2023 WEEK 10 (Released July 12, 2023)

Meghan Vankosky
Week 10

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 in May and June.

Adult grasshoppers are becoming more common across the prairies now. Although grasshoppers are more widespread this year than in the past few years, the stage of grasshopper development and grasshopper population densities can vary between even relatively close locations. Scouting individual fields is important to best estimate crop risk.

The first adult wheat midge of 2023 were reported in Saskatchewan in late June. Adult flight may have peaked in some areas, but scouting remains important in wetter areas of the prairies.

Diamondback moth could be entering into the third non-migrant generation in some areas this week (if present). Check back next week for a more in-depth update on diamondback moth development but keep in mind that diamondback moth develop quickly in warm weather which could lead to rapidly increasing populations over the summer. Use the links in the Provincial Insect Updates post to learn about diamondback moth and bertha armyworm risk in your region and scout accordingly.

There is now a monitoring protocol for canola flower midge! As canola flowering finishes, it can be easy to see the galled flowers that result from infestation by canola flower midge, so the time to scout could be now or coming soon. A three-year survey completed in 2019 found that canola flower midge is quite widely distributed across the prairies, but in relatively low densities and probably doesn’t cause economic yield losses. If you scout for canola flower midge this year and are willing to share your results please send them to meghan.vankosky@agr.gc.ca. If we get enough information, we will map the results!

This is a busy time for our field research programs across western Canada and with upcoming field days, we are even busier. A list of events can be found on the Prairie Pest Monitoring Network homepage and in this weekly update. Read about the AAFC display planned for Ag in Motion in the latest edition of Science News from the Prairies – find a link to the newsletter in the Prairie Research post where we also feature a new research project focused on the lesser clover leaf weevil.

This week, the Insect of the Week featured Macroglenes penetrans, a parasitoid that attacks wheat midge. Diamondback moth is on our schedule for next week!

Remember, insect Monitoring Protocols containing information about in-field scouting as well as information about insect pest biology and identification.

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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

Ross Weiss, Tamara Rounce, Jennifer Otani and Meghan Vankosky
Week 10

During the week of July 3-9, 2023, the warmest weekly average temperatures occurred across most of the Peace River region, southern Alberta and southwestern Saskatchewan (Fig. 1). The coolest temperatures during the same week occurred across the Parkland region of Manitoba and Saskatchewan. The prairie average daily temperature was similar to that expected based on climate normals. In fact, a number of locations reported temperatures that were cooler than normal; in northeastern Saskatchewan, for example, some locations had weekly average temperatures that were 2°C cooler than normal.

Figure 1. Seven-day average temperature (°C) observed across the Canadian prairies for the period of July 3-9, 2023. 

Average temperatures over the past 30 days (June 10 – July 9, 2023) have been almost 2°C above normal; many locations in the Peace River region have reported 30 day average temperatures that were 3°C warmer than average. The warmest 30-day average temperatures were reported across most of the southern prairies, particularly southern Manitoba (Fig. 2).

Figure 2. 30-day average temperature (°C) across the Canadian prairies for the period of June 10 to July 9, 2023. 

Precipitation for the period of July 3-10, 2023 was minimal across most of the prairies (Fig. 3).

Figure 3. Seven-day cumulative rainfall (mm) observed across the Canadian prairies for the period of July 3-9, 2023. 

Cumulative rainfall for the past 30 days has been greatest in the Edmonton region (Fig. 4). The lowest rainfall amounts continue to be those reported across most of Saskatchewan and southern Alberta. Conditions continue to be dry across most of the prairies.

Figure 4. 30-day cumulative rainfall (mm) observed across the Canadian prairies for the period of June 10 to July 9, 2023. 

Prairie rain amounts for June 10-July 9 have been 72% of normal on average across the prairies. Most of Saskatchewan has had less than 40% of normal rainfall (Fig. 5). Southern Alberta and most of Manitoba have had rainfall amounts that are less 60% of normal (Fig. 5). 

Figure 5. The percent of normal precipitation (based on cumulative rainfall, in mm) over the last 30 days (June 10 to July 9, 2023) observed across the Canadian prairies.

Predicted Grasshopper Development

Ross Weiss, Tamara Rounce, Owen Olfert, Jennifer Otani and Meghan Vankosky
Week 10

Model simulations were used to estimate the status of grasshopper development as of July 9, 2023. As a result of warmer than normal temperatures, grasshopper development continues to be well ahead of average. As of July 9. 2023, the average predicted instar for grasshopper populations across the prairies is 4.9, which is significantly greater than the long term average of 3.1 for this time of year. Simulations indicate that 70% of the prairie population should be in the fifth instar or adult stage (Fig. 1).

Figure 1. Predicted grasshopper (Melanoplus sanguinipes) development, presented as average instar, across the Canadian prairies as of July 9, 2023. 

In a ‘normal’ year, we would expect that 57% of the grasshopper population would be in the third or fourth instar in early July (Fig. 2).

