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.
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 Wk15 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.
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)
Access the Provincial Insect Pest Report for Wk15 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).
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.
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 Wk15 for updates for this economic insect pest.
Access the Provincial Insect Pest Report for Wk15 for updates for this economic pest.
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.
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 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 Wk15 for updates for this economic insect pest.
Two species of crickets of agricultural significance can be found in more southern regions of the Canadian prairies. The Mormon cricket (Anabrus simplex Haldeman) is typically active as an adult from late June to mid-September. Host plants for the nymphs and adults include broad-leafed plants but they will also feed on sagebrush, grasses and small shrubs, as well as wheat, barley, alfalfa, sweet clover, some forages and garden vegetables plus other insects. Fall field crickets (Gryllus pennsylvanicus Burmeister) are normally observed from late July to the end of September. Fall field crickets (nymphs and adults) can feed and affect seed yields in forages grown for seed, cereals, and some small fruits when they occur at high densities, however, fall field cricket adults are predators of grasshopper eggs.
Biological and monitoring information for fall field cricket (Gryllus pennsylvanicus Burmeister) and Mormon cricket (Anabrus simplex Haldeman) are described in the cricket 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.
While the PPMN no longer predicts the development of Culex tarsalis, the dominant vector for West Nile Virus(WNV), areas of the Canadian prairies in 2024 have received high levels of precipitation. This is noteworthy because the larvae of C. tarsalis can develop in, “agricultural tailwater, alkaline lake beds, fresh and saline wetlands, secondary treated sewage effluent and oil field run-off” (Centre for Vector Biology URL retrieved 2024Jul04).
Culex tarsalis have a base developmental threshold of 14.3 °C. Across the Canadian prairies, WNV transmission is of greatest concern as the second generation of C. tarsalis females begin to fly (by 250-300 degree days). In fact, an additional 109 degree days (using Base 14.3 °C) is required within a given mosquito population for virus development to complete to the point that transmission might occur.
Historically, by mid-July, C. tarsalis adults begin to fly in southern parts of the Canadian prairies. By August, protect yourself from mosquitoes when outdoors – this is the window when mosquitoes are most numerous plus have the greatest chance of carrying WNV. Field scouts and outdoor enthusiasts should wear DEET to protect against C. tarsalis and WNV.
For reference, the following table of data was quickly generated using AAFC Drought Watch Historical Daily Air Temperatures since April 1, 2024:
Location
Degree Days (base 14.3 °C) as of August 13, 2024
Observed date heat units >200 Degree Days
Potential date when >200 Degree Days attained
Potential date when >390 Degree Days attained
Winnipeg
330.6
July 20
—
August 28
Saskatoon
266.2
July 29
—
Unable to project
Lethbridge
294.7
July 25
—
Unable to project
Edmonton
188.6
—
August 18
Unable to project
Grande Prairie
220.9
August 11
—
Unable to project
Note: Potential dates calculated using daily mean of 18°C until August 30, 2024, then daily mean of 15°C for September 1-30, 2024.
As harvest approaches, remember 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.
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’SCrop Pest Updates for 2024 are available. Access the August 15, 2024 report (or access the PDF copy). Bookmark the insect pest homepage to access fact sheets and more! Highlights reported by Dr. J. Gavloski include: • Bertha armyworm – “Continues to be noticed at high levels in some canola fields in the Southwest region and western part of the Central region. Access Manitoba’s fact sheet for this insect to support in-field scouting for larvae now. • Lygus bugs – “High levels were noted in some canola fields in the Northwest and Easter regions”. Review the report for scouting tips and photos of lygus bug adults and nymphs. • Aphids – “Soybean aphids have been increasing in some areas but no reports yet of economic levels or insecticide applications” being applied so far. • Green caterpillars in canola – Review the report for tips and photos to differentiate a number of species that can be present now in canola. • Grasshoppers – The annual grasshopper survey is underway now. Interested participants can find the protocol, data sheet, and steps to submit data in the newly updated protocol. • Reminder – Insects in Stored Grain – AAFC in Winnipeg is seeking producer participation for grain bin monitoring in September-October 2024. Learn more here and find out how to participate.
ALBERTA’SInsect 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., diamondback moth and bertha armyworm (August 6, 2024); aphids in field crops, canola flower midge scouting (July 29, 2024); 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 (as of August 1, 2024). • Cabbage seedpod weevil monitoring – Sweep-net count data can be reported here then the data populates the Live Map (as of August 8, 2024). • Diamondback moth monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map (as of July 4, 2024). Remember to scout fields for larvae. • Bertha armyworm pheromone trap monitoring – Cumulative counts arising from weekly data are available so refer to the Live Map (as of August 8, 2024). Remember to scout fields for larvae.
Insect scouting season continues, even though harvest has already started in some regions! Development of many pest insects has been ahead of schedule all year in most parts of the prairies, thanks to warmer than average weather during this growing season.
Adult grasshoppers are now in flight and will be laying eggs across the prairie region. Scouting individual fields is the best way to estimate crop risk. At this time of year, we start to look forward to next season. Insect surveyors are working to estimate grasshopper populations in ditches/roadsides and may be collecting samples of adult grasshoppers for species identification.
Aside from grasshoppers, fall surveys for wheat midge and wheat stem sawfly will begin as harvest is completed in Alberta and Saskatchewan. This week, the Insect of the Week post features wheat stem sawfly, including information about how to estimate their population densities in the fall.
Diamondback moth, if present, are into the fourth non-migrant generation across most of the prairies now and could be starting a fifth generation in some southern parts of the prairies. Keep in mind that diamondback moth develop quickly in warm weather which could lead to rapidly increasing populations over the summer.
On the topic of diamondback moths, Dr. Maya Evenden’s lab at the University of Alberta is conducting research on diamondback moth, flea beetles, and alfalfa weevil. Learn more about Maya’s research program in this week’s Prairie Research post.
Use the links in the Provincial Insect Updates post to learn more about what is happening with populations of insect pests (and beneficial insects) in your province.
Remember:
1) There are many resources available to help with planning for late-season insecticide applications to ensure Pre-Harvest Interval requirements are met.
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.
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.
The Parkland region of Alberta, Manitoba, and Saskatchewan experienced cooler temperatures and rain in the past week, but warm, dry conditions continue to persist across most of the southern prairies.This past week (August 7-13, 2023), the prairie average daily temperature was slightly cooler than the long-term average. The coolest temperatures occurred across the central and eastern areas of the Parkland region (Fig 1). In comparison to the Parkland region, temperatures were much warmer across southern Alberta and southwest Saskatchewan.
Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of August 7 to 13, 2023.
Precipitation for the period of August 7-13, 2023 was highest for a large region northeast of Edmonton in Alberta, east of Saskatoon and north of Regina in Saskatchewan, and in most of Manitoba (Fig. 2). Southern Alberta has been extremely dry all of summer 2023 and that trend continued in the last week (Fig. 2). Similarly, it has continued to be dry in southwestern Saskatchewan.
