Weather synopsis

Jennifer Otani
Categories
Week 14

An abbreviated synopsis of the past week is provided below. Recent warm weather across the Canadian prairies helped crop development this past week

The growing degree day map (GDD) (Base 5 ºC, April 1-July 27, 2020) is below (Fig. 1) while the growing degree day map (GDD) (Base 10 ºC, April 1-July 27, 2020) is shown in Figure 2.

Figure 1. Growing degree day map (Base 5 °C) observed across the Canadian prairies for the growing season (April 1-July 27, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209
Figure 2. Growing degree day map (Base 10 °C) observed across the Canadian prairies for the growing season (April 1-July 27, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). 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 <22 to >34 °C (Fig. 3). So far this growing season (up to July 29, 2020), the number of days above 25 ranges from 0-10 days throughout much of Alberta and into the BC Peace then extends up to 41-50 days in southern Manitoba (Fig. 4).

Figure 3. Highest temperatures (°C) observed across the Canadian prairies the past seven days (April 1-July 29, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209
Figure 4. Number of days above 25 °C observed across the Canadian prairies this growing season (April 1-July 29, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). 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 with the exception of around Regina south to the American border, and southwest Manitoba west into the southeast corner of Saskatchewan (Fig. 5). Cumulative 30-day (Fig. 6) and rainfall for the growing season (April 1-July 29, 2020; Fig. 7) are below.

Figure 5. Observed cumulative precipitation across the Canadian prairies the past seven days (as of July 29, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209
Figure 6. Observed cumulative precipitation across the Canadian prairies the past 30 days (as of July 29, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209
Figure 7. Observed cumulative precipitation across the Canadian prairies for the growing season (as of July 29, 2020).
Image has not been reproduced in affiliation with, or with the endorsement of the Government of Canada and was retrieved (30Jul2020). Access the full map at http://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true&reset=1588297059209

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

Wheat midge

Jennifer Otani
Categories
Week 14

Click to link to last week’s information posted for Wk 13 (released 23Jul2020) to review the predictive model outputs for this insect pest.

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 15 ºC), calm evenings, the midge can be observed in the field, laying their eggs on the wheat heads (Fig. 1). 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.

Figure 1. Wheat midge (Sitodiplosis mosellana) laying their eggs on the wheat heads 
(Photo: AAFC-Beav-S. Dufton & A. Jorgensen).

REMEMBER that in-field counts of wheat midge per head remain the basis of economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 2), 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.

Figure 2. Macroglenes penetrans, a parasitoid wasp that attacks wheat midge, measures only ~2 mm long.  (Photo: AAFC-Beav-S. Dufton).

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 in 2019 (for Wk11).  Review that post for descriptions and photos to help with in-field scouting for this economic pest of wheat!  Additionally, the differences between midges and parasitoid wasps were featured as the current Insect of the Week in 2019 (for Wk12).  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.

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

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

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

Bertha armyworm

Jennifer Otani
Categories
Week 14

Click to link to last week’s information posted for Wk 13 (released 23Jul2020) to review the predictive model outputs for this insect pest. As larvae now begin to develop and feed in fields, emphasis is now placed on in-field scouting in areas where high moth counts are being intercepted by provincial networks highlighted below.

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 AlbertaSaskatchewan and Manitoba. 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 available maps or data from Alberta, Saskatchewan, and Manitoba are below.

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Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting.  Use the images above (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! 

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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 ManitobaSaskatchewanAlberta 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.

Diamondback moth

Jennifer Otani
Categories
Week 14

Diamondback moth (Plutellidae: Plutella xylostella) – Once the 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.

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Figure 1. Diamondback larva measuring ~8mm long.
Note brown head capsule and forked appearance of prolegs on posterior.
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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  (approximately 2-3 larvae per plant).  Economic thresholds for canola or mustard in the early flowering stage are not available. However, insecticide applications are likely required at larval densities of 10 to 15 larvae/ 0.1 m² (approximately 1-2 larvae per plant).

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Figure 3. Diamondback moth.

Biological and monitoring information for DBM is posted by Manitoba AgricultureSaskatchewan Agriculture, and the Prairie Pest Monitoring Network.  

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

Lygus bug monitoring

Jennifer Otani
Categories
Week 14

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.  

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Figure 1. Adult Lygus lineolaris (5-6 mm long) (photo: AAFC-Saskatoon).
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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). 

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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. 

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

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

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

Field heroes

Jennifer Otani
Categories
Week 14

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

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

• Access Episode 1 – Do you know your field heroes?

• Access Episode 2 – An inside look at the Prairie Pest Monitoring Network.

• Access Episode 3 – How much can one wasp save you?

• Access Episode 4 – Eat and be eaten — grasshoppers as pests and food

• Access Episode 5 – Killer wasp has only one target — wheat stem sawfly

• Access Episode 6Plentiful parasitoids

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

West nile virus risk

David Giffen and Jennifer Otani
Categories
Week 14

Health Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through humanmosquitobird and horse surveillance.  Link here to access the most current weekly update (July 5-11, 2020; retrieved July 30, 2020). The screenshot below (retrieved July 30, 2020) serves reference but access that information here.

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The following is offered to predict when Culex tarsalis, the vector for West Nile Virus, will begin to fly across the Canadian prairies (Fig. 1). This week, regions most advanced in degree-day accumulations for Culex tarsalis are shown in the map below (yellow, orange then red highlighted areas).  As of July 30, 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 July 30, 2020).

