2023 Week 13 (Released August 3, 2023)

Meghan Vankosky
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Week 13

Insect scouting season continues! Development of many pest insects (and of their host crops) is ahead of schedule this year, thanks to warmer than average weather during this growing season.

Between fieldwork and summer vacations, this Weekly Update is a short one. Thankfully, Shelley Barkley (Alberta Agriculture and Irrigation), James Tansey (Saskatchewan Ministry of Agriculture) and John Gavloski (Manitoba Agriculture) have kindly shared information about what they are seeing for insect pests in their respective prairie provinces.

Adult grasshoppers are now in flight and are expected to be busy reproducing across the prairie region. Scouting individual fields is important to best estimate crop risk. Information about grasshoppers and grasshopper monitoring is available from the Prairie Pest Monitoring Network, in the Field Crop and Forage Pests guide, Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, and Manitoba Agriculture. 

Adult (brown with fully developed wings) and immature (green with wing ‘nubs’). Picture by Meghan Vankosky, AAFC-Saskatoon.

Diamondback moth, if present, should now be well into their fourth generation across the prairies. As warm temperatures prevail, remember that diamondback moth develop from eggs to adults quickly and the population increases with each generation. Scout canola fields for 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.

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

On the topic of invasive insects, August is Tree Check Month! The Prairie Region Poster (and posters for BC, Ontario & Quebec, and Atlantic Canada) include invasive insect pests that could affect our forests in Canada.

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

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

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

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Provincial Insect Updates

Shelley Barkley, John Gavloski, James Tansey and Meghan Vankosky
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Week 13

In Alberta, grasshopper population densities are high in the southeast and southcentral municipalities and the Agricultural Fieldmen are now starting to survey for adult grasshopper populations. There have been reports of wheat head armyworm in the central Peace River region, but there have also been Cotesia parasitoid cocoons in those fields, which is a good sign in terms of natural control of the armyworm population. Tiger moth caterpillars have also been reported in the central Peace River region; these are not typically pests but are interesting as they have been feeding on wild buckwheat.

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.

Grasshopper densities are high in many parts of the prairies this year, especially now that adult grasshoppers are able to fly to disperse. With adults present, egg laying is likely to be underway. Picture by Jonathon Williams, AAFC-Saskatoon.

In Saskatchewan, grasshopper population densities are particularly high in the southern and central regions. Ripening canola crops are currently playing host to crickets (reported consuming pods), crucifer flea beetles, diamondback moth and Lygus bugs. Densities of diamondback moth and Lyugs have been economically significant in some regions, so scouting is important. Pea aphid and cereal aphid numbers appear to be increasing in some parts of the province, so scouting for these pests in their respective host crops is also important as the growing season winds down. There have been four reports of Hessian fly in Saskatchewan this summer.

Saskatchewan Crop Production News issues are now online! There are links on the Crop Production News page so that interested readers can subscribe to the newsletter or read issues from past years.

A diamondback moth larva on a canola leaf. Population densities are high in some fields and scouting is needed to avoid unpleasant surprises. Picture by Jonathon Williams, AAFC-Saskatoon.

In Manitoba, aphid population densities have been high enough to warrant control in small grain cereal crops in some regions, especially where crops were planted late and crops are still in vulnerable stages. Where there are a lot of aphids in fields, there have also been lots of lady beetle larvae and aphid mummies (resulting from aphids being attacked by parasitoids). A few fields in the Cypress River/Balder area of Manitoba have been sprayed for bertha armyworm. Some canola fields have been sprayed for diamondback moth and Lygus bugs in the Eastern region, and for diamondback moth in the Interlake region. Like in Saskatchewan, crucifer flea beetles are now active again, and are feeding on green canola.  A soybean field in the Central region of Manitoba was treated for spider mites. Some insecticide applications for banded sunflower moth have occurred in the Eastern region. Grasshoppers are numerous in crops in some areas, and pastures in some areas have been sprayed for grasshoppers. John spotted some dead grasshoppers clinging to the upper leaves of plants that were infected with the pathogen Entomophaga grylii, but the incidence of infection has been low so far this year. Scout for aphids in cereal crops and for a variety of insects in canola fields.

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).

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Prairie Research

Boyd Mori, Kanishka Seneveirathna, Natalie LaForest and Meghan Vankosky
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Week 13

*This text was prepared by Kanishka Seneveirathna, Natalie LaForest, and Boyd Mori from the University of Alberta

Under the supervision of Dr. Boyd Mori at the University of Alberta, the ecological and agricultural entomology lab employs diverse molecular methods to tackle pest-related problems and develop integrated pest management approaches. Here we highlight research conducted by two graduate students: Kanishka Seneveirathna and Natalie LaForest.