Figure 2. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 7-13, 2023.
This year, we used scatterplots for growing season average temperature and total rainfall to provide relative comparisons of site specific growing conditions across the prairies. Growing season temperature and precipitation has varied significantly across the prairies in 2023. Lethbridge has had less than 100 mm of rain, for example, while Grande Prairie has reported 250 mm. Growing season average temperatures have ranged from 12.3°C to 15.4°C. Northwestern Alberta locations are categorized as relatively cool and wet in 2023 (Fig. 5). In contrast, most locations in the southern prairies can be characterized as warm and dry.
Figure 3. Site-specific comparison of growing season average temperature (°C) and cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 – August 13, 2023. The red line indicates the average temperature and the blue line represents the average rainfall.
After arriving in western Canada in the spring, migrant diamondback moths begin to reproduce. In western Canada, there are usually up to four non-migrant generations of diamondback moth produced in ‘local populations’ during the growing season.
Due to warm weather in 2023, development of diamondback moth populations is well ahead of average development. Model simulations to August 13, 2023, indicate that the fourth generation of non-migrant adults (based on early May arrival dates) are currently occurring across the Canadian prairies (Fig. 1) and that fifth generation non-migrant adults could also be occurring in some localized areas of the southern prairies.
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 13, 2023.
In a ‘normal year’ based on climate normals data (e.g., 30-year averages), we would expect only the third generation of non-migrant diamondback moth to be occurring across the northern prairie region at this time of year, with the fourth generation occurring across the extreme southern region of the prairies (Fig. 2).
Figure 2. The predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of August 13, based on climate normals data.
Considering advanced canola development, risk across the southern and central regions of the prairies associated with the development of a fifth generation of diamondback moth should be minimal. However, in regions where broccoli, rutabaga, and other brassica vegetables are grown and where crops are late to mature, these crops could still be at risk. Keep scouting for diamondback moth where crops are still green and could provide a desirable food source for developing diamondback moth larvae.
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.
*Text for this post prepared by Priyatha Sundaran, Sharavari Kulkarni and Maya Evenden, from the University of Alberta.
Dr. Maya Evenden’s lab in the Department of Biological Sciences at the University of Alberta researches insect behaviour, chemical ecology and integrated pest management. They study how insects orient and maneuver in their environment and exploit that knowledge for the development of IPM tactics. This summer the Evenden lab has multiple agriculture-based projects targeting diamondback moth, flea beetles, pea leaf weevil and alfalfa weevil. Here we highlight the work of an MSc student, Priyatha Sundaran, and a postdoctoral fellow, Dr. Sharavari Kulkarni.
Priyatha’s research focuses on the presence and distribution of alfalfa weevil (Hyperapostica), in alfalfa grown for seed in southern Alberta. The study also assesses the diversity of Sitona spp. in sampled alfalfa fields. In three field seasons, alfalfa weevils have been sampled with soil and sweep samples, and emergence and pit fall traps. Soil samples at the beginning and end of each crop season estimate the density of alfalfa weevils in the soil over the winter. Sweep net samples can collect both larvae and adults to monitor alfalfa weevil density in the field for timely use of insecticides. Pitfall trap capture can indicate weevil movement in and out of the field over the course of the growing season. Emergence cages assessed the overwintering locations of weevils inside and outside the field. Initial results reinforce the effectiveness of sweep net sampling to monitor alfalfa weevil populations with peak larval activity in June-July. Alfalfa weevils were captured in equal numbers in pitfall traps placed at the edge and in the interior of the field suggesting that alfalfa weevils remain within alfalfa fields, unlike in other parts of their range. Sitona spp. bycatch consisted mostly of alfalfa curculio (Sitona lineellus) and pea leaf weevil (Sitona lineatus).
Alfalfa weevil sampling methods used in alfalfa fields grown for seed: A) Emergence cages were located inside and outside the field to reveal the overwintering sites of alfalfa weevils. B) Two hundred sweep samples were collected from four locations in each field throughout the growing season in three seasons. C) Directional pitfall traps were employed in the 2023 season to measure the direction of movement of alfalfa weevils in the field. Pictures by Priyatha Sundaran, University of Alberta.
Sharavari’s research focuses on developing weather-based stage-structured predictive models for two important canola pests, striped flea beetles, (Phyllotreta striolata (Fab.)) and crucifer flea beetles (Phyllotreta cruciferae (Goeze)). Flea beetles are oligophagous species feeding mainly on canola (Brassica napus L. and Brassica rapa L.) and mustard (Brassica juncea L.). Sharavari used field surveys to assess local phenology and laboratory bioassays to study the effect of temperature on beetle development and interspecific competition between the two species. The flea beetle surveys were conducted in the spring (pre-seeding) and fall of 2021, 2022 and 2023 across 20+ canola fields throughout Alberta. Season-long, site-specific weather data was collected for modeling and validation. None of the available monitoring methods provides accurate forecasting for flea beetles, and weather-based phenology models can help producers make informed decisions on timing and the need to apply foliar insecticides for flea beetle management. Lab assays showed a dramatic effect of temperature on the time and success of egg hatch and development time from egg to adult. On-going lab work is testing for plant-mediated interactions between the two species to understand if P. cruciferae prefers to feed and oviposit on plants previously damaged by P. striolata and to determine if inter-species interactions have fitness costs.
Flea beetle monitoring in commercial canola fields with yellow sticky cards at sites with weather stations for site-specific temperature measurements. Pictures by Sharavari Kulkarni, University of Alberta.
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! Issue 4 is available now, as well as a Crop Report covering the period of August 1 to August 7. The crop report notes that grasshoppers and flea beetles are causing some late season damage to crops. 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). The August 16 issue provides an update on Lygus bugs, diamondback moth, flea beetles, grasshoppers and aphids. It also has great pictures to help identify insect pests!
As harvest gets started, 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.
Native to North America, the wheat stem sawfly is an economic pest depending on spring and durum wheat as its main crop hosts. These insects also target winter wheat, rye, grain corn and barley, in addition to feeding on native grass species. It is interesting to note that wheat stem sawflies do not feed on oat crops, as oats are toxic to wheat stem sawfly.
An adult wheat stem sawfly. Picture by Dylan Sjolie, AAFC-Saskatoon.
Wheat stem sawfly larvae feed on pith inside the stems of their host plant. Their feeding activity affects crop yield and quality. As infested host plants mature, the larvae travel down the stem to its base, where “V” shaped notches are cut into the stem a little above ground level. These notches leave plants vulnerable to collapsing or lodging, especially during wind events. Because wheat stem sawflies also breed and develop on native grass species, economic damage tends to be most prevalent around crop margins where native and agricultural plants are found close together.
An adult wheat stem sawfly. Picture by Dylan Sjolie, AAFC-Saskatoon.