Figure 2. In an average year (based on 30-year average weather or climate normals), we expect that about 57% of the grasshopper population would be in the third or fourth instar in early July, as pictured here on the map. In contrast, in 2023, warm weather has significantly sped up the rate of grasshopper development (Fig. 1). 

Reports from across the prairies indicate that adult grasshoppers are now occurring. This is much earlier than normal, but agrees with our model simulations, which predict that adult grasshoppers are now occurring across most of the prairies (Fig. 3). Based on earlier than normal appearance of adults, high densities and drought conditions, grasshopper risk may be significant for large areas of Alberta and Saskatchewan as well as southern Manitoba. 

Figure 3. The proportion (%) of the migratory grasshopper (Melanoplus sanguinipes) population expected to be in the adult stage across the Canadian prairies as of July 9, 2023. 

Models and geospatial maps are tools to help time in-field scouting on a regional scale but grasshopper development and population densities can vary even between relatively close locations. Thus, grasshopper populations are best assessed through scouting. Monitor roadsides and field margins to assess the developmental stage and densities of local grasshopper populations.  

Information about grasshoppers and grasshopper monitoring is available from the Prairie Pest Monitoring NetworkAlberta Agriculture and IrrigationSaskatchewan Ministry of Agriculture, and Manitoba Agriculture and in the Field Crop and Forage Pests guide.


Predicted Wheat Midge Development

Ross Weiss, Tamara Rounce, Owen Olfert, Jennifer Otani and Meghan Vankosky
Week 10

Wheat midge (Sitodiplosis mosellana) emergence is limited when soil moisture is lacking. Dry conditions in southcentral Manitoba as well as central and southern regions of Alberta have likely resulted in reduced emergence of larvae from the soil. The wheat midge development model indicates that peak emergence of adults is now occurring. Oviposition is predicted to have begun across most of the prairies and eggs should be the most abundant lifestage (Fig. 1).

Figure 1. Percent of the wheat midge (Sitodiplosis mosellana) population that is predicted to be in the egg stage in western Canada, as of July 9, 2023. Note that wheat midge may not be active in all parts of the prairies, for example in regions where populations were absent last year or in regions where it did not rain in May and June.

In fields across Saskatchewan and western Manitoba, if wheat midge are present, model simulations indicate that egg development is progressing and larvae should be present (Fig. 2).

Figure 2. Percent of the wheat midge (Sitodiplosis mosellana) population that is predicted to be in the larval stage (in wheat heads) in western Canada, as of July 9, 2023. 

The wheat midge model, run for Regina, Saskatchewan indicates that adult emergence has peaked (Fig. 3) in that area. Oviposition should peak later this week. Larval populations (in wheat heads) should reach peak populations later next week.  

Figure 3. Predicted development of wheat midge (Sitodiplosis mosellana) near Regina, Saskatchewan as of July 9, 2023. 

Based on the occurrence of wheat midge adults, field monitoring should begin now, if it has not started already. In order to assess wheat midge populations and to take the appropriate action for management, it is recommended that fields should be monitored when wheat is between heading and flowering. Field inspection should be carried out after 8:30 p.m. when the female midge are most active. Females are more active when the temperature is above 15°C and wind speed is less than 10 km/h. Wheat midge populations can be estimated by counting the number of adults present on four or five wheat heads. 

For more information about scouting and economic thresholds, check out the wheat midge monitoring protocol and the Insect of the Week for Week 8, that featured wheat midge. More information is available from Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, and Field Crop and Forage Pests and their Natural Enemies in Western Canada available for free download from our Field Guides page.


Canola Flower Midge Scouting

Meghan Vankosky and Boyd Mori
Week 10

Scouting for canola flower midge tends to be easiest as the flowering stage of canola ends and pod development begins. Female canola flower midge lay eggs on developing canola buds and larvae develop inside the buds, resulting in galled flowers that do not open or produce pods.

A canola raceme with galled flowers containing canola flower midge larvae; these galled flowers will not produce pods. Picture credit: Boyd Mori, University of Alberta.

From 2017-2019, entomologists and volunteers across the prairies conducted a survey to determine the range of canola flower midge (Fig. 1). There has not been a formal survey conducted since 2019.

Figure 1. Density of canola flower midge, based on the number of galled flowers per raceme across the prairie region observed during a survey conducted in 2017, 2018, and 2019. Map credit: Shane Hladun; map modified from Vankosky et al. (2022).

Although canola flower midge does not appear to occur at densities that cause economic damage, scouting for canola flower midge will help to monitor population growth at the local scale to avoid surprises in the future. The monitoring protocol used from 2017-2019 is now available online so that everyone can scout for canola flower midge.

*If you cannot follow the link to the protocol, please contact Dr. Meghan Vankosky (meghan.vankosky@agr.gc.ca).


