly Update either as a series of Posts for Week 12 (July 26, 2018) OR a downloadable PDF version.  Also review the “Insect of the Week” for Week 12!

Questions or problems accessing the contents of this Weekly Update?  Please e-mail either Dr. Meghan Vankosky or Jennifer Otani.  Past “Weekly Updates” can be accessed on our Weekly Update page.

Subscribe to the Blog by following these three steps!

Weather synopsis

Weather synopsis – This past week (July 16 – 23, 2018) the average temperature (16.3 °C) was marginally warmer than long term average values (Fig. 1). The warmest weekly temperatures occurred across east-central AB and west-central/southern SK. The 30-day (June 23 – July 23) average temperature (15.8 °C) was similar to the long term average.  

Figure 1. Weekly (July 16-23, 2018) average temperature (°C).

Weekly and 30-day total precipitation was above average (Figs. 2 and 3).  The wettest region (30 day cumulative precipitation) was across eastern areas in SK and southern MB while central SK and most of AB continue to be dry.

Figure 2. Weekly (July 16 – 23, 2018) cumulative precipitation (mm).
Figure 3.  The 30-day (June 23 – July 23, 2018) cumulative precipitation (mm).

The map below reflects the Highest Temperatures occurring over the past 7 days (July 17-23, 2018) across the prairies and is available from Agriculture and Agri-Food Canada (Fig. 4). 

Figure 4. Highest temperature across the Canadian prairies the past seven days (July 17-23, 2018). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (24Jul2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

The map below reflects the Highest Temperatures occurring over the past 7 days (July 17-23, 2018) across the prairies and is available from Agriculture and Agri-Food Canada (Fig. 5). 

Figure 5. Lowest temperature across the Canadian prairies the past seven days (July 17-23, 2018). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (24Jul2018).  Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1529635048320).

The growing degree day map (GDD) (Base 10ºC, March 1 – July 22, 2018) is below:

The growing degree day map (GDD) (Base 5ºC, March 1 – July 22, 2018) is below:

The maps above are all produced by Agriculture and Agri-Food Canada.  Growers may wish to bookmark the AAFC Drought Watch Maps for the growing season.

Predicted grasshopper development

Grasshopper Simulation Model Output – The grasshopper simulation model will be used to monitor grasshopper development across the prairies. Weekly temperature data collected across the prairies is incorporated into the simulation model which calculates estimates of grasshopper development stages based on biological parameters for Melanoplus sanguinipes (Migratory grasshopper).  

As of July 23, 2018, most grasshopper populations are predicted to be primarily in the fifth instar or adult stages (Fig. 1A). Development is well ahead of average population development (Fig. 1B). Normally the first appearance of adults occurs during the last week of July (central Saskatchewan).  

Figure 1. Grasshopper development (average instar) based on model simulations for the current growing season (A) and for long term normal climate (B) (April 1 – July 23, 2018).

Grasshopper development varied across the prairies, and was predicted to be more advanced across the southern prairies (e.g., Lethbridge; Fig. 2A) than in the Peace River region (fourth and fifth instar stages; Fig. 2). 

Figure 2. Predicted grasshopper phenology at Lethbridge and Grande Prairie.
Values are based on model simulations, for April 1 – July 23, 2018.
Figure 3.  Clearwinged grasshopper stages including egg, first to fifth instar stages and adult (left to right).

Grasshopper Scouting Steps: 

● Measure off a distance of 50 m on the level road surface and mark both starting and finishing points using markers or specific posts on the field margin.

● Starting at one end in either the field or the roadside and walk toward the other end of the 50 m making some disturbance with your feet to encourage any grasshoppers to jump. 

● Grasshoppers that jump/fly through the field of view within a one meter width in front of the observer are counted. 

● A meter stick can be carried as a visual tool to give perspective for a one meter width.  However, after a few stops one can often visualize the necessary width and a meter stick may not be required. Also, a hand-held counter can be useful in counting while the observer counts off the required distance. 

● At the end point the total number of grasshoppers is divided by 50 to give an average per meter. For 100 m, repeat this procedure. 

● Compare counts to the following damage levels associated with pest species of grasshoppers:

0-2  per m² – None to very light damage
2-4  per m² – Very light damage
4-8  per m² – Light damage
8-12 per m² – Action threshold in cereals and canola
12-24 per m² – Severe damage 
>24 per m² – Very severe damage

* For lentils at flowering and pod stages, >2 per m² will cause yield loss.
* For flax at boll stages, >2 per m² will cause yield loss.

