Prairie Pest Monitoring Network: Results of 2022 Surveys and Monitoring

In 2022, collaborators and contributors of the Prairie Pest Monitoring Network conducted surveys and monitoring for grasshoppers, bertha armyworm, wheat midge, wheat stem sawfly, pea leaf weevil, cabbage seedpod weevil, and diamondback moths. Over 5000 samples were collected (Figure 1) and we acknowledge the considerable and valuable contribution that all of our collaborators and volunteers made in 2022. We also thank the organizations that fund the Prairie Pest monitoring network and recognize the considerable in-kind contributions made by our provincial partners, including Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, and Manitoba Agriculture. Thank you to everyone!

To volunteer access to your farmland for insect, plant pathogen and disease surveys in Saskatchewan in 2023, please visit the Pest Monitoring In Saskatchewan Page.

Figure 1. Distribution of sampling points from the 2022 survey season.

Bertha armyworm

Meghan Vankosky, Owen Olfert, John Gavloski, Shelley Barkley, James Tansey, Ross Weiss, Jennifer Otani

Bertha armyworm (Mamestra configurata) populations are monitored annually in western Canada using pheromone baited traps. These traps are maintained by volunteer growers and agronomists, and by provincial and federal entomologists. The protocol used to monitor bertha armyworm using pheromone traps was updated in spring 2019 and is available here. The monitoring program provides early warning of when regional population densities may be approaching economic thresholds. However, site-specific interpretation of trap counts is difficult because pheromone traps do not capture female moths and it is the females that decide where to lay eggs. In-field scouting for bertha armyworm larvae is required for accurate, local, population estimates, as described in the monitoring protocol.

Cumulative trap captures below 600 generally represent low risk to crop production. In 2022, the cumulative trap captures of male bertha armyworm were very low, with very few traps across the prairies capturing more than 300 moths (Figure 2). The monitoring results from 2022 were very similar to those from 2020 and 2021 (Figure 3).

Figure 2. The cumulative trap catch of adult male bertha armyworm (Mamestra configurata) in pheromone-baited traps across the prairies in 2022 (map by Ross Weiss, AAFC-Saskatoon).

Figure 3. The cumulative trap catch of adult male bertha armyworm (Mamestra configurata) in pheromone-baited traps across the prairies from 2018 to 2021 (maps by David Giffen, AAFC-Saskatoon).

This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers. The network of pheromone traps was implemented and monitored by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC).

Grasshoppers

Meghan Vankosky, Owen Olfert, James Tansey, John Gavloski, Shelley Barkley, Ross Weiss, Jennifer Otani

The grasshopper survey is conducted by estimating adult grasshopper densities in the late summer and early fall, usually in ditches alongside cereal fields. This survey estimates the number of adult grasshoppers capable of laying eggs before winter and contributes to an estimate of future risk, where high densities in the current year predict higher levels of risk to crops in the next growing season. However, weather and biotic factors may increase or reduce risk during a given growing season, and these are not incorporated into the map in Figure 4. Factors that lead to increased grasshopper populations include warm and dry conditions in late summer and fall; these encourage mating, egg laying, and egg development. Warm and dry conditions in the spring increase the survival of grasshopper hatchlings and the risk of crop damage. Cool and wet growing conditions have negative effects on grasshopper development. Therefore, actual levels of infestation in field crops may differ from those predicted by the fall survey because of regional variation in weather conditions and the grasshopper species present.

Recent dry conditions across the central and southern prairies have been ideal for grasshoppers. In 2022, grasshopper densities were greatest in the region south of the Yellowhead Highway corridor (Figure 4). Although the area with grasshopper infestation in 2022 was similar to that observed in 2021, population densities were greater in 2022 than in 2021. More widespread outbreaks were observed in 2022 (Figure 2) than in the last few years (Figure 5). Prairie farmers should be prepared to scout for grasshoppers in spring and early summer in 2023, especially if weather conditions remain warmer and drier than normal.

A protocol for grasshopper scouting is available on the Monitoring Protocol page.

Figure 4. Estimated grasshopper population densities in late summer and early fall 2022 in western Canada; areas with high grasshopper densities in 2022 are at risk of high grasshopper densities and associated damage in 2023, based on knowledge of the life history of the primary pest species, including Melanoplus sanguinipes (migratory grasshopper) (map by Ross Weiss, AAFC-Saskatoon).

Figure 5. Estimated grasshopper population densities from annual surveys conducted from 2018-2021 (maps by David Giffen, AAFC-Saskatoon).

This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse and Soybean Growers). The survey was implemented and conducted by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Saskatchewan Crop Insurance Corporation, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC).