Adult wheat stem sawflies are 8–13 mm long with a wasp-like resemblance, due to their black body and yellow legs. Females have an egg-laying organ (an ovipositor) that extends from their abdomen. When resting on plant stems, these insects will point their heads downward. Mature larvae are 13 mm long and resemble whitish worms with brown heads.
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.
TEMPERATURE: Average temperatures for the 2022 growing season continue to be similar to long-term average values. This past week (August 8-14, 2022), the average daily temperature for the prairies was 2 °C warmer than the previous week and 2.5 °C warmer than climate normals. The warmest temperatures were observed across southwestern Saskatchewan and the southern and central regions of Alberta (Fig. 1). The prairie-wide average 30-day temperature (July 16 – August 14, 2022) was 1.5 °C warmer than the long-term average 30-day temperature. Average temperatures have been warmest across southern Alberta and southwestern Saskatchewan (Fig. 2).
Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of August 8-14, 2022.Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of July 16 to August 14, 2022.
The average growing season (April 1-August 14, 2022) temperature for the prairies has been similar to observed climate normal values. The growing season has been coolest across the Peace River region (Fig. 3).
Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to August 14, 2022.
PRECIPITATION: The greatest weekly precipitation amounts occurred across eastern Saskatchewan last week (August 8-14, 2022) (Fig. 4). 30-day (July 16-August 14, 2022) rainfall amounts continue to be greatest across southeastern Manitoba while dry conditions persist across southern Alberta and southwestern Saskatchewan (Fig. 5).
Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 8-14, 2022.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (July 16 to August 14, 2022).
Growing season rainfall for the prairies (April 1 – August 14, 2022) has been near normal for Alberta and above normal in Manitoba. Total rainfall continues to be greatest across Manitoba and eastern Saskatchewan and least across central and south-central Saskatchewan (Fig. 6).
Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to August 14, 2022.
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.
Model simulations were used to estimate grasshopper development as of August 14, 2022. Potential risk continues to be greatest across central and southern regions of Saskatchewan and southeastern Alberta. Simulations indicate that prairie populations are in the adult stage and females are beginning to lay eggs in the soil. Earlier oviposition can result in above-average production of eggs and increased overwintering survival of eggs.
The oviposition index provides a method to assess where egg production is greatest; higher oviposition index values indicate where egg production is greatest. Model runs for the 2022 growing season (April 1 – August 14) predicted that ovipositon rates so far in 2022 have been greatest across southern Saskatchewan and southeastern Alberta (Fig. 1).
Figure 1. Grasshopper (Melanoplus sanguinipes) oviposition index across the Canadian prairies as of August 14, 2022 . Higher ovipositional index values indicate greater potential for oviposition.
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.
Recent warm conditions have resulted in the rapid development of diamondback moth populations. Model simulations to August 14, 2022, indicate that the fourth 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 in 2022 than expected based on 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 August 14, 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 August 14, based on climate normal data.
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 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).
Figure 4. Diamondback moth pupa within silken cocoon.
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.
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.
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 Keep 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 has 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.
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 August 14, 2022and where present, C. tarsalis development has progressed. Remember, areas highlighted yellow have accumulated sufficient heat units for the second generation of C. tarsalis to fly. Many areas of the prairies well exceed the 250-300 DD of base 14.3 °C (e.g., areas orange red any any shade of pink) represented in Figure 1. Outdoor enthusiasts falling within areas highlighted yellow, orange, red or pink should wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are at increased risk for WNV from late July but typically peaks over the long weekend in August.
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of August 14, 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 was approximately 12-15 days in areas highlighted mauve and approximately 22-24 days in areas highlighted light green.
Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of August 14, 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 July 30, 2022; retrieved August 18, 2022) and provided below.
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 18Aug2022).
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.
Provincial entomologists provide insect pest updates throughout the growing season so link to their information:
MANITOBA’SCrop Pest Updates for 2022 are up and running! Access a PDF copy of the August 17, 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! • Aphids in soybeans and small grains, Lygus bugs, grasshoppers, crickets, and diamondback moth were described in the August 17 issue.
ALBERTA’SInsect 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.
The rusty grain beetle (Cryptolestes ferrugineus) is the most common and serious pest of stored grain on farms and in elevators across the Canadian prairies. It makes up about 95 % of all grain insects detected by the Canadian Grain Commission in grain elevators across the country. Its very small size (1.5–2.5 mm long) allows it to easily crawl between grain kernels and quickly spread throughout stored grain. Its high fertility (up to 423 eggs per female) and fast development (about one generation per month) can result in serious losses if the grain is kept above 20 °C, or if it is kept too moist for too long, or if there is a hot spot or spoiled grain somewhere in the grain bin because this species thrives in spoiled grain. Additionally, the Canadian Grain Act prohibits the receipt and marketing of infested grain (i.e., grain containing any injurious, noxious or troublesome insect or animal pests). Elevators cannot accept grain if they detect this insect in it.
Rusty Grain Beetle on a kernel of wheat. Photo : Vincent Hervet, AAFC
The rusty grain beetle’s most favoured foods are: wheat, rye, corn, barley, and millet. It can also develop on a wide range of fungus species and moldy substrates. Interestingly, this beetle cannot penetrate undamaged seeds, so it requires a seed to be either spoiled, broken or cracked (a microscopic crack will suffice) in order to feed on it. Physical damage to grain is typically caused by harvesting and handling. The rusty grain beetle cannot develop below 20 °C so grain stored in dry conditions and maintained below 20 °C will be safe from infestation from this species. Keeping grain below 18 °C will ensure that it is safe from other insect species as well.
Effective ways to eliminate or reduce the risk of infestations include: • Thoroughly cleaning and sanitizing bins between uses; • Cleaning up grain residue from the surroundings to prevent the multiplication of grain insects near grain storage areas (spillages on the ground, residues left in combines or augers, etc.); • Ensuring bins are sealed tight to prevent moisture or snow from entering; • Reducing the temperature and moisture content of stored grain to safe levels as soon as possible after harvest (using these helpful Safe Storage Charts). • Also access the Canadian Grain Commission’s information on Grain Quality.
To learn more about current storage practices, storage issues, and to understand the main insect issues in stored grains across the Canadian prairies, Dr. Vincent Hervet with Agriculture and Agri-Food Canada (vincent.hervet@agr.gc.ca) is currently surveying insects in farm grain bins across the Prairie Provinces of Canada. Volunteer growers in Alberta, Saskatchewan, and Manitoba are needed to participate in this survey so we can better understand issues in farm-stored grain and how to address them.
HOW YOU CAN HELP: If you wish to participate in this survey, or if you wish to have more details about the survey, please contact Dr. Vincent Hervet (vincent.hervet@agr.gc.ca; 204-915-6918).
Week 15 and swathers and combines are now running across the prairies! Be sure to catch the Insect of the Week – it’s the mormon cricket!
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.