Biological and monitoring information related to grasshoppers in field crops is posted by Manitoba Agriculture, Saskatchewan Agriculture, Alberta Agriculture and Forestry, the BC Ministry of Agriculture and the Prairie Pest Monitoring Network.  Also refer to the grasshopper pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” as an English-enhanced or French-enhanced version.

Wheat midge

Wheat Midge (Sitodiplosis mosellana) – Warm, moist conditions in Manitoba are predicted to be favourable for development wheat midge larvae (Fig. 1A). In Manitoba and eastern Saskatchewan larvae should be dropping into the soil (Fig. 1B). 

Figure 1. Percent wheat midge in the early larval stage (A) and larval cocoons (B) based on model simulations for April 1 – July 23, 2018.

Model runs for Saskatoon indicate the midge development, due to dryer conditions in June, is slower than predicted emergence at Brandon and Edmonton (Fig. 2). 

Figure 2. Predicted wheat midge phenology at Brandon, Saskatoon and Edmonton.
Values are based on model simulations, for April 1 – July 16, 2018.

Monitoring:

When monitoring wheat fields, pay attention to the synchrony between flying midge and anthesis.  

In-field monitoring for wheat midge should be carried out in the evening (preferably after 8:30 pm or later) when the female midges are most active. On warm (at least 15ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (photographed by AAFC-Beav-S. Dufton & A. Jorgensen below). Midge populations can be estimated by counting the number of adults present on 4 or 5 wheat heads. Inspect the field daily in at least 3 or 4 locations during the evening.

REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (photographed by AAFC-Beav-S. Dufton below), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember your insecticide control options for wheat midge also kill these beneficial insects which help reduce midge populations.

Economic Thresholds for Wheat Midge:

a) To maintain optimum grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.

b) For yield only: 1 adult midge per 4 to 5 heads. At this level of infestation, wheat yields will be reduced by approximately 15% if the midge is not controlled.

Inspect the developing kernels for the presence of larvae and the larval damage. 

Click here to review the 2018 wheat midge forecast map.  

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  A review of wheat midge on the Canadian prairies was published by Elliott, Olfert, and Hartley in 2011.  Additionally, more information can be found by accessing the pages from the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Field Guide”.  View ONLY the Wheat midge pages but remember the guide is available as a free downloadable document as both an English-enhanced or French-enhanced version.

Lygus in canola

Lygus bugs (Lygus spp.) – The economic threshold for Lygus in canola is applied at late flower and early pod stages.  

Adult L. lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
Fifth instar lygus bug nymph (3-4 mm long) (photo:  AAFC-Saskatoon).

Damage: Lygus bugs have piercing-sucking mouthparts and physically damage the plant by puncturing the tissue and sucking plant juices. The plants also react to the toxic saliva that the insects inject when they feed. Lygus bug infestations can cause alfalfa to have short stem internodes, excessive branching, and small, distorted leaves. They feed on buds and blossoms and cause them to drop. They also puncture seed pods and feed on the developing seeds causing them to turn brown and shrivel.

Scouting tips to keep in mind:

Begin monitoring canola when it bolts and continue until seeds within the pods are firm. Since adults can move into canola from alfalfa, check lygus bug numbers in canola when nearby alfalfa crops are cut.

Sample the crop for lygus bugs on a sunny day when the temperature is above 20°C and the crop canopy is dry. With a standard insect net (38 cm diameter), take ten 180° sweeps. Count the number of lygus bugs in the net.

Sampling becomes more representative IF repeated at multiple spots within a field.  For lygus bug monitoring, sampling is most accurate when repeated at a total of 15 spots within the field.  Samples can be taken along or near the field margins. Calculate the cumulative total number of lygus bugs and then consult the sequential sampling chart (Figure C). 

If the total number is below the lower threshold line, no treatment is needed. If the total is below the upper threshold line, take more samples. If the total is on or above the upper threshold line, calculate the average number of lygus bugs per 10-sweep sample and consult the economic threshold table.

Sequential sampling for lygus bugs at late flowering stage in canola.

The economic threshold for lygus bugs in canola covers the end of the flowering (Table 1) and the early pod ripening stages (Table 2). Once the seeds have ripened to yellow or brown, the cost of controlling lygus bugs may exceed the damage they will cause prior to harvest, so insecticide application is not warranted.

Consider the estimated cost of spraying and expected return prior to making a decision to treat a crop. 

Remember that insecticide applications at bud stage in canola have not been proven to result in an economic benefit in production.  The exception to this is in the Peace River region where early, dry springs and unusually high densities of lygus bug adults can occasionally occur at bud stage.  In this situation, high numbers of lygus bugs feeding on moisture-stressed canola at bud stage is suspected to result in delay of flowering so producers in that region must monitor in fields that fail to flower as expected.