Wheat midge

Meghan Vankosky, Owen Olfert, Shelley Barkley, James Tansey, Ross Weiss, Jennifer Otani

The risk of wheat midge (Sitodiplosis mosellana) infestation in 2023 was estimated based on the number of non-parasitized wheat midge larval cocoons in soil samples collected during the fall wheat midge survey conducted in 2022 (Figure 6). The forecast based on non-parasitized larvae provides a general picture of existing densities and the potential for damage in 2023. A number of other factors, in addition to parasitism, influence the overwintering and developmental success of larval wheat midge and might affect wheat midge adult emergence and risk of damage to wheat crops in 2023. Weather conditions (especially precipitation levels) in spring 2023, for example, will further influence the extent and timing of wheat midge emergence during the growing season. In spring 2023, the Prairie Pest Monitoring Network will use phenology models and weather conditions to model the expected emergence of wheat midge adults the Weekly Updates.

Wheat midge survey results and forecasts for previous years are shown in Figure 7.

All areas where wheat midge are active during the growing season are susceptible to crop damage because wheat midge larval feeding affects grain yield and quality. Growers in all areas where wheat midge have occurred in the past should monitor their fields during the susceptible crop stage (i.e., emergence of the wheat head from the boot until flowering) and when adult midge are active.

If adult midge density is equal to one midge per four or five wheat heads between emergence of the wheat heads and flowering (anthesis stage), insecticide application may be warranted. Please refer to provincial crop production guides for information about application and registered products. By the anthesis stage insecticides will not be cost effective as any larvae present will have already caused damage. Larvae that hatch from eggs laid late in or after the anthesis stage will not cause significant damage as the more mature wheat kernels are resistant to larval damage. Avoiding insecticide application after the anthesis stage will help protect populations of natural enemies in field crops, including parasitoids of wheat midge, and of other pests. Parasitism by a small parasitoid wasp (Macroglenes penetrans) can keep wheat midge populations from exceeding the economic threshold.

Figure 6. The densities of unparasitized wheat midge (Sitodiplosis mosellana) cocoons in soil samples collected in fall 2022 during the annual wheat midge survey. Risk of wheat midge infestation in 2023 is greatest in regions where wheat midge larval cocoon densities exceeded 600 midge/m2 during the fall 2022 survey, assuming sufficient rainfall in spring of 2023 (map by Ross Weiss, AAFC-Saskatoon).

Figure 7. The densities of unparasitized wheat midge used to forecast risk for the last four growing seasons (maps by David Giffen, AAFC-Saskatoon).

Surveys of wheat midge larval cocoons were conducted by Sharon Nowlan (SK) and by Alberta Agriculture and Irrigation. The survey was funded by Saskatchewan Crop Insurance Corporation, Saskatchewan Wheat Development Commission, and Alberta Agriculture and Irrigation. Prairie Pest Monitoring Network activity related to this survey was funded by the Canadian Agricultural Partnership.  

Cabbage seedpod weevil

Meghan Vankosky, Owen Olfert, Shelley Barkley, James Tansey, John Gavloski, Ross Weiss, Jennifer Otani

Populations of cabbage seedpod weevil (Ceutorhynchus obstrictus) were quite low north of Calgary in Alberta and Swift Current and Regina in Saskatchewan again in 2022 (Figure 8). In fact, population densities of cabbage seedpod weevil have been declining in Alberta and Saskatchewan over the last few years. In 2022, population densities were the lowest they have been since the first annual surveys were conducted in Alberta (early 2000s) and Saskatchewan (2007). The distribution and densities of cabbage seedpod weevil from 2018-2021 are shown in Figure 9.

No cabbage seedpod weevils were found in sweep samples collected in the Peace River Region of Alberta or British Columbia, but small numbers of weevils have been collected in north-central Alberta that could be source populations for the Peace River region.

In 2022, the greatest population densities were observed in southwestern Saskatchewan, from the AB/SK border to the Swift Current area (Figure 8). Some fields were sampled for cabbage seedpod weevil in Manitoba in 2022. Of those fields, some had weevils present in low numbers, including fields as far east as Carman (Figure 10). 

To protect crops from cabbage seedpod weevil damage, monitor canola and brown mustard fields on a regular basis from the bud stage until the end of flowering using the protocol available here. Accurate monitoring requires that sweep samples be collected from multiple locations within a field, with accuracy increasing as the sample size increases. To avoid overestimation of weevil populations, sweep samples should be taken from the interior of the field and not just from field edges. The nominal economic threshold for cabbage seedpod weevil is 2.5 to 4 adult weevils per sweep.

