2023 Week 3 (Released May 25, 2023)

It’s already Week 3!

The week of May 22-26 saw the arrival of some much needed precipitation to parts of Alberta and Saskatchewan, but hot weather up to May 21 across most of the prairies has affected insect development so far this spring.

Grasshoppers thrive in warm, dry conditions and we continue to hear about high numbers of nymphs along roadsides and field edges. Diamondback moths have been captured in pheromone traps across the prairies, generally in low numbers. In preparation for bertha armyworm monitoring, we ran the model for pupal development this week and unsurprisingly, development is ahead of schedule. For more information, check out the posts in the Weekly Update! The Insect of the Week is about parasitoids of cutworms this week – read on and check out the links for more information. Finally, Dr. Kevin Floate has written a new book about dung beetles that is available for free download!

The prairie-wide maps summarizing the results from the 2022 growing season are online and available for review, as are the historical insect pest distribution maps. These prairie-wide geospatial maps offer insight into potential risk and help growers prioritize their scouting lists.

Remember, insect Monitoring Protocols containing helpful insect pest biology, how and when to plan for in-field scouting, and even thresholds to help support in-field management decisions are all available for review or download.

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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.

Weather Synopsis

***Special thanks to Mark Berry, AAFC-Geomatics, for providing up-to-date weather information for the prairies that is summarized here and used to predict insect development. Mark provides this information for every Weekly Update, but I’m new to running the website and have not yet figured out how to add him to the author list for the posts***

During the week of May 15-21 average prairie temperatures continued to be well above average. The average daily temperature was 4°C warmer than normal (Fig. 1). The warmest temperatures were observed across Alberta and western Saskatchewan. Dawson Creek, BC was 8°C warmer than average temperatures for mid-May. The coolest weekly temperatures were observed over eastern Saskatchewan and Manitoba.

Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of May 15-21, 2023.

Average temperatures over the past 30 days (April 22 – May 21, 2023) have been 3°C above normal with the warmest values being reported for Alberta and western Saskatchewan (Fig. 2).

Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of April 22-May 21, 2023. 

Since April 1, the 2023 growing season has been coolest across eastern Saskatchewan and Manitoba (Fig. 3). Alberta temperatures continue to be above average. Relative to climate normals, growing season temperatures have been well above normal in the Peace River region. Fort Vermillion, AB has been 5°C warmer than normal and Fort St. John, BC has been 4°C above normal. Temperatures have been below normal for many locations in Manitoba. For example, the average temperature near Melita has been 2.25°C cooler than average. 

Figure 3. Growing season average temperature (°C) observed across the Canadian prairies for the period of April 1 to May 21, 2023. 

Seven-day cumulative rainfall (May 15-21) was very low for Alberta and Saskatchewan (Fig. 4). Over the past 30 days (April 22 – May 21, 2023), rainfall has been minimal for Saskatchewan and Alberta (Fig. 5). For example, Saskatoon has had 12 mm of rain in that time, which is only 9% of what the Saskatoon area normally receives in the same period. On average, the prairie region has received about 40% of the precipitation normally expected for this time of year. For more information, visit the Agriculture and Agri-Food Canada Agroclimate site (https://www.agr.gc.ca/DW-GS/current-actuelles.jspx?lang=eng&jsEnabled=true).

Figure 4. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of May 15-21, 2023. 

Figure 5. 30-day average cumulative rainfall (mm) observed across the Canadian prairies for the period of April 22-May 21, 2023. 

Growing season rainfall has been below normal across most of the prairies so far in 2023 (Fig. 6). A large region, extending from Lethbridge to Saskatoon to the Peace River region continues to have well below normal rainfall accumulations (Fig. 6). Meadow Lake rainfall has been 34% of normal and Kindersley has reported only 15 mm (42% of normal). 

Figure 6. Growing season cumulative rainfall (mm) observed across the Canadian prairies for the period of April 1 to May 21, 2023. 

Wind trajectory summary

Agriculture and Agri-Food Canada (AAFC; Ross Weiss, Meghan Vankosky) and Environment and Climate Change Canada (ECCC; Serge Trudel) have been working together to study the potential of trajectories for monitoring insect movements since the late 1990s. Trajectory models are used to deliver an early-warning system for the origin and destination of migratory invasive species, such as diamondback moth. 

‘Reverse trajectories’ refer to air currents that are tracked back in time from specified Canadian locations over a five-day period prior to their arrival date.  Of particular interest are those trajectories that, prior to their arrival in Canada, originated over northwestern and southern USA and Mexico, anywhere diamondback moth populations overwinter and adults are actively migrating.  If diamondback moth adults are present in the air currents that originate from these southern locations, the moths may be deposited on the Prairies at sites along the trajectory, depending on the local weather conditions at the time that the trajectories pass over our area (e.g., rain showers, etc.). Reverse trajectories are the best available estimate of the ”true” 3D wind fields at a specific point. They are based on observations, satellite and radiosonde data. 