Table 1.  Economic thresholds for lygus bugs in canola at late flowering and early pod stages (Wise and Lamb 1998).

1 Canola crop stage estimated using Harper and Berkenkamp 1975).
2 Economic thresholds are based on an assumed loss of 0.1235 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).

Table 2.  Economic thresholds for lygus bugs in canola at pod stage (Wise and Lamb 1998).

 3 Economic thresholds are based on an assumed loss of 0.0882 bu/ac per lygus bug caught in 10 sweeps (Wise and Lamb. 1998. The Canadian Entomologist. 130: 825-836).

Biological and monitoring information related to Lygus in field crops is posted by the provinces of Manitoba or Alberta fact sheets or the Prairie Pest Monitoring Network’s monitoring protocol.  Also refer to the Lygus pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.

Bertha armyworm

Bertha armyworm (Lepidoptera: Mamestra configurata) – Pheromone trapping across the prairies is almost complete for the 2018 growing season but now it is important to scout for larvae feeding on leaves and developing pods.

Monitoring:

  • Larval sampling should commence once the adult moths are noted. 
  • Sample at least three locations, a minimum of 50 m apart. 
  • At each location, mark an area of 1 m2 and beat the plants growing within that area to dislodge the larvae. 
  • Count them and compare the average against the values in the economic threshold table below:  

Scouting tips:

  • Some bertha armyworm larvae remain green or pale brown throughout their larval life. 
  • Large larvae may drop off the plants and curl up when disturbed, a defensive behavior typical of cutworms and armyworms. 
  • Young larvae chew irregular holes in leaves, but normally cause little damage. The fifth and sixth instar stages cause the most damage by defoliation and seed pod consumption. Crop losses due to pod feeding will be most severe if there are few leaves. 
  • Larvae eat the outer green layer of the stems and pods exposing the white tissue. 
  • At maturity, in late summer or early fall, larvae burrow into the ground and form pupae.

Albertans can access the online reporting map (screenshot below retrieved 24Jul2018 for reference):

Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 26Jul2018 for reference):

Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates.  The July 25th update summarized that, “out of the 99 traps, 87 currently have cumulative counts in the low risk category (less than 300), one trap is in the moderate risk range, and 11 traps are in the uncertain risk category.  Most of the highest cumulative counts so far are in the western part of Manitoba.”

Biological and monitoring information related to bertha armyworm in field crops is posted by the provinces of Manitoba, Saskatchewan, Alberta and the Prairie Pest Monitoring Network.  Also refer to the bertha armyworm pages within the new “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” – both English-enhanced or French-enhanced versions are available.

Cabbage seedpod weevil

Cabbage seedpod weevil (Ceutorhynchus obstrictus) –  There is one generation of CSPW per year and the overwintering stage is the adult which is an ash-grey weevil measuring 3-4mm long (Refer to lower left photo).  Adults typically overwinter in soil beneath leaf litter within shelter belts and roadside ditches.

Monitoring:  

  • Begin sampling when the crop first enters the bud stage and continue through the flowering. 
  • Sweep-net samples should be taken at ten locations within the field with ten 180° sweeps per location.  
  • Count the number of weevils at each location. Samples should be taken in the field perimeter as well as throughout the field.  
  • Adults will invade fields from the margins and if infestations are high in the borders, application of an insecticide to the field margins may be effective in reducing the population to levels below which economic injury will occur.  
  • An insecticide application is recommended when three to four weevils per sweep are collected and has been shown to be the most effective when canola is in the 10 to 20% bloom stage (2-4 days after flowering starts). 
  • Consider making insecticide applications late in the day to reduce the impact on pollinators.  Whenever possible, provide advanced warning of intended insecticide applications to commercial beekeepers operating in the vicinity to help protect foraging pollinators.  
  • High numbers of adults in the fall may indicate the potential for economic infestations the following spring.

Damage: Adult feeding damage to buds is more evident in dry years when canola is unable to compensate for bud loss.  Adults mate following a pollen meal then the female will deposit a single egg through the wall of a developing pod or adjacent to a developing seed within the pod (refer to lower right photo).  Eggs are oval and an opaque white, each measuring ~1mm long.  Typically a single egg is laid per pod although, when CSPW densities are high, two or more eggs may be laid per pod.

There are four larval instar stages of the CSPW and each stage is white and grub-like in appearance ranging up to 5-6mm in length (refer to lower left photo).  The first instar larva feeds on the cuticle on the outside of the pod while the second instar larva bores into the pod, feeding on the developing seeds.  A single larva consumes about 5 canola seeds.  The mature larva chews a small, circular exit hole from which it drops to the soil surface and pupation takes place in the soil within an earthen cell.  Approximately 10 days later, the new adult emerges to feed on maturing canola pods.  Later in the season these new adults migrate to overwintering sites beyond the field.