TEMPERATURE: This past week (August 2-8, 2021) the prairies continued to experience above-average temperatures and extremely dry conditions. The warmest temperatures were observed across southern and central regions of Alberta, Saskatchewan, and Manitoba (Fig. 1). Across the prairies, the average 30-day (July 10 – August 8, 2021) temperature was 2.5°C warmer than climate normal values (Fig. 2). The 2021 growing season (April 1 – August 8, 2021) has been 1.6 °C warmer than average (Fig. 3).
Figure 1. 7-day average temperature (°C) observed across the Canadian prairies for the period of August 2- 8, 2021.Figure 2. 30-day average temperature (°C) observed across the Canadian prairies for the period of July 10 – August 8, 2021.Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 – August 8, 2021.
Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-August 9, 2021) can be viewed by clicking the hyperlinks. Over the past 7 days (August 5-11, 2021), the lowest temperatures recorded across the Canadian prairies ranged from < 0 to >12 °C while the highest temperatures observed ranged from <22 to >34 °C. Check the number of days of >25 °C or >30 °C across the Canadian prairies (April 1-August 11, 2021). Access these maps and more using the AAFC Drought Watch webpage interface.
PRECIPITATION: Weekly (August 2-8, 2021) rainfall amounts were generally less than 5 mm (Fig. 4). Rainfall amounts for the period of July 10 – August 8 (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 below average across most of the prairies. A region extending from Regina to the USA border is the only region reporting near-normal rainfall for the period of April 1 – August 8, 2021. A region extending from Lethbridge to northeastern Saskatchewan has had less than 100 mm of rain (Fig. 6) in 2021.
Figure 4. 7-day cumulative rainfall (mm) observed across the Canadian prairies for the period of August 2 – 8, 2021.Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 10 – August 8, 2021Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 – August 8, 2021.
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.
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.
Diamondback moths (DBM; Plutella xylostella) are a migratory invasive species. The model, based on climate data, indicates most DBM populations should be in the third generation (Fig. 1). Model simulations to August 8, 2021, predict an additional generation for the current growing season PLUS a third and fourth generation of non-migrant adults are currently emerging across the Canadian prairies (Fig. 2).
Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to occur across the Canadian prairies as of August 8 (based on climate normals data).Figure 2. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to occur across the Canadian prairies as of August 8, 2021.
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).
Figure 4. Diamondback moth pupa within silken cocoon.
Model simulations were used to estimate grasshopper (Melanoplus sanguinipes) development as of August 8, 2021. Compared to average growing season temperatures, above-average temperatures during June, July, and early August continue to result in a noticeable increase in the rate of grasshopper development.
Oviposition generally begins in early August. Model simulations for 2021 predicted that oviposition was expected to begin in mid-July. Earlier oviposition can result in above-average production of eggs resulting in potential risk for the following growing season. Climate data suggests that, as of August 8, oviposition would be expected to occur across most of the southern prairies (Fig. 1). Model runs for the 2021 growing season (April 1 – August 8) predicted that oviposition should now be occurring across most of the prairies (Fig. 2).
Figure 1. Percent of grasshopper (Melanoplus sanguinipes) population in the egg stage across the Canadian prairies as of August 8 (based on climate normals data).Figure 2. Percent of grasshopper (Melanoplus sanguinipes) population in the egg stage across the Canadian prairies as of August 8, 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:
Wheat midge model simulations to August 8, 2021, predict that wheat midge populations should be in one of two larval stages. Where wheat midge is present, most larvae (55 %) will be in wheat heads, feeding on developing kernels. Development of this stage is predicted to be greatest across eastern Saskatchewan. Larvae that have completed development in wheat heads will be dropping to the soil where they will transition to larval cocoons (44 % of the prairie population). The occurrence of larval cocoons should be greatest across northwestern Saskatchewan and eastern Alberta. This stage will overwinter in the soil.
Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) larval population that is predicted to be in wheat heads as of August 8, 2021.Figure 2. Percent of the wheat midge (Sitodiplosis mosellana) larval population that is predicted to be in the soil (larval cocoons) as of August 8, 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!
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.
Agriculture and Agri-Food Canada has released the Canadian Crop Metrics application. This product contains useful and interesting information about the current status of crops grown across Canada. The application also presents data for a number of pest insects including bertha armyworm, diamondback moth, grasshoppers and wheat midge.
Read over the synopsis of the Canadian Crop Metrics application to gain a sense of what the resource has to offer and how to optimize access. It allows users to look at specific regions and generate reports, graphs, and tables to compare current conditions to historical conditions for 11 different crop types. Weather data is updated regularly and yield estimates are updated monthly from July to October.Forecasts are made at the beginning of the months of July, August and September for all crops, and an additional forecast is made for corn and soybeans (late season crops) at the beginning of October. Forecasts are jointly produced by Agriculture and Agri-Food Canada and Statistics Canada using historical yield, climate and satellite data as inputs.
Screenshots of the application are below for reference. Get started here!
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 August 8, 2021 (Fig. 1), C. tarsalis development has now reached the point that adults are predicted to be flying across the south of the prairies from Manitoba to Alberta. Outdoor enthusiasts falling within areas highlighted red (i.e., areas that have accumulated sufficient heat accumulation of >400 degree-days 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 August 8) should also start to use DEET this week!
Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of August 1, 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 August12, 2021). The screenshot below (retrieved 12Aug2021) serves as a reference and reports one human case of WNV, a positive wild bird, and positive mosquito pools 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 (retrieved 12Aug2021).
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.
The Field Heroes campaign continues to raise awareness of the role of beneficial insects in western Canadian crops.
Two NEW Field Heroes resources for 2021 include:
Real Agriculture went live in 2021 with Season 2 of the Pest and Predators podcast series! • NEW – Episode 12 – Get a jump on grasshoppers James Tansey (Saskatchewan Agriculture) and Shaun Haney (RealAg). Published online July 6, 2021. • Episode 11 – Free farm labour John Gavloski (Manitoba Agriculture and Resource Development) and Shaun Haney (RealAg). Published online June 15, 2021. • Episode 10 – Good bugs relocate for work Hector Carcamo(Agriculture and Agri-Food Canada-Lethbridge) and Shaun Haney (RealAg). Published online June 1, 2021. • Episode 9 – Secret agents in the stubble Jennifer Otani (Agriculture and Agri-Food Canada-Beaverlodge) and Shaun Haney (RealAg). Published online May 18, 2021. • Episode 8 – Good vs pea leaf weEVIL Meghan Vankosky (Agriculture and Agri-Food Canada-Saskatoon) and Shaun Haney (RealAg). Published online May 4, 2021. • Episode 7 – Powerful parasitoids: Better than fiction Tyler Wist (Agriculture and Agri-Food Canada-Saskatoon) and Shaun Haney (RealAg). Published online April 20, 2021. • Review SEASON 1 of the Pest and Predators podcast series!
The NEW Pests and Predators Field Guide is filled with helpful images for quick insect identification and plenty of tips to manage the pests AND natural enemies in your fields. Claim your free copy at http://fieldheroes.ca/fieldguide/ or download a free copy to arm your in-field scouting efforts!
Reminder – 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.