Kanishka’s research uses population genetics to detect and monitor invasive insects in the prairie ecosystem. His research focuses on reconstructing the invasion routes of wheat midge (Sitodiplosis mosellana) and diamondback moth (Plutella xylostella), two devastating pests, by determining their origins in North America. To understand their invasion patterns, Kanishka employs a genomic approach (RADSeq), which allows for genome-wide population structure analysis.

A pheromone trap (left) used to collect adult wheat midge for population genetic analyses. The adult midge are trapped on a sticky card (right). Pictures by Kanishka Seneveirathna, University of Alberta.

By reconstructing the invasion routes of these pests, Kanishka aims to identify their origins and determine the genetic diversity and structure of different populations. This comprehensive understanding will facilitate the development of integrated pest management strategies, including forecasting systems and insecticide resistance management strategies. Initial findings indicate multiple independent invasion events for wheat midge across North America.

Moving forward, Kanishka and the Mori Lab team will work with members of the PPMN to collect a larger number of samples across the Prairies, ensuring comprehensive coverage. Collaboration with international research groups is also on the agenda, enabling the validation of findings and broader knowledge exchange. The goal is to develop effective management strategies to mitigate the damage caused by these invasive pests and enhance the productivity and quality of canola and wheat crops in the Canadian Prairies.

Pheromone traps (A) are used to collect adult diamondback moths in canola fields. Once trapped, the moths are removed from the sticky cards that are placed on the floor of the pheromone trap (B). To collect diamondback moth larvae for population genetic analyses, canola is sampled using sweep nets (C). Pictures by Kanishka Seneveirathna, University of Alberta.

Natalie’s research focuses on integrated pest management, more specifically the ecosystem service of weed seed predation performed by ground beetles (Coleoptera: Carabidae). Previous research on determining the species of weeds consumed by this group of beneficial insects have used seed cards in the field or cafeteria choice tests in the laboratory. Natalie’s work uses a multiplex-PCR approach, where she uses the DNA found within the gut of field captured ground beetles to determine what the ground beetles are consuming in the field. She is designing species-specific primers of agronomic significant weeds to decipher this significant predator-prey interaction. 

Throughout the 2021 and 2022 seasons, the most abundant ground beetle species collected has been Pterostichus melanarius, which is an introduced, opportunist generalist predator. Natalie is focusing on ground beetles in wheat and industrial hemp, but there are other members in the Mori lab looking at the prey items of ground beetles in canola and pulses. Identifying species specific predator-prey interactions will development more sustainable pest management strategies for producers.

A pitfall trap full of adult ground beetles (Coleoptera: Carabidae); pitfall traps are used to collect ground beetles and other insects during the growing season. Picture by Natalie LaForest, University of Alberta.
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Pre-Harvest Intervals (PHI)

Meghan Vankosky and Jennifer Otani
Categories
Week 13

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.

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

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English Grain Aphid

Shelby Dufton, Amanda Jorgensen, Jennifer Otani and Meghan Vankosky
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Week 13

The English grain aphid (Sitobion avenae) is a pest that infests wheat, barley, oat, rye, timothy, and canaryseed. Adults are 1.5 to 2 mm in size and yellow-green to reddish-brown with black antennae, leg joints, and cornicles. Nymphs are similar in appearance, but smaller in size. 

Adults and nymphs of the English grain aphid. Picture credit: Jennifer Otani, AAFC-Beaverlodge.

Aphids are typically found on the heads of cereal crops, where they feed on the ripening kernels. Feeding damage results in shriveled kernels and leaf discoloration. Severe infestations result in large visible bronze or brown patches in the field. English grain aphids produce honeydew, a sugary liquid waste, that can promote the infestation and growth of saprophytic and pathogenic fungi on cereal heads. This aphid is also a vector for barley dwarf virus, which can severely stunt plants and prevent heading. 

English grain aphids on a cereal head. Picture credit: Jennifer Otani, AAFC-Beaverlodge.

The economic threshold for English grain aphids in spring wheat in western Canada is 12-15 aphids per head prior to the soft dough stage. The number of aphids per head should be recorded on 20 tillers at five different spots scattered throughout the field to ensure an accurate estimate of their population density. Scouting should occur from June until the soft-dough stage is reached. Early seeding may allow crops to move past susceptible stages before aphid populations reach damaging thresholds and reduce risk for barley yellow dwarf virus.  

More information related to English grain aphid and other aphid species can be found on provincial the Manitoba Agriculture page. For more information, check out the English grain aphid page in the Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management field guide. (en français : Guide d’identification des ravageurs des grandes cultures et des cultures fourragères et de leurs ennemis naturels et mesures de lutte applicables à l’Ouest canadien).  

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