Released July 22, 2022

Jennifer Otani
Categories
Week 11

This week includes…..

• Weather synopsis
• Predicted wheat midge development
• Predicted grasshopper development
• Predicted diamondback development
• West Nile virus risk
• Pre-harvest intervals (PHI)
• Provincial entomologist updates
• Links to crop reports
• Previous posts
….and Monday’s Insect of the Week for Week 11 – it’s European corn borer (Ostrinia nubilalis)!

Wishing everyone good SCOUTING weather!

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Weather synopsis

Ross Weiss, Tamara Rounce, David Giffen, Owen Olfert, Jennifer Otani and Meghan Vankosky
Categories
Week 11

TEMPERATURE: Though recent temperatures have been warmer than normal, the 2022 growing season across the prairies continues to be marginally cooler than average. This past week (July 11-17, 2022) the average daily temperature (prairies) was 2.5 °C warmer than last week. Coolest temperatures were observed across Alberta (Fig. 1). The prairie-wide average 30-day temperature (June 18 – July 17, 2022) was 1.5 °C warmer than the long-term average value. Average temperatures have been warmest across the southern prairies, particularly across Saskatchewan and Manitoba (Fig. 2).

Figure 1. Seven-day average temperature (°C) across the Canadian prairies for the period of July 11-17, 2022.
Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 18-July 17, 2022.

The average growing season (April 1-July 17, 2022) temperature for the prairies has been 0.3 °C cooler than climate normal values. The growing season has been warmest across the southern prairies (Fig. 3).

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to July 17, 2022.

PRECIPITATION: Weekly (July 11-17, 2022) rainfall varied across the prairies. Highest rainfall amounts were reported across southern Manitoba and southeastern Saskatchewan (Fig. 4). Observed rainfall events across Alberta were generally less than 5 mm. The 30-day (June 18 – July 17, 2022) rainfall amounts have been well below average for the Peace River region, average to above average for Alberta, below normal for Saskatchewan and near normal to above normal across Manitoba (Fig. 5).

Figure 4 Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 11-17, 2022.
Figure 5. 30-day cumulative rainfall (mm) observed across the Canadian prairies the past 30 days (June 18-July 17, 2022).

Growing season rainfall for April 1 – July 17, 2022, continues to be greatest across Manitoba and eastern Saskatchewan; cumulative rainfall amounts have been much lower for central and western regions of Saskatchewan and Alberta (Fig. 6).

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to July 17, 2022.

Growing degree day (GDD) maps for Base 5 ºC and Base 10 ºC (April 1-July 18 2022) can be viewed by clicking the hyperlinks. Over the past 7 days (July 12-18, 2022), the lowest temperatures recorded across the Canadian prairies ranged from < 2 to >14 °C while the highest temperatures observed ranged from <25 to >37 °C. Review the days at or above 25 °C across the prairies and also the days at or above 30 °C. Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

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

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Predicted wheat midge development

Ross Weiss, Tamara Rounce, David Giffen, Owen Olfert, Jennifer Otani and Meghan Vankosky
Categories
Week 11

The following maps represent predicted regional estimates of wheat midge development. Remember – the rate of development and density varies at the field level and can only be verified through in-field scouting. Midge flight coinciding with the beginning of anthesis is a crucial point when in-field counts of adults on plants are carefully compared to the economic thresholds!

As of July 17, 2022, where wheat midge are present, model simulations predict that eggs and larvae (in heads) are the two prevalent stages occurring across the prairies. Differences in wheat midge development are attributed to rainfall differences across the prairies. Optimal rain events in May and June across Saskatchewan and Manitoba have contributed towards and advanced development rates of WM populations whereas populations in southern and central Alberta remain largely in the adult stage (Fig. 1). Adult populations in Saskatchewan and Manitoba are predicted to have peaked and are declining. Populations in the Peace River region are predicted to be primarily in the egg stage (Fig. 2). Across Manitoba and Saskatchewan, populations are predicted to be transitioning from the egg stage to the larval stage (Fig. 3).

Figure 1. Percent of wheat midge larval population (Sitodiplosis mosellana) that is in the pupal stage, across western Canada, as of July 17, 2022.
Figure. 2. Percent of wheat midge population (Sitodiplosis mosellana) that is in the egg stage across western Canada, as of July 17, 2022.
Figure 3. Percent of wheat midge population (Sitodiplosis mosellana) that is in the larval stage (in wheat heads), across western Canada, as of July 17, 2022.

Wheat midge development can be very site specific. For example, (as of July 17, 2022) developmental rates near Regina, Saskatchewan were predicted to be greater than for Yorkton, Saskatchewan, and Grande Prairie, Alberta. Model simulations indicate that populations near Regina were predominantly in the larval stage (Fig. 4) while Yorkton and Grande Prairie populations were predicted to be predominantly eggs (Figs. 5 and 6).

Figure 4. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Regina, Saskatchewan as of July 17, 2022.
Figure 5. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Yorkton, Saskatchewan as of July 17, 2022.
Figure 6. Predicted development of wheat midge (Sitodiplosis mosellana) and wheat development near Grande Prairie, Alberta, as of July 17, 2022.

In-Field Monitoring: When scouting 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. 5). 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 5. Wheat midge (Sitodiplosis mosellana) laying their eggs on a wheat head. Photo: AAFC-Beav-S. Dufton and A. Jorgensen.

REMEMBER that in-field counts of wheat midge per head remain the basis of the economic threshold decision.  Also remember that the parasitoid, Macroglenes penetrans (Fig. 6), is actively searching for wheat midge at the same time.  Preserve this parasitoid whenever possible and remember insecticide control options for wheat midge also kill these beneficial insects who help reduce midge populations.

Figure 6. 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 No. 1 grade: 1 adult midge per 8 to 10 wheat heads during the susceptible stage.
b) To maintain 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 larval damage.

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

Information related to wheat midge biology and monitoring can be accessed by linking to your provincial fact sheet (Saskatchewan Agriculture or Alberta Agriculture & Forestry).  Alberta Agriculture and Forestry has a YouTube video describing in-field monitoring for wheat midge.  

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

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Predicted grasshopper development

Ross Weiss, Tamara Rounce, David Giffen, Owen Olfert, Jennifer Otani and Meghan Vankosky
Categories
Week 11

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 but local development can vary and is only accurately assessed through in-field scouting.

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

Model simulations were used to estimate grasshopper development as of July 17, 2022. Based on estimates of average nymphal development, populations should consist of primarily in the 4th and 5th instar and adults across southern regions of all three prairie provinces (Fig. 1). Adults should now be occurring across southern regions of all three prairie provinces (Fig. 2).

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

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

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

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Predicted diamondback moth development

Ross Weiss, Tamara Rounce, David Giffen, Owen Olfert, Jennifer Otani and Meghan Vankosky
Categories
Week 11

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

Model simulations to July 17, 2022, indicate that the second generation of non-migrant adults (based on mid-May arrival dates) are currently occurring across the Canadian prairies (Fig. 1). This week, development of the second generation has expanded across most of the Peace River region and the third generation is predicted to occur in a localized region of southern Manitoba. DBM development is predicted to be similar to average values (Fig. 2).

Figure 1. Predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 17, 2022.
Figure 2. Long-term predicted number of non-migrant generations of diamondback moth (Plutella xylostella) expected to have occurred across the Canadian prairies as of July 17, based on climate normal data.

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

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

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

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

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

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

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

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West nile virus risk

David Giffen, Phil Curry, Owen Olfert, Jennifer Otani and Meghan Vankosky
Categories
Week 11

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

As of July 17, 2022, C. tarsalis development is now on the verge of the second generation of adults beginning to fly in areas highlighted yellow (i.e., 250-300 DD of base 14.3 °C) represented below in Figure 1. Outdoor enthusiasts falling within areas highlighted orange or yellow should begin to wear DEET to protect against WNV! Historically, southern and central regions of the Canadian prairies are now entering a period of increased risk for WNV that typically peaks over the long weekend in August.

Figure 1. Predicted development of Culex tarsalis across the Canadian prairies (as of July 17, 2022).

For those following the specifics of the mosquito host-WNV interaction, Figure 2 projects how many days it will take a C. tarsalis female to become fully infective and be able to transmit the virus to another host (bird or human) once the virus is acquired from another bird. This represents the extrinsic incubation period (EIP) of the virus within the mosquito. Figure 2 projects the EIP is approximately 14 days in areas highlighted red.

Figure 2. Predicted extrinsic incubation period (EIP) of West Nile Virus within a C. tarsalis female as of July 17, 2022.

The above maps should be compared with historical confirmed cases of WNV. The Public Health Agency of Canada posts information related to West Nile Virus in Canada and also tracks West Nile Virus through human, mosquito, bird and horse surveillance. Link here to access their most current weekly update (reporting date November 18, 2021; retrieved July 20, 2022). The screenshot below (retrieved 20Jul2022) serves as a background reference of what was reported in 2021.

Bird surveillance continues to be an important way to detect and monitor West Nile Virus. The Canadian Wildlife Health Cooperative (CWHC) works with governmental agencies (i.e., provincial laboratories and the National Microbiology Laboratory) and other organizations to report the occurrence of WNV. Dead birds retrieved from areas of higher risk of West Nile Virus are tested for the virus. A screenshot of the latest reporting results posted by Canadian Wildlife Health Cooperative is below (retrieved 20Jul2022).

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.

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Pre-Harvest Intervals (PHI)

Jennifer Otani
Categories
Week 11

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.
• 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.

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Provincial insect pest report links

Jennifer Otani, John Gavloski, James Tansey, Carter Peru and Shelley Barkley
Categories
Week 11

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

MANITOBA’S Crop Pest Updates for 2022 are up and running! Access a PDF copy of the July 20, 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!
Grasshoppers and pea aphids in MB were emphasized in the July 20 issue.
Bertha armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 20, 2022) of cumulative weekly counts.
Armyworm pheromone trap monitoring is underway in MB – Review this summary (as of July 12, 2022) of counts compiled from Manitoba, Eastern Canada and several northeast states of the United States.

SASKATCHEWAN’S Crop Production News for 2022 is up and running! Access the online Issue #4 (July 14, 2022) here and find updates linking to information for Wheat stem sawfly. Bookmark their insect pest homepage to access important information! Crops Blog Posts are updated through the growing season and note this link for July’s Crop Diagnostic School.

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

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Crop report links

Jennifer Otani
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Week 11

Click the provincial name below to link to online crop reports produced by:
Manitoba Agriculture and Resource Development (or access a PDF copy of the July 19, 2022 report).
Saskatchewan Agriculture (or access a PDF copy of the July 5-11, 2022 report).
Alberta Agriculture, Forestry, and Rural Economic Development (or access a PDF copy of the July 12, 2022 report).

The following crop reports are also available:
• The United States Department of Agriculture (USDA) produces a Crop Progress Report (access a PDF copy of the July 18, 2022 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the July 19, 2022 edition).

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Previous posts

Jennifer Otani
Categories
Week 11

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

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EUROPEAN CORN BORER: A GENERALIST PEST OF CROPS

Meghan Vankosky, Tracey Baute, Jocelyn Smith, John Gavloski and Cynthia Schock
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Week 11

Despite its common name, the European corn borer (Ostrinia nubilalis) feeds on many crop and non-crop plants including beans, potato, quinoa, millet, hemp, wheat, many vegetables and some flowers. European corn borer is occasionally an economic pest of crops such as corn and potatoes in Manitoba, where there is one generation per year. In parts of Ontario and eastern Canada, there are univoltine (one generation per year) and bivoltine (two generations per year) strains. How prevalent and damaging European corn borer is to many of its host crops is still not clear.

European corn borer has traditionally been monitored in corn fields, and more recently in potato fields. However, a new harmonized protocol can be used to monitor for European corn borer in multiple crops. Anyone participating in insect monitoring on any potential host crop can access the harmonized protocol online or using the Survey123 app.

The protocol can be used to report the presence of European corn borer eggs, larvae, and crop damage. Anyone monitoring populations or encountering noticeable levels of European corn borer or their injury to any crop is highly encouraged to add this data. For more information about the harmonized protocol and to submit monitoring data, please click here to access all needed links. Information collected from across Canada will be used to better understand the distribution, feeding habits, and abundance of this pest.

European Corn Borer egg masses. Photo credit: John Gavloski, Manitoba Agriculture

Access these resources to find more information:
• Review the European corn borer page within the “Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and management field guide” (2018) also accessible as a free downloadable PDF in either English or French on our new Field Guides page.
• Review the Manitoba Agriculture fact sheet for the European corn borer.
• Review the Ontario Ministry of Agriculture, Food, and Rural Affairs fact sheet for European corn borer.

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