ALBERTA’SInsect 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.
With a common name that cites the devastation these insects brought upon crops during an 1848 outbreak in the Great Salt Lake Basin, Mormon crickets have equal potential to do damage on the Canadian Prairies. Like other grasshopper species, mormon crickets will consume various crops, including wheat, barley, alfalfa and sweet clover, in addition to other forages and garden vegetables. These crickets will also eat other insects, including smaller mormon crickets.
Droughts drive mormon cricket outbreaks, at which time these insects will have a greater economic impact on crops. Migrating swarms will consume all parts of their plant host, ravaging crops and reducing their marketable yields. In addition to this, baled alfalfa containing crickets is unpalatable to livestock, reducing its viability as a feed source.
Adults are 40-50 mm long with stout bodies. Their colour depends on how dense the population is: swarming mormon crickets can be black, brown, or red, and individual insects can be purple or green. Both the abdomen and the “shield” (pronotum) behind the crickets’ head may be striped. The females’ have a long egg-laying organ (ovipositor) and both sexes have antennae longer than their bodies. Mature nymphs resemble adults in colour and appearance but are somewhat smaller and females lack an ovipositor.
This past week (July 28 to August 3, 2020) prairie temperatures were warmest in southeastern Alberta and southwestern Saskatchewan and coolest in southern Manitoba and the Peace River region of Alberta and British Columbia (Fig. 1). Temperatures in the past week represent a switch from previous weeks, where it was warmer in Manitoba than in Alberta. Average 30-day temperatures (July 5 to August 3, 2020) continue to be cooler across most of Alberta than observed in eastern Saskatchewan and Manitoba (Fig. 2). The average 30-day temperature at Winnipeg and Brandon continued to be greater than locations in Alberta and Saskatchewan (Fig. 2).
Figure 1. Observed average temperatures across the Canadian prairies the past seven days (July 28-August 3, 2020).Figure 2. Observed average temperatures across the Canadian prairies the past 30 days (July 5-August 3, 2020).Figure 3. Mean temperature difference from Normal the past 30 days (July 1-31, 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, Saskatchewan and Manitoba (Fig. 4). Cumulative 30-day rainfall was lowest across a large area ranging from southwest Saskatchewan to Saskatoon (Fig. 5). Growing season rainfall (percent of average) is below normal across eastern Saskatchewan and localized areas of Manitoba and above normal across most of Alberta (Fig. 6).
Figure 4. Observed cumulative precipitation across the Canadian prairies the past seven days (July 28-August 5, 2020).Figure 5. Observed cumulative precipitation across the Canadian prairies the past 30 days (July 5-August 3, 2020).Figure 6. Percent of average precipitation for the growing season (April 1-August 3, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (04Aug2020). 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-August 3, 2020) is below (Fig. 7) while the growing degree day map (GDD) (Base 10 ºC, April 1-August 3, 2020) is shown in Figure 8.
Figure 7. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-August 3, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (06Aug2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209Figure 8. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-August 3, 2020). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (06Aug2020). 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 across the Canadian prairies the past seven days ranged from <24 to >32 °C (Fig. 9). So far this growing season (as of August 6, 2020), the number of days above 25°C ranges from 0-10 days throughout much of Alberta and into the BC Peace then extends up to 51-60 days in southern Manitoba (Fig. 10).
Model simulations for August 3, 2020, indicate that BAW development varies across the prairies. Figures 1 and 2 demonstrate that BAW populations near Winnipeg (Fig. 1) are more advanced than populations near Grande Prairie (Fig. 2). Populations near Winnipeg are predicted to be developing to pupae (Fig. 1). BAW populations near Grande Prairie are expected to be primarily in the larval stage (Fig. 2).
Figure 1. Predicted bertha armyworm (Mamestra configurata) phenology at Winnipeg MB as of August 3, 2020.Figure 2 Predicted bertha armyworm (Mamestra configurata) phenology at Grande Prairie AB as of August 3, 2020.
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 required to apply the economic threshold to manage both this pest and its natural enemies. For convenience, screen shots of the above maps or data have been placed below for Alberta, Saskatchewan, and Manitoba.
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.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 4) to help identify the economically important larvae. Review the 2019 Insect of the Week which featured bertha armyworm and its doppelganger, the clover cutworm!
Figure 4. 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.
Based on Harcourt (1954) the DBM model was run with a biofix of May 15, 2020. Model runs (as of August 3, 2020) were conducted with weather data for 2020 (Fig. 1) and climate normals (long term average temperatures). The first map illustrates that potentially three generations have been completed across Manitoba and southeastern Saskatchewan (Fig. 1). Most of the prairies have had two generations (Fig. 1). The second map, showing results for climate normal data, indicates that prairie populations should have completed two generations (Fig. 2).
Figure 1. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies as of August 3, 2020.Figure 2. Using a biofix date of May 15, 2020, the projected number of diamondback moth (Plutella xylostella) generations across the Canadian prairies using Climate Normal data.
The charts provide location specific details regarding potential development at Winnipeg (Fig. 3) and Lacombe (Fig. 4). The first chart illustrates DBM development at Winnipeg. Results indicate that there is potential for a fourth generation of DBM to occur in southern Manitoba. Populations near Lacombe are predicted to be completing the second generation.
Figure 3. Predicted diamondback moth (Plutella xylostella) phenology at Saskatoon SK. Values are based on model simulations (April 1-August 3, 2020).Figure 4. Predicted diamondback moth (Plutella xylostella) phenology at Lacombe AB. Values are based on model simulations (April 1-August 3, 2020).
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square). Beat them on to a clean surface and count the number of larvae (Fig. 5) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 5. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.Figure 6. Diamondback moth pupa within silken cocoon.
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).
As of August 3, 2020, the grasshopper model estimates that prairie grasshopper populations are primarily adults (Fig. 1). Based on model simulations, development has been slowest across central and northern regions of Alberta (Fig. 1). The second map provides an overview of where oviposition is predicted to have started (Fig. 2). The yellow and red areas show that oviposition has begun across southern Manitoba and southeastern Saskatchewan (Fig. 2).
Figure 1. Predicted average development stages of grasshopper (Melanoplus sanguinipes) populations across the Canadian prairies (as of August 3, 2020).Figure 2. Predicted oviposition for (Melanoplus sanguinipes) populations across the Canadian prairies (as of August 3, 2020).
The two graphs compare grasshopper development at Saskatoon (Fig. 3) and Brandon (Fig. 4). Near Saskatoon, grasshopper populations are expected to be mainly in the adult stage with oviposition beginning to occur over the past week (Fig. 3). Around Brandon, adult emergence is complete and oviposition should be well underway (Fig. 4).
Figure 3. Predicted grasshopper (Melanoplus sanguinipes) phenology at Saskatoon SK. Values are based on model simulations (April 1-August 3, 2020).Figure 4. Predicted grasshopper (Melanoplus sanguinipes) phenology at Brandon MB. Values are based on model simulations (April 1-August 3, 2020).