Albertan growers can report and check the online map for CSPW posted by Alberta Agriculture and Forestry (screenshot provided below for reference; retrieved 24Jul2018).

Please find additional detailed information for CSPW in fact sheets posted by Alberta Agriculture and Forestry, Saskatchewan Agriculture, or the Prairie Pest Monitoring Network.

Cereal Aphid Manager (CAM)

Reminder – Aphids can cause significant damage to fields and increase crop losses, but just because aphids are present in a grain field doesn’t mean they will have a negative economic impact on production. This is especially true if there are aphid’s natural enemies (beneficial insects) in the field to keep them under control.

The Cereal Aphid Manager is an easy-to-use mobile app that helps farmers and crop advisors control aphid populations in wheat, barley, oat or rye. It is based on Dr. Tyler Wist’s (AAFC-Saskatoon) innovative Dynamic Action Threshold model. The model treats the grain field as an ecosystem and takes into account many complex biological interactions including:

  • the number of aphids observed and how quickly they reproduce
  • the number of different natural enemies of aphids in the field and how many aphids they eat or parasitize per day
  • the lifecycles of aphids and their enemies taking into account developmental stages, egg laying behaviour, population growth rate, lifespan, etc.

By taking into consideration factors like these, the app predicts what the aphid population will be in seven days and the best time to apply insecticide based on economic thresholds.

Available in iOS and Android.

To learn more and to download, go to AAFC’s CAM webpage.

Note: Cereal aphids can blow up from the South at any time which cannot be predicted by the app. Therefore, farmers and crop advisors should regularly check fields during the growing season regardless of what Cereal Aphid Manager Mobile may recommend.

CAM Homepage
CAM monitoring report and recommendation
CAM icon

West Nile Virus and Culex tarsalis

West Nile Virus Risk –  The regions most advanced in degree-day accumulations for Culex tarsalis, the vector for West Nile Virus, are shown in the map below.  Areas highlighted yellow then orange are approaching sufficient heat accumulation for mosquitoes to emerge while mosquitoes will be flying in areas in red so wear DEET to stay protected! 

Health Canada posts information related to West Nile Virus in Canada.  Health Canada also tracks WNV through human, mosquito, bird and horse surveillance.  Link here to access the most current weekly update (July 7, 2018) on 2018 testing (screenshot retrieved 25Jul2018 provided below for reference only).

Reminder – The 2017 WNV surveillance map for human cases is available here but a screenshot is posted below for reference.

Figure 1.  As of surveillance week 49, ending December 9, 2017, the preliminary data indicated 197 human cases of WNV in Canada; twenty-five from Québec, 159 from Ontario, five from Manitoba, seven from Alberta, and one from British Columbia.

The Canadian Wildlife Health Cooperative compiles and posts information related to their disease surveillance for West Nile Virus in birds.  As of June 28, 2018, 642 birds were examined and zero have tested positive for West Nile virus. 

Provincial Insect Pest Reports

Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information: 

Manitoba‘s Insect and Disease Updates for 2018 can be accessed here. Issue #9 (posted for July 25, 2018) includes a summary of cumulative bertha armyworm counts from pheromone traps for 2018 and importance of monitoring in canola (bertha armyworm and diamondback moth) and soybeans (spider mites) but an overall low level of insect concerns so far.

Saskatchewan‘s Crop Production News for 2018 is posted with Issue #5 now available. This issue includes a description of cereal leaf beetle in Saskatchewan. Growers can review articles on how to scout for cutworms, how to assess plant stand densities in flax or canola, and for flea beetles, pea leaf weevils. Also note the following diamondback moth pheromone trap interception counts from across the regions (updated June 27, 2018):

Alberta Agriculture and Forestry’s Call of the Land regularly includes insect pest updates from Scott Meers. The most recent Call of the Land (posted July 19, 2018) identified that SOME bertha armyworm pheromone traps over a wide geographic range have started to intercept higher numbers of moths. Elevated trap counts require further in-field scouting to accurately detect the number and staging of bertha armyworm larvae that will now feed on developing canola pods. Pea leaf weevil is a pest of several legume species so growers trying to establish seedling alfalfa in areas where pea leaf weevil has been confirmed are advised to scout. Early trends from the early flower canola survey include relatively lower numbers of cabbage seedpod weevil, lygus bugs, diamondback moth and leafhopper numbers compared to recent years but the prevalence of beneficial arthropods in some fields.

Crop reports

Crop reports are produced by:

The following crop reports are also available: