Released August 23, 2024

Jennifer Otani
Categories
Week 16

Welcome to Week 16 – the final Weekly Update of the 2024 growing season! We wish everyone good harvest weather AND a speedy, amicable resolution to the rail labour dispute that started Thursday morning. This week includes:
• Weather synopsis
• Pre-harvest intervals (PHI)
• Bertha armyworm
• Diamondback moth
• Grasshopper
• Crickets
• West nile virus
• Provincial insect pest report links
• Crop report links
• Previous posts

Catch Monday’s Insect of the Week for Week 16 – What’s eating my crop? Wheat stem sawfly

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

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Weather synopsis

Jennifer Otani
Categories
Week 16

A full weather summary is not available this week.

Growing degree day (GDD) dynamic maps for the Canadian prairies for Base 5 ºC and Base 10 ºC (April 1-August 19, 2024) can be viewed by clicking the hyperlinks. Over the past 7 days (to August 21, 2024), the lowest temperatures recorded across the Canadian prairies ranged from 1 to 13 °C while the highest temperatures observed ranged from 4 to 32 °C. In terms of precipitation across the Canadian prairies. Review the growing season accumulated precipitation (April 1-August 21, 2024), the growing season percent of average precipitation (April 1-August 21, 2024), and the past 7 days (as of August 21, 2024). Access these maps and more using the AAFC Maps of Historic Agroclimate Conditions interface.

When it comes to wildfire smoke and air quality indices – did you know you can click to find….
• 72 hr projections of Ground Level Wildfire Smoke Fine Particulate Matter (PM 2.5) for the Canadian prairies using this link
• Tabular summaries of Air Quality Heatlh Index values and forecast maximums for the provinces of Manitoba, Saskatchewan, Alberta, or British Columbia.

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

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Pre-Harvest Intervals (PHI)

Jennifer Otani
Categories
Week 16

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.

Helpful resources include:
• The Keep It Clean website, with information about PHI and Maximum Residue Limits (MRL)
• The Pest Management Regulatory Agency fact sheet, “Understanding Preharvest Intervals for Pesticides”, with a free copy available to download
• Keep It Clean’s “Pre-Harvest Interval Calculator” helps to accurately estimate PHI for a variety of crops
• The Pre-Harvest Glyphosate Stage Guide
• The provincial crop protection guides include the PHI for every pesticide by crop combination. The 2023 Crop Protection Guides are available as FREE downloadable PDFs for Alberta, Saskatchewan, and Manitoba for 2024!

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Bertha armyworm

Jennifer Otani and Meghan Vankosky
Categories
Week 16

Access the Provincial Insect Pest Report for Wk16 for updates for this economic insect pest.

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

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

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

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

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Diamondback moth

Jennifer Otani and Meghan Vankosky
Categories
Week 16

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 Wk16 for updates for this economic insect pest.

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

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Grasshopper

Jennifer Otani, James Tansey and Meghan Vankosky
Categories
Week 16

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 Wk16 for updates for this economic insect pest.

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

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Crickets

Jennifer Otani and John Gavloski
Categories
Week 16

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. Technically not a true cricket, Mormon crickets are katydids as they belong to the Family Tettigoniidae). 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.

True crickets include the field, ground, camel and tree crickets which belong to the Family Gryllidae. 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.

Many species of crickets are distributed across the Canadian prairies. In addition to the Mormon cricket, 17 species of true crickets can be observed in Manitoba! The Mormon cricket was featured as the Insect of the Week back in 2021 and images of the fall field cricket can be viewed online at Bug Guide. Check out the Bug Guide link to the “Singing insects of North America” to learn more about fall field crickets!

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.

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West nile virus

Jennifer Otani
Categories
Week 16

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:

LocationDegree Days (base 14.3 °C) as of August 21, 2024Observed date heat units >200 Degree DaysPotential date when >390 Degree Days attained
Winnipeg384.0July 20August 24
Brandon302.8July 27Unable to project
Regina352.9July 26September 2
Saskatoon320.4July 29Unable to project
Lethbridge331.2July 25Unable to project
Edmonton205.9August 20Unable to project
Grande Prairie239.2August 11Unable 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.