Provincial insect pest report links

Jennifer Otani
Categories
Week 14

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

Manitoba‘s Crop Pest Updates for 2020 are available. Access the July 29, 2020 report. The summary indicates that, “Grasshoppers are the insect of greatest concern to field crops in Manitoba currently. Some populations of diamondback moth above economic threshold have been found in eastern Manitoba recently.”

Saskatchewan‘s Crop Production News (for Issue 6). Read Issue 5 which includes articles on Bertha armyworm, Cabbage seedpod weevil,  FieldWatch – Fostering Communication Between Applicators and Producers, and Look What the Wind Blew in! Diamondback Moths Arrived Early This Spring. Issue #4 included articles on Pest Scouting 101: Mid-Summer, and The Wheat Midge.

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

Crop report links

Jennifer Otani
Categories
Week 14

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

• Manitoba Agriculture and Rural Initiatives – Other viewing options include subscribing to receive or access a PDF of July 28, 2020 report.

• Saskatchewan Agriculture  or access a PDF of July 21-27, 2020 report.

• Alberta Agriculture and Forestry or access a PDF of July 14, 2020 report.

The following crop reports are also available:

• The United States Department of Agriculture (USDA) produces a Crop Progress Report (read the July 27, 2020 edition).

• The USDA’s Weekly Weather and Crop Bulletin (read the July 28, 2020 edition). 

Previous posts

Jennifer Otani
Categories
Week 14


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

    • 2019-2020 Risk and forecast maps

    • Alfalfa weevil (Wk08)

    • Aster leafhopper (Wk05)

    • Beetle data please! (Wk03)

    • Cereal aphid APP (Wk11)

    • Crop protection guides (Wk02)

    • Cutworms (Wk02)

    • Diamondback moth (Wk11)

    • Flea beetles (Wk02)

    • John Doane (Wk10)

    • Monarch migration (Wk10)

    • Pea leaf weevil (Wk11)

    • Pea leaf weevil – predicted development (Wk09)

    • Prairie provincial insect webpages (Wk02)

    • Predictive model updates: Bertha armyworm, Grasshoppers, Wheat midge (Wk13).

    • Scouting charts – canola and flax (Wk02)

    • Ticks and Lyme Disease (Wk06)

    • Wind trajectories (Wk09)

Sweet Clover Pests / Feature Entomologist: Sean Prager

Finch Van Baal
Categories
Week 14

This week’s Insect of the Week featured crop is sweet clover: a soil-building, weed suppressing legume. Our feature entomologist this week is Sean Prager.

Sweet clover
cc by 2.0 Phil Gayton

Native to Turkey, Canadian sweet clover includes plants developed from Spanish and Siberian sources. Tolerant to cold, drought and various soil textures, sweet clover is a robust crop that is grown across the Prairies. Sweet clover has a taproot that can grow as deep as 1. 5 metres (5 feet) by the end of spring, adding nitrogen and organic matter to soil. As a forage grazed by livestock, it achieves maximum palatability and feed quality between 25 and 35 centimetres (10-14 inches) in height, as it reaches the bud stage. As sweet clover matures, it loses its palatability. Sweet clover contains a unique chemical called coumarin. When sweet clover is exposed to mold growth, coumarin is converted into the anticoagulant dicoumarol, which poses a risk to livestock consuming contaminated hay or silage. For this reason, proper harvesting of sweet clover for hay or silage is essential.

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

Sweet clover plant
cc by 2.0 Des Blenkinsopp
Sweet clover pests
  • Alfalfa caterpillar
  • Army cutworm
  • Beet webworm
  • Blister beetle
  • Clover root weevil
  • Grasshoppers
  • Mormon crickets
  • Sweet clover weevil
  • Variegated cutworm
Sweetclover weevil – AAFC

Entomologist of the Week: Sean Prager

Name: Sean Michael Prager
Affiliation: Department of Plant Sciences, University of Saskatchewan
Contact Information:
sean.prager@usask.ca
306-361-8525
Agriculture Building, 51 Campus Drive, Saskatoon, SK S7N 5A8

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

I coordinate the Lygus surveys in faba bean as part of the provincial monitoring and survey efforts in Saskatchewan. Our lab also occasionally conducts other studies that result in pest information for crops in the prairies.

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

The first insects I worked on were mosquitoes. Because of that experience, I have always been really interested in disease vectors. On the Prairies, Aster Leafhoppers are a vector and pest that have some pretty neat aspects to their biology. They can be a major problem in canola; although the events are rare. Finally, they are also really useful for many of the ecological questions our lab asks.

What is your favourite beneficial insect?

As a postdoc, I studied a small parasitoid wasp called Aphelinus rhamni. It is a species that parasitizes aphids, especially soybean aphid. It was collected in Asia and has potential as a classical biological control agent.

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

I think the work we are doing to develop thresholds for aphids in pulse crops will be very useful on the Prairies and is quite interesting. Similarly, the work we have been doing on Lesser clover leaf weevils in red clover has been interesting as well and will hopefully be important to industry.

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

We use many of the standard tools. My lab has a website (www.pragerlab.ca), a twitter account (@USaskENt), and Instagram. We are more active in some places than others. In addition to that, members of my lab often attend field days and grower meetings.


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