Wind Trajectories, May 1 to May 23, 2023:

Since May 1, 2023, the majority of reverse trajectories that have crossed the prairies originated from the Pacific Northwest (Idaho, Oregon and Washington) (Fig. 1). Very few reverse trajectories that originated in Mexico, California or Texas passed over the Canadian prairies between May 1 and May 23. No reverse trajectories, originating over Oklahoma or Texas crossed over the prairies this week. 

Figure 1. The average number (based on a 5-day running average) of reverse trajectories (RT) that have crossed the prairies for the period of May 1-23, 2023. 

The majority of reverse trajectories originating in the Pacific Northwest have been reported to pass over south-central Alberta and southwestern Saskatchewan (Fig. 2).  

Figure 2. Total number of dates with reverse trajectories originating over the Idaho, Oregon, and Washington that have crossed the prairies between April 1 and May 23, 2023. 

Since April 1, reverse trajectories that originated in Kansas and Nebraska were reported to cross southeastern Saskatchewan and southern Manitoba (Fig. 3).

Figure 3. The total number of dates with reverse trajectories originating over Kansas and Nebraska that have crossed the prairies between May 1 and May 23, 2023. 

Predicted grasshopper development

Model simulations were used to estimate development of grasshoppers as of May 21, 2023. Compared with average spring temperatures, well above normal temperatures in Alberta and western Saskatchewan have contributed to rapid grasshopper egg development (Fig. 1) that is well ahead of what we would expect at this time in an average growing season (Fig. 2). Average egg development for the prairies is 81% complete. The model predicts that egg development is well ahead of the long-term value of 67% complete for this time of year. Cool conditions in Manitoba have resulted in slower development rates that are similar to long-term average development rates.

Figure 1. Predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 21, 2023.  

Figure 2. Long-term average predicted grasshopper (Melanoplus sanguinipes) embryological development across the Canadian prairies as of May 21, based on climate normals data.  

As a result of above normal temperatures, model predictions indicate that grasshopper eggs have already started to hatch, especially in Alberta and western Saskatchewan (Fig. 3). Model simulations suggest that hatch rates are 15-35% across the Peace River region. This is well ahead of long-term average hatch rates and we already have reports of grasshopper nymphs found along roadsides and field edges in Alberta and Saskatchewan. Prairie farmers should be prepared to scout for grasshoppers for the next 2-3 weeks, especially if conditions remain warmer and drier than normal. 

Figure 3. Predicted grasshopper (Melanoplus sanguinipes) hatch (%) across the Canadian prairies as of May 21, 2023. 

Predicted diamondback moth development

Analysis of wind trajectory data (from Environment and Climate Change Canada) indicates that a number of upper air currents, originating over the USA Pacific Northwest, passed over Alberta and Saskatchewan during the last week of April and first three weeks of May. These wind currents could have been carrying adult diamondback moths into the prairies. In fact, adult diamondback moths have been collected in traps located across Alberta (information courtesy of Shelley Barkley, Alberta Agriculture and Irrigation) and Saskatchewan (information courtesy of Carter Peru and James Tansey, Saskatchewan Ministry of Agriculture) during the first three weeks of May.

DBM development can be rapid during periods of warm weather. This week, the diamondback moth model was initialized for May 1, 2023 and run to May 21. Though canola may not be present, model results indicate that females may have begun to lay eggs on cruciferous plants like volunteer canola and weeds. Larvae could now also be found feeding on these host plants. The model simulation indicates that populations near Grande Prairie, AB (Fig. 1) are likely to be more advanced in terms of development than populations near Cadillac, SK (Fig. 2) reflecting differences in growing season weather so far in 2023 at the two locations. 

Figure 1. Predicted development of diamondback moth (Plutella xylostella) near Grande Prairie, AB as of May 21, 2023. 

Figure 2. Predicted development of diamondback moth (Plutella xylostella) near Cadillac, SK as of May 21, 2023 (Biofix date = May 1, 2023). 

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 male diamondback moth counts will be available for each province as the monitoring season progresses. 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 dislodged from the plant. Repeat this procedure at least in five locations in the field to get an accurate count.

The life stages of diamondback moth, Plutella xylostella: (A) eggs, (B) early instar larva, (C) late instar larvae, (D) pupa, and (E) adult moth. Photo credit: Jonathon Williams, AAFC-Saskatoon (all pictures)

Biological and monitoring information for DBM (including tips for scouting and economic thresholds) is posted by Manitoba AgricultureSaskatchewan Ministry of 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 Field Guides page.