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.
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.
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).
Ladybird beetle larvae (Fig. 1), pupae (Fig. 2), and adults (Fig. 3) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids.
Figure 4. An aphid “mummy” adhered to a wheat awn. A “mummy” is the aphid host transformed to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge).
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 August 5, 2020 (Fig. 1), areas highlighted yellow and more imminently orange are approaching sufficient heat accumulation for mosquitoes to emerge. Areas highlighted red NOW HAVE Culex tarsalis flying (Fig. 1) – protect yourself by wearing DEET!
Figure 1. Predicted development of Culex tarsalis, across the Canadian prairies (as of August 5, 2020).
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 August 5, 2020 report. The summary indicates that, “Grasshoppers are currently the biggest insect concern. Some sunflower midge has been observed in sunflowers in the Eastern region, mainly around field edges, which is typical for this insect. Lygus bugs have also been noted in sunflower fields. Diamondback moth larvae in canola remains a concern for growers and agronomists in the Eastern region, with lots of scouting and some limited insecticide applications occurring.”
• Alberta Agriculture and Forestry’s Agri-News occasionally includes insect-related information or Twitter users can connect to #ABBugChat Wednesdays at 10:00 am.
This week’s Insect of the Week feature crop is oat, a plant grown across the Prairies for both food production and livestock feed. Our feature entomologist this week is Héctor Cárcamo.
Oat – AAFC
A versatile food and feed crop, almost 90% of Canadian oat production takes place across Manitoba, Saskatchewan and Alberta. In 2019 Canada was the world’s third largest oat producer, and number one oat exporter. In the same year, total Prairie production seeded over 1.3 million hectares (3.2 million acres) was over 3.8 million metric tonnes (4.2 million US tons).
Name: Héctor Cárcamo Affiliation: AAFC, Lethbridge Research and Development Centre Contact Information: hector.carcamo@agr.gc.ca
How do you contribute in insect monitoring or surveillance on the Prairies?
I contribute by helping to develop survey protocols for resurging native insect pests (wheat stem sawfly, 2003) or new invasive pests (pea leaf weevil, 2005; cereal leaf beetle, 2007). With my team we also conduct surveys to tackle research questions such as farm threshold validations or landscape studies for lygus bugs, cabbage seedpod weevil and cereal leaf beetle. Finally, I collaborate with various researchers in the writing of scientific articles from survey data.
In your opinion, what is the most interesting field crop pest on the Prairies?
It is difficult to name just one! I really like the wheat stem sawfly because it is so well studied and this allows us to ask more refined ecological questions. Plus it forces us to use non-chemical methods to manage it. But if I had to choose only one to work on…I would pick lygus bugs because they are an extremely challenging and complex pest with populations that can increase rapidly. It seems to be almost ‘unpredictable”! Also it is highly polyphagous and as a species complex, extremely widespread geographically – the tarnished plant bug ranges from Guatemala to Alaska!
What is your favourite beneficial insect?
Well, this is an easy one: a carabid ground beetle of course, my Twitter name gives this one away: @hectorcarabido! Why: because they are so diverse, easy to catch and easy to identify to species. They are also very popular so it is easy to start a conversation over carabid beetles with most entomologists.
Tell us about an important/interesting project you are working on right now.
I am excited about biological control and I am currently leading a national study on biocontrol of cabbage seedpod weevil and I am also equally excited to start the one that got delayed due to COVID-19: A survey of parasitism of lygus nymphs in emerging and established crops.
What tools, platforms, etc. do you use to communicate with your stakeholders?
I regularly do interviews with the farm media and work with the technology transfer platforms used by the various commodity associations that fund our research. I have also contributed to our AAFC fact sheets or other technology transfer publications. Recently I have started to use Twitter and I have participated regularly in the weekly #abbugchat.
Week 15 and our Staff are out performing surveys, in-field monitoring and are active at various tech-transfer events across the prairies! Please bookmark the Blog or subscribe to receive the latest growing season information!
Prairie temperatures continue to be cooler than average. Though temperatures this week were approximately 2 °C warmer than last week (July 8-14, 2019), the seven-day average temperature was 0.5 °C cooler than normal (Fig. 1). The warmest temperatures were observed across MB while temperatures were cooler in western SK and across AB.
Figure 1. Average temperature (°C) across the Canadian prairies the past seven days (July 8-14, 2019).
Across the prairies, 30-day (June 14 – July 14, 2019) average temperatures have been approximately 1 °C cooler than normal (Fig. 2). Average 30-day temperatures were 0 to 2 °C warmer than average across MB and 0 to 2 °C cooler than average in SK and AB. Growing season temperatures (April 1-July 14, 2019) have been 1 °C cooler than average; the warmest temperatures were observed across the southern prairies (Fig. 3).
Figure 2. Average temperature (°C) across the Canadian prairies the past 30 days (June 14-July 14, 2019). Figure 3. Average temperature (°C) across the Canadian prairies for the growing season (April 1-July 14, 2019). Figure 4. Mean temperature difference from Normal (°C) observed across the Canadian prairies the past 30 days (June 18-July 15, 2019). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (18Jul2019). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true
This past week significant rainfall amounts were reported MB and southeastern SK while minimal rainfall was reported across southwestern SK and southern AB (Fig. 5).
Figure 5. Cumulative precipitation observed the past seven days across the Canadian prairies (July 8-14, 2019).
Across the prairies, rainfall amounts for the past 30 days have been highly variable (Fig. 6). Dry conditions continue across much of southern AB. Rainfall was well above average in SK.
Figure 6. Cumulative precipitation observed the past seven days across the Canadian prairies (June 15-July 15, 2019).
Growing season (April 1 – July 14, 2019) rainfall amounts have been below average across southern regions of AB, central SK, and central MB (Fig. 7).
Figure 6. Cumulative precipitation observed over the growing season (April 1-July 15, 2019) across the Canadian prairies. Figure 7. Percent of average precipitation observed across the Canadian prairies for the growing season (April 1-July 17, 2019). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (18Jul2019). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true
Based on modeled soil moisture (Fig. 8), recent rains have improved soil moisture values across a large area of SK and MB. Predicted soil moisture continues to be low across large regions of southern and central areas of AB and western SK.
Figure 8. Modeled soil moisture (%) across the prairies (up to July 15, 2019).
The growing degree day map (GDD) (Base 5 ºC, April 1-July 14, 2019) is below (Fig. 9):
Figure 9. Growing degree day (Base 5 ºC) across the Canadian prairies for the growing season (April 1-July 14, 2019).
The growing degree day map (GDD) (Base 10 ºC, April 1-July 14, 2019) is below (Fig. 10):
Figure 10. Growing degree day (Base 10 ºC) across the Canadian prairies for the growing season (April 1-July 14, 2019).
The lowest temperatures (°C) observed the past seven days ranged from at least 14 down to at least 2 °C in the map below (Fig. 11).