Figure 8. Cabbage seedpod weevil (Ceutorhynchus obstrictus) distribution in Saskatchewan and Alberta based on a sweep net survey conducted in randomly selected Brassica sp. fields in 2022 (map by Ross Weiss, AAFC-Saskatoon).

Figure 9. Density and distribution of cabbage seedpod weevil in 2018-2021 (maps by David Giffen, AAFC-Saskatoon).

Figure 10. Sampling points for the 2022 cabbage seedpod weevil, including fields in Manitoba, Canada, where cabbage seedpod weevils were collected in fields near Carman, MB (map by Ross Weiss, AAFC-Saskatoon).

Surveys were conducted by Alberta Agriculture and Irrigation, Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include Agriculture & Agri-Food Canada, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.

Wheat stem sawfly

Meghan Vankosky, Shelley Barkley, David Giffen, Owen Olfert, Jennifer Otani

Wheat stem sawfly (Cephus cinctus) was surveyed in southern Alberta in 2022 by counting the number of stems cut by wheat stem sawfly larvae along the edges of wheat fields (Figure 11). The 80 fields that were sampled had damage severity levels ranging from very low to high. Many of the fields sampled had at least 2-10% of stems cut (low damage severity); fields in the counties of Vulcan and Forty Mile had fields with high damage severity (>25% of stems cut). Fields in several counties, including Foothills, Willow Creek, Lethbridge, Warner, Wheatland, and Kneehill had 2-25% of stems cut by wheat stem sawfly in 2022, as did some fields around Oyen, Alberta (Figure 11). Although the areas with the highest population densities have shifted slightly between years (Figure 12), sawfly populations continued to increase in 2022 as compared to population densities observed between 2011 and 2017, with some notably high populations found farther north than normal in 2022. At present, wheat stem sawfly populations are not monitored in Saskatchewan. However, in 2022, there were some reports of sawfly damage from several fields across the province, including near Moosejaw, Pense, Biggar, and Cabri, in both spring wheat and durum crops.

Hot and dry weather conditions may contribute to decreased parasitism rates and sawfly population growth. Bracon cephi is the primary parasitoid of wheat stem sawfly. In hot and dry years, wheat plants mature early, limiting B. cephi to one generation and resulting in reduced parasitism rates. In normal growing seasons, B. cephi can have two generations per year and parasitism rates are higher, allowing B. cephi to exert more control over wheat stem sawfly populations. Very wet conditions can also hinder wheat stem sawfly population growth.

Figure 11. Wheat stem sawfly (Cephus cinctus) distribution in Alberta in 2022 based on results of a survey of cut stems in wheat fields counted after harvest (map by David Giffen, AAFC-Saskatoon).

Figure 12. Wheat stem sawfly distribution in Alberta in 2018-2021 (maps by David Giffen, AAFC-Saskatoon).

The survey was coordinated and conducted by Shelley Barkley from Alberta Agriculture and Irrigation and their partners and cooperators.

Pea leaf weevil

Meghan Vankosky, James Tansey, Shelley Barkley, John Gavloski, Ross Weiss, Owen Olfert, Jennifer Otani

The pea leaf weevil (Sitona lineatus) is an invasive insect to western Canada. Its primary hosts are field pea and faba bean, which can be damaged by adults feeding on foliage and by larvae feeding on the root nodules. Secondary hosts of pea leaf weevil include alfalfa, clover, and chickpea, but these plants are only affected by adult foliage feeding. The pea leaf weevil was first detected on the prairies near Lethbridge in the late 1990s, in southern Saskatchewan in 2007, and in Manitoba in 2019. Adult pea leaf weevils consume the foliage of field pea and faba bean plants, beginning in the spring, resulting in ā€˜uā€™ shaped notches along the margins of the leaves. The survey is conducted annually in the spring when field pea plants range in size between two and six pairs of leaves by counting the number of feeding notches. The number of notches is used to estimate population density, based on the expectation that increasing levels of damage are indicative of increasing population density. The monitoring protocol is available online.

Since becoming established, the range of pea leaf weevil in western Canada has expanded to the east and north. The pea leaf weevil was confirmed in the Peace River Region a few years ago, and evidence of its presence (in low to moderate densities) was observed throughout the region in 2022 (Figure 13). In the rest of Alberta, population densities were greatest in the Edmonton area and north of the Yellowhead Highway (Figure 13). Densities of pea leaf weevil were the quite low in southern Alberta, aside from some fields near the foothills (e.g., counties of Pincher Creek and Cardston), which is quite different from what has been observed in past years (Figure 14).