The Public Health Agency of Canada posts information related to West Nile Virus in Canada. Link here to view the latest case numbers and seasonal updates. 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. Access information on surveillance posted by the provinces of Manitoba, Saskatchewan, or Alberta.

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Provincial insect pest report links

Jennifer Otani, John Gavloski, James Tansey, Carter Peru and Shelley Barkley
Categories
Week 16

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

MANITOBA’S Crop Pest Updates for 2024 are available. Access the 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:
• Aphids – “Soybean aphids levels are high in some areas” with “insecticides applied to a few soybean fields in the Eastern region” but “a lot of lady beetles” have been reported from some soybean fields. The report includes photos of lady beetle larvae to help producers identify sevenspotted, multicoloured Asian, thirteenspotted, and sevenspotted larvae. An action threshold for soybean aphids (R1-R5 growth stages) is an average of >250 aphids per plant but is no longer applicable past the R5 stage. Access the Manitoba Pulse Growers “soybean growth staging guide” to differentiate plant stages.
• Other aphid predators – Photos of a hover fly larva, damsel bug adult, green lacewing larva, and minute pirate bug adult are featured in the report.
• 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.

SASKATCHEWAN’S Crop Production News is back for the 2024 growing season! Access the online Issue #7 report. Bookmark their insect pest homepage to access important information! Also access the Crops Blog Posts that released a grasshopper activity update (June 2024), announced registration for the Crop Diagnostic School 2024 but also posts help for scouting fields for wireworms (May 2024), grasshopper identification: pest or not (Apr 2024), a summary of wheat midge populations and management (Mar 2024), and a description of pea leaf weevil populations (Feb 2024).

ALBERTA’S Insect Pest Monitoring Network webpage links to insect survey maps, live feed maps, insect trap set-up videos, and more. There is also a Major Crops Insect webpage. Remember, AAI’s Agri-News occasionally includes insect-related information, e.g., 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.

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Crop report links

Jennifer Otani
Categories
Week 16

Access the latest provincial crop reports produced by:
• Manitoba Agriculture (or access a PDF copy of the August 20, 2024 report).
• Saskatchewan Agriculture (or access a PDF copy of the August 13-19, 2024 report).
• Alberta Agriculture and Irrigation (or access a PDF copy of the August 13, 2024 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 August 19, 2024 edition).
• The USDA’s Weekly Weather and Crop Bulletin (access a PDF copy of the August 19, 2024 edition).

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Previous posts

Jennifer Otani
Categories
Week 16

As the growing season progresses, the Weekly Update topics move on and off the priority list for in-field scouting. It remains useful to keep the list at hand to support season-long monitoring. Click to review these earlier 2024 Posts (organized alphabetically):
• 2023 Risk maps
• Alfalfa weevil (Wk 09)
• Aphids in field crops (Wk 15)
• Bertha armyworm (Wk 15)
• Cabbage seedpod weevil (Wk 10)
• Canola flower midge (Wk 13)
• Cereal leaf beetle (Wk 10)
• Cicada – Rare co-emergence of broods (Wk07)
• Crop production guide links (Wk 03)
• Diamondback moth (Wk 15)
• European skipper (Wk 11)
• Cutworms (Wk 05)
• Field heroes (Wk 05)
• Flea beetles (Wk 04)
• Invasive insects (Wk 06)
• Monarch migration (Wk 10)
• Pea leaf weevil (Wk 05)
• Prairie Crop Disease Monitoring Network (Wk 08)
• Prairie Weed Monitoring Network (Wk 06)
• Scouting charts – canola and flax (Wk 03 of 2022)
• Tick tips (Wk 04)
• True armyworm (Wk 09)
• Wind trajectory summaries unavailable (Wk 01)
• Wheat midge (Wk 11)

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