Figure 11. Lowest temperatures (°C) observed across the Canadian prairies the past seven days (to July 17, 2019). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (18Jul2019). 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 less than 16 up to at least 30 °C in the map below (Fig. 12).
Figure 12. Highest temperatures (°C) observed across the Canadian prairies the past seven days (to July 17, 2019). Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (18Jul2019). 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.
Wheat Midge (Sitodiplosis mosellana) – Where wheat midge are present, cool, dry conditions in May and June have resulted in delayed emergence of adults. Wheat midge larvae have moved to the soil surface and pupae are appearing. In some locations adults should be beginning to emerge. The wheat midge model predicts that 44% (45% last week) of the population are in the larval cocoon stage and 37% (47% last week) of the population is predicted to have moved to the soil surface. This week 12% (7% last week) is predicted to be in the pupal stage. Adults continue to emerge in localized areas in localized areas across all three provinces.
The first map (Fig. 1) indicates the percent of the population that is in the pupal stage. The second map (Fig. 2) indicates that less than 10% of the adult population has emerged. The last map (Fig. 3) indicates that oviposition may be occurring in localized areas. 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 1. Predicted percent of wheat midge (Sitodiplosis mosellana) populations at PUPAL STAGE across the Canadian prairies (as of July 15, 2019). Figure 2. Predicted percent of wheat midge (Sitodiplosis mosellana) populations at ADULT STAGE across the Canadian prairies (as of July 15, 2019). Figure 3. Predicted percent of wheat midge (Sitodiplosis mosellana) populations where egg laying has begun across the Canadian prairies (as of July 15, 2019).
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.
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.
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.
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).
Cool temperatures continue to result in reduced grasshopper developmental rates. Based on model runs, approximately 7% (12.5% last week) of the population is in the first instar, 12% (23% last week) is predicted to be in the second instar, and 27% (32% last week) is in the third instar, 30% (21% last week) are predicted to be in the fourth instar and 18% (4% last week) are predicted to be in the fifth instar. As of July 14, 1% of melanopline species are predicted to be in the adult stage.
The following map (Fig. 1) indicates that grasshopper populations across the southern prairie are mostly in the third and fourth instars. Grasshopper development has been greatest near Winnipeg MB.
Figure 1. Predicted development stages of grasshopper (Melanoplus sanguinipes) populations across the Canadian prairies (as of July 15, 2019).
Last week, the Insect of the Week’s Doppelganger featured GRASSHOPPERS!!! Check out the excellent nymph photos to help your in-field scouting!
Bertha armyworm (Lepidoptera: Mamestra configurata) – Predictive model updates are completed for the growing season but can be reviewed here (Wk 14).
Important – Watch for updates from your provincial monitoring networks who are compiling cumulative pheromone-baited trap interceptions to assess risk levels in Alberta, Saskatchewan (updated 10Jul2019), and Manitoba (look on pg 7).
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.
Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting. Use the images below (Fig. 3) to help identify egg masses and the economically important larvae in canola.
Figure 3. Stages of bertha armyworm from egg (A), larva (B), pupa (C) to adult (D). Photos: J. Williams (Agriculture and Agri-Food Canada)
Now is the time to do in-field scouting for this insect pest. Review the Insect of the Week which features bertha armyworm and its doppelganger, the clover cutworm!
Lygus bugs (Lygus spp.) – The Insect of the Week’s doppelganger is the lygus bug versus the alfalfa plant bug. It includes tips to to discern the difference between these plant bug complexes when doing in-field scouting!
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 or French versions are available.
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 in-field CSPW scouting data then check the online map posted by Alberta Agriculture and Forestry (screenshot retrieved 18Jul2019 provided below as reference).
Diamondback moth (Plutellidae: Plutella xylostella) – Once diamondback moth is present in the area, it is important to monitor individual canola fields for larvae. Warm growing conditions can quickly translate into multiple generations in a very short period!
Monitoring:
Remove the plants in an area measuring 0.1 m² (about 12″ square), beat them on to a clean surface and count the number of larvae (Fig. 1) dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.
Figure 1. Diamondback larva measuring ~8mm long. Note brown head capsule and forked appearance of prolegs on posterior.
Figure 2. Diamondback moth pupa within silken cocoon.
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).
The Canadian Wildlife Health Cooperative compiles and posts information related to their disease surveillance for West Nile Virus in birds. Take note of the provincial distribution of positive WNV birds in 2018 (table posted below as reference).
The following is offered to predict when Culex tarsalis will begin to fly across the Canadian prairies (Fig. 2). Protect yourself by wearing DEET! This week, 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 in the map below (Fig. 2) are on the verge of approaching sufficient heat accumulation for mosquitoes to emerge. Areas highlighted lime green should be preparing for C. tarsalis flight.
Figure 2. Predicted development of Culex tarsalis, across the Canadian prairies (as of July 14, 2019).
Once adults emerge, the following map demonstrates how quickly a Culex tarsalis mosquito carrying WNV can become fully infective (i.e., when it has accumulated 109 base 14.3° degree days) – it’s a matter of days, depending on the region (Figure 3).
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):
• 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.
• July 25, 2019: SARDA Summer Field Tour, Falher, Alberta. Read more about this event. Entomologist participating: Jennifer Otani, Shelby Dufton.
• August 8, 2019: 2019 Wheatstalk to be held at Teepee Creek AB. View event info/registration details. Entomologists tentatively participating: Jennifer Otani, Shelby Dufton, 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.
Provincial entomologists provide insect pest updates throughout the growing season so we link to their most recent information:
• Manitoba‘s Crop Pest Updates for 2019 are posted here. Access Issue #9 posted July 17, 2019 which notes grasshopper, thistle caterpillar, green cloverworm and aphids in peas. There are also helpful photos and descriptions of grasshopper instar stages plus scouting tips to detect European corn borer egg masses.
The case of lygus bug versus the alfalfa plant bug: It is easy to understand why lygus bugs (Lygus spp.) and alfalfa plant bugs (Adelphocoris lineolatus) are difficult to tell apart as they are closely related, belonging to the same family (Hemiptera: Heteroptera). They are similar in appearance (long narrow body) with the alfalfa bug being slightly longer. Adult lygus bugs have a distinctive triangular or “V”-shaped marking in the upper centre of the their backs and membranous wingtips. The alfalfa plant bug has a similar marking but it is less distinct. One difference between the two is that lygus bug nymphs have five black dots over their thorax and abdomen which alfalfa bug nymphs lack.
Another difference is that lygus bugs have a broader host range that includes canola, alfalfa, soybean, sunflower, strawberry and several other crops. Alfalfa bugs have a much more particular palette and are mainly found in alfalfa crops and only occasionally feed on red and yellow sweet clover or canola when alfalfa is in short supply.
For more information about these species and more tips on telling them apart, see our Insect of the Week page!
Tarnished plant bug (Lygus lineolaris) – cc-by Scott Bauer Alfalfa plant bug (Adelphocoris lineolatus) – (c) Mike Dolinski. MikeDolinski@hotmail.com
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.