Predicted bertha armyworm development

Based on model simulations, development of overwintered BAW pupae this spring (Fig. 1) is expected to be significantly ahead of normal for most of the prairies (Fig. 2). BAW pupal development in Alberta is 10-14 days faster than average development for this time of year.

Figure 1. Predicted bertha armyworm (Mamestra configurata) pupal development (%) across the Canadian prairies as of May 21, 2023. 

Figure 2. Long-term average predicted bertha armyworm (Mamestra configurata) pupal development (%) across the Canadian prairies as of May 21, 2023. 

To best detect the initial flight of adult BAW, pheromone traps should be placed in fields when pupal development is 75-80% complete. This ensures that traps are deployed before adults emerge and the mating period begins. Based on current BAW development, as predicted by the model, it is advisable that pheromone traps in Alberta be placed in fields this week or early next week (week of May 29). Pheromone traps should be installed later next week in most of Saskatchewan. At trap sites in eastern Saskatchewan and Manitoba, the pheromone traps should be placed in fields before June 9th

Refer to the PPMN Bertha armyworm monitoring protocol for help when performing in-field scouting for adult moths and for larvae.

Provincial Insect Updates

Provincial entomologists provide insect pest updates throughout the growing season. Visit the links below to read their updates and to find other valuable information about prairie crop insects and beneficial insects.

The first Manitoba Crop Pest Update for 2023 is now available! Looking for historical information? Links are available for past Updates too.

Watch for new issues of the Saskatchewan Crop Production News coming soon in 2023 and browse the articles from 2022 for information from the past.

Visit the Alberta Insect Pest Monitoring Network page for information about insect monitoring in Alberta, including live maps from the 2023 monitoring season for diamondback moth, bertha armyworm, cutworms and others.

NEW BOOK! Cow patty critters: An introduction to the ecology, biology and identification of insects in cattle dung on Canadian pastures

Entomologist Dr. Kevin Floate aims to answer ‘what critters are found in a cow patty?’ and ‘what do they do?’ His hope is to spark the interest of ranchers and farmers, and to stir the minds of students studying insects. In his own words, ‘This is the guide I wish I had when I started my career.’

Cover and sample content of Cow Patty Critters

Insects serve an outsized role in many ecosystem services. For dung on Canadian pastures, there are over 300 species of insects helping to break down and cycle nutrients through the soil and food webs. Understanding what insects are present in a cow patty provides insights into livestock health and ecological processes.

Dr. Kevin Floate speaking about insects to a captivated audience. Photo credit: Cam Goater, University of Lethbridge

Download your copy of Cow Patty Critters in English or in French.

This new 224-page, full color guide provides the ‘doorway’ to learn more about the critters one can find in cow dung: how to identify them, how they can be beneficial, and additional information on the biology and morphology of multiple insect groups. Also included is an extensive reference list for those who wish to pursue detailed insect identification.


While you’re out scouting for cutworms, tachinids flies and ichneumonid wasps are scouting for them too! We have two Insects of the Week this week and both are parasitoids of cutworm pests. Parasitoids complete part of their lifecycle inside another organism, in this case cutworms, eventually killing them.  

Adult tachinid flies are pale or dark brown in colour with long, bristly hairs covering their bodies. Females typically lay one to several eggs on a host. Upon hatching the larvae burrow into the host, develop inside, and then exit to pupate in the soil. Adult flies feed on flower nectar, honeydew from aphids, scale insects, and mealybugs. The tachinid, Athrycia cinerea (Coq.), is a parasitoid of the Bertha armyworm.  

An adult tachinid fly (Tachinia algens) reared from glassy cutworm. Photo credit: Shelby Dufton, AAFC-Beaverlodge Research Farm.

Ichneumonidae adults vary in size and colouration but all have a narrow waist, a long abdomen, and long antennae. Females have long ovipositors that they use to inject eggs into their hosts, including cutworm larvae. Adults eat nectar and aphid honeydew. Ichneumonid larvae (including Banchus flavescens) are parasitoids of Lepidoptera, Coleoptera, Diptera, Hymenoptera, and some spiders.  

An adult Ichneumonid parasitoid of the genus Banchus, reared from a dingy cutworm. Photo credit: Shelby Dufton, AAFC-Beaverlodge Research Farm.

For more information about these parasitoids, the other pests they control and other important crop and forage insects, see the Field Crop and Forage Pests and their Natural Enemies in Western Canada guide. The guide has helpful information about the life cycle of these and other parasitoids. The guide also has tips for conserving parasitoids and pictures to help with identification.