Upcoming Events

Meghan Vankosky
Week 10

Several field days are coming up! Entomologists, weed scientists, and plant pathologists from across western Canada will be attending various events over the next few weeks. Please look for us – we love to talk about insects, weeds, and plant diseases! A partial list of upcoming events (in no particular order and with no endorsement intended) includes:

Ag in Motion, July 18-20, 2023 at Langham, Saskatchewan.

2023 Lacombe Field Day, July 26, 2023 from 8:00 am to 4:30 pm MDT. Use this link to register.

Saskatchewan Crop Diagnostic School, July 25 or July 26, 2023 at Indian Head, Saskatchewan. It looks like registration for July 25 is maxed out, but spots are still available on July 26.

North Peace Applied Research Association Tour on July 27, 2023 in the Peace River region.


Prairie Research

Jeremy Irvine, Sean Prager and Meghan Vankosky
Week 10

Science News from the Prairies

A new issue of the newsletter, Science News from the Prairies is now available! This issue highlights the Agriculture and Agri-Food Canada information booth that can be found at Ag in Motion (July 18-20, 2023), new publications arising from prairie research, and upcoming events.

Developing Economic Thresholds for Lesser Clover Leaf Weevil

*This text was prepared by Jeremy Irvine and Sean Prager from the University of Saskatchewan.

Red clover (Trifolium pratense) is a short-lived perennial crop grown for seed production. Red clover seed is an important commodity in the Canadian Prairies, providing upwards of $2 million annually to the Saskatchewan economy. The production of red clover seed can be affected by the lesser clover leaf weevil (Hypera nigrirostris; LCLW). Yield losses of up to 50% have been recorded with high infestations of the LCLW. The weevil larvae feed on the developing shoots, flower heads, and seeds of red clover plants. Larvae cause the worst damage but secondary feeding damage can occur once LCLW larvae become adults.

Lesser clover leaf weevil damage, resulting when larvae exit the stem of the host plant. Picture credit: Jeremy Irvine, University of Saskatchewan.

Lesser clover leaf weevils are traditionally controlled using insecticides, but these can have negative impacts on  non-target insect species, notably bees. Managed bee species are used by red clover seed growers to ensure fields receive adequate pollination, high seed set, and subsequent yield.

There are currently no established economic thresholds for control of LCLW and insecticides can be applied when they are not needed, which increases the cost of clover production, negatively affects pollinators, and could contribute to the development of insecticide resistance in the LCLW population. The threat of insecticide resistance is significant because there is only one registered active ingredient for LCLW.  

A field trial near Carrot River, Saskatchewan is set up in second-year red clover to study the lesser clover leaf weevil. Picture by Jeremy Irvine, University of Saskatchewan.

The primary purpose of this research, which began in May 2023, is to develop an economic thresholds for LCLW in red clover crops. The project will also study the development of LCLW in varying weather conditions so that seasonal development can be incorporated into the economic thresholds. Finally, the project will generate a sequential sampling plan, meant to assist with the decision-making process to optimize management of LCLW. To conduct this research, we will work with farmers to conduct on-farm field trials where LCLW population densities will be manipulated and red clover yield will be quantified to determine the relationship between weevil density, injury level, and yield loss.

The overall goal of our project is to develop new tools that can be used to manage LCLW and protect red clover seed yields. Financial support for this study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC), the Government of Saskatchewan Agriculture Development Fund (ADF) and the Saskatchewan Forage Seed Development Commission (SFSDC).


Provincial Insect Updates

Meghan Vankosky
Week 10

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.

Saskatchewan Crop Production News issues are now online! Use this link to read Issue #2 and watch for future issues. Issue #2 for 2023 includes information plant diseases and plant staging for pesticide applications. There are links on the Crop Production News page so that interested readers can subscribe to the newsletter.

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).



Amanda Jorgensen, Shelby Dufton, Jennifer Otani and Meghan Vankosky
Week 10

Macroglenes penetrans is a beneficial parasitoid wasp from the family Pteromalidae. It is an important natural enemy of wheat midge. This small, black wasp can be seen emerging in large numbers from wheat stubble shortly after wheat midge adults are first sighted. This means that often they are emerging into canola fields and then have to disperse to find wheat fields where their hosts are active. Macroglenes penetrans is a parasitoid that lives inside the wheat midge larva and overwinters within the wheat midge larval cocoon. In the spring, the parasitoid larva develops to emerge from the wheat midge cocoon buried in the soil and then the adult parasitoid seeks out wheat midge eggs. 

A very small adult Macroglenes penetrans on a wheat head. Picture credit: Shelby Dufton, AAFC Beaverlodge Research Farm.

Macroglenes penetrans is an important part of wheat midge management – parasitism rates can reach upwards of 70% of the wheat midge population! The numbers of this parasitoid overwintering inside wheat midge cocoons are counted during the fall soil core survey, so that the survey map only includes counts of non-parasitized wheat midge.  

Biological and monitoring information related to Macroglenes penetrans and the wheat midge in field crops can be found 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).