Review previously featured insects by visiting the Insect of the Week page.
Weather synopsis – This week, weather data is unavailable due to technical difficulties so we are unable to generate several maps. Please check webpages posted by Environment Canada for weather-related information.
Reminder – Pre-Harvest Interval (PHI) – Growers with late-season insect pest problems must factor in the PHI which is 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 and a PHI-value is 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.
An excellent summary of PHI for various pesticides in their various crops was posted by Saskatchewan Agriculture’s Danielle Stephens in 2016 within their Crop Production News.
In 2013, the Canola Council of Canada created and circulated their “Spray to Swath Interval Calculator” to help canola growers accurately estimate their PHI. Other PHI are described in your provincial crop protection guides and remember that specific crop x pesticide combinations will mean different PHIs.
Finally, work towards “Keeping It Clean” so your grain is ready for export! More information about PHI and Maximum Residue Limits (MRL) is available on the Keeping It Clean site.
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!
Review your province’s 2018 bertha armyworm pheromone trapping results towards the end of this Post.
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 14Aug2018 for reference):
Saskatchewan growers can check the 2018 bertha armyworm map (screenshot below retrieved 01Aug2018 for reference):
Manitoban growers can find bertha armyworm updates in that province’s Insect and Disease Updates. A screen shot of that summary (retrieved 01Aug2018) is pasted below:
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.
Thrips in canola (Thynsanoptera) – While scouting at this time of year, curled canola pods may be encountered. The culprits are quite possibly thrips.
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.
Curled pods of canola caused by thrips feeding damage (Photos: AAFC-Saskatoon, Olfert et al. 1998)
Read more about thrips in canola by accessing this article by Olfert et al. 1998).
Flea Beetles (Chrysomelidae: Phyllotreta species) – By early pod stages in canola, newly eclosed adult flea beetles begin to emerge from the soil. These individuals typically feed then move away from canola fields to locate overwintering habitats.
Normally, it can be difficult to locate these newly emerged adults but every few years they are easily observed among canola pods. These adults can feed on upper leaves and nip at the exterior of canola pods but are typically observed in low densities – too low to cause economic damage. Even so, be watchful – areas with high numbers of flea beetles late in the growing season are worthwhile to scout early in 2019.
Remember – the Action Threshold for flea beetles on canola is 25% of COTYLEDON LEAF AREA consumed.
Normally, it is NOT recommended to apply foliar insecticides for flea beetles in canola during the pod stages for the following reasons:
Flea beetles are very mobile at this point in the season,
Canola canopy is very thick,
Growers must be cautious about pre-harvest intervals,
PLUS, little is understood about overwintering survival of this pest!
Reminder – Earlier this season, the Insect of the Week featured flea beetles!
Refer to the flea beetle page from the “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.
Reminder – While scouting, you may encounter these fascinating organisms…..
Figure 1. Ladybird beetle larva (photo credit: AAFC-Beaverlodge)Figure 2. Ladybird beetle pupa (Left) and larva (Right) (photo credit: AAFC-Beaverlodge)Figure 3. Ladybird beetle pupa (photo credit: AAFC-Beaverlodge)Figure 4. Ladybird beetle (Coccinella septempunctata) (photo credit: AAFC-Beaverlodge)Figure 5. Aphids nestled on wheat head (photo credit: AAFC-Beaverlodge)Figure 6. An aphid “mummy” adhered to a wheat awn. Mummy is the aphid host converted to enclose a soon-to-emerge parasitoid wasp (photo credit: AAFC-Beaverlodge)
Ladybird beetle larvae (Fig. 1-2), pupae (Fig. 2-3), and adults (Fig. 4) can all be found in fields at this time of year. Take a look at the various stages and the many patterns of native and introduced species to recognize these as Field Heroes! Ladybird beetles are categorized as general predators and will feed on several species of arthropods but are partial to aphids (Fig. 5).
The Canadian Grain Commission is ready and willing to grade grain samples harvested in 2018. Samples are accepted up to November but send samples as soon a harvest is complete.
This is a FREE opportunity for growers to gain unofficial insight into the quality of their grain and to obtain valuable dockage information and details associated with damage or quality issues. The data collected also helps Canada market its grain to the world!
More information on the Harvest Sample Program is available at the Canadian Grain Commission’s website where growers can register online to receive a kit to submit their grain.
In exchange for your samples, the CGC assesses and provides the following unofficial results FOR FREE:
dockage assessment on canola
unofficial grade
protein content on barley, beans, chick peas, lentils, oats, peas and wheat
oil, protein and chlorophyll content for canola
oil and protein content and iodine value for flaxseed
oil and protein for mustard seed and soybean
NEW for 2018-19: Participants will receive Falling Number and deoxynivalenol (DON) results for their wheat samples at no cost. This enhancement to the Harvest Sample Program is the first initiative to be funded by the Canadian Grain Commission’s accumulated surplus.
Many producers find having both grade and quality information on their samples before delivering their grain to be helpful.
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 #11 (posted August 8, 2018) includes initial reports of very low levels of soybean aphids and reports of bertha armyworm in canola fields in western Manitoba yet few fields exceeding economic levels. Agronomists in southwest Manitoba reported “melting” bertha armyworm larvae-read more to learn how insect-specific viruses are at work in fields! Finally, a reminder that the annual grasshopper survey is underway in August.
Saskatchewan‘s Crop Production News for 2018 is posted with Issue #6 now available. This issue informs growers that Ministry staff will be in fields conducting surveys. A reminder to manage pre-harvest intervals plus read the article describing disease and insect culprits associated with white heads in cereals.
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 August 9, 2018) includes reports of the bertha armyworm in Birch Hills county, the expected appearance of red turnip beetles which feed, mate and lay eggs at this point in the growing season, relatively low numbers of diamondback moths but a reminder to scout in canola at early pod stages, and peculiar behaviours of parasitized ladybird beetles and grasshoppers.
This week’s Insect of the Week is the twospotted spider mite. This tiny mite is 0.5 mm long and has eight legs. It has a greenish, yellowish to orange oval body with two dark spots on its abdomen. To the unaided eye, it looks like a small speck. they feed on corn, soybean, dry beans, alfalfa, vegetables and fruit.
These mites overwinter in protected sites as eggs, immatures or adults depending on food hosts and habitat. Immatures and adults move to emerging plant hosts in the spring. They create webbing on the underside of leaves where they puncture cells to feed on cell contents. This feeding causes stippling, yellowing or browning of the leaves. Leaves may dry and drop which can further reduce crop yields.
Infestations start at the field edge and move inwards. Extended hot, dry conditions favour rapid population build up and exacerbate feeding injury.
For more information on the twospotted spider mite, check out our Insect of the Week page!
Twospotted spider mite – adult closeup David Cappaert, Michigan State University, Bugwood.orgTwospotted spider mite – stippling damage on bean Whitney Cranshaw, Colorado State University, Bugwood.org