Pea leaf weevil populations in Saskatchewan were quite low in the western and central agricultural regions in 2022 (Figure 13), similar to observations from the survey in 2019, 2020, and 2021. However, as compared to 2021, more fields in eastern Saskatchewan had moderate to high numbers of notches per plant, with some fields having an average of 9-27 notches per plant (RMs 333, 331, 303, 301, 273 and 271, all northeast of Yorkton).

In Manitoba adult pea leaf weevils were collected and their identity confirmed in 2019. In 2022, pea fields were sampled using the protocol used in Alberta and Saskatchewan. Low to moderate densities of pea leaf weevil, based on foliar damage to peas, were observed in fields in northeast Manitoba in 2022, including fields in the Swan River Valley where pheromone traps were deployed in 2021.

Figure 13. The distribution of pea leaf weevil (Sitona lineatus) in Alberta, Saskatchewan, and Manitoba in 2022, based on a plant damage survey conducted in the spring in randomly selected field pea crops (map by Ross Weiss, AAFC-Saskatoon).

Figure 14. The distribution of pea leaf weevil observed from 2018-2021 (maps by David Giffen, AAFC-Saskatoon).

The pea leaf weevil survey was conducted by Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include AAFC, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.

Diamondback moth

Meghan Vankosky, James Tansey, Carter Peru, Shelley Barkley, John Gavloski, Ross Weiss, Owen Olfert, Jennifer Otani

Pheromone-baited traps are used to monitor the arrival of diamondback moth (Plutella xylostella) in spring across western Canada. Diamondback moths have limited ability to survive winter conditions in Canada and re-establish populations each year after migrating from the southern United States and Mexico. Adult diamondback moths were detected in 75% of the traps set up across western Canada in spring of 2022 (Figure 15).

The pheromone trap network is used to determine when adult moths arrive and this information is used for modelling the number of potential generations of diamondback moth that could be possible. Model results are communicated in the Weekly Updates each growing season. Because diamondback moth can develop from the egg to adult stage quite quickly in hot weather, the risk associated with diamondback moth to crucifer crops (including canola), increases as the number of generations increases.

Pheromone traps for diamondback moths cannot be used to determine if diamondback moth populations have reached or surpassed the economic threshold. Rather, they can serve as an early warning that diamondback moths are present and that field scouting during susceptible crop stages is required. A scouting protocol for diamondback moth larvae is available here.

Figure 15. Results of pheromone trapping for diamondback moth in spring 2022 (map by Ross Weiss, AAFC-Saskatoon).

The diamondback moth survey was conducted by Alberta Agriculture and Irrigation, the Saskatchewan Ministry of Agriculture, Manitoba Agriculture, and Agriculture & Agri-Food Canada (AAFC). This survey is funded through the AgriScience Program as part of the Canadian Agricultural Partnership, a federal, provincial, territorial initiative. Funders include AAFC, Western Grains Research Foundation, SaskWheat, Manitoba Crop Alliance, Alberta Wheat Commission, SaskPulse, Manitoba Canola Growers, Prairie Oat Growers Association, SaskCanola, and Manitoba Pulse & Soybean Growers.

2017 Swede Midge Pheromone Monitoring Results

In 2017, swede midge pheromone traps were deployed at 46 sites across the Prairie region to monitor for populations of this brassica pest. Of the 46 trap sites, two were located in BC, 19 in Alberta, 16 in Saskatchewan, and nine in Manitoba. Figure 1 illustrates trap site locations in 2017. Two pheromone traps were deployed at each site.


All of the traps were negative for swede midge in 2017. 

Figure 1.  Pheromone trap site locations for swede midge (Continarinia nasturtii) in 2017.

We are grateful to all of the producers, agronomists, and cooperators who participated in the 2017 swede midge monitoring project. Without your assistance, we could not have supported such a thorough and widespread pheromone monitoring program.


We also extend our thanks to Nancy Melnychuk (AAFC-Saskatoon) for organizing the program and distributing trapping materials, and to Jonathon Williams and Shane Hladun (AAFC-Saskatoon) for examining the returned sticky cards.


Because of the serious threat that swede midge poses to canola production, it is vital that monitoring continues across the Prairies. At this time, plans are being made for the 2018 swede midge monitoring program. Agrologists or growers interested in performing weekly monitoring in 2018 are encouraged to contact Jonathon Williams, Boyd Mori, or Meghan Vankosky for more information.


Boyd Mori and Meghan Vankosky
Agriculture and Agri-Food Canada, Saskatoon Research and Development Centre


More information about swede midge can be found by:

ā€¢ Referring to the Canola Watch article by Dr. Julie Soroka or accessing a new Ontario fact sheet produced by Baute et al. 2016.
ā€¢ Accessing the swede midge pages within the new Field Guide which is available as a free download in either English or French.