An invasive weevil that entered Canada in the 1930s has now spread to the eastern edge of Manitoba, and northwestern Manitoba now claims some of the highest recorded feeding levels on the Prairies. Agriculture Canada entomologist Meghan Vankosky says growers in newly affected areas need to monitor fields early — and rethink their management assumptions.
Read Also
World’s winter wheat crops look good for now
Winter wheat crops look good in the Black Sea and the U.S., although there is plenty of drought in the U.S. winter wheat region.
Pea leaf weevil continues to expand its range across the Prairie provinces, with some of the highest recent feeding levels now recorded in western Manitoba.
Speaking at CropConnect in Winnipeg, Meghan Vankosky, research scientist and entomologist with Agriculture and Agri-Food Canada in Saskatoon, said the invasive pest has steadily pushed east over the past three decades and is now well established across much of the region.
WHY IT MATTERS: Experts have been closely watching the spread of pea leaf weevil in Manitoba. The pest is now recorded across all Prairie provinces and has reached the Ontario border — putting growers in areas of new establishment at risk of economic losses in field peas and faba beans.
First detected in Canada in the 1930s in British Columbia, pea leaf weevil moved into southern Alberta in the mid-1990s and Saskatchewan in the mid-2000s before being confirmed in Manitoba in 2019.
“It has moved quite far north and also quite far east,” Vankosky said.
Prairie Pest Monitoring Network surveys show that in 2025 some of the highest feeding levels were recorded in western Manitoba, in areas where populations were likely high enough to cause economic damage in field peas and faba beans.
The most recent monitoring map suggests the pest’s Prairie-wide establishment is now complete, with detections reaching the Ontario border.
Life cycle and what to watch for
Pea leaf weevil produces one generation per year, with adults active in spring and again in late summer. In spring, adults move into pea and faba bean fields and feed along leaf margins, leaving distinctive crescent-shaped notches. While the foliar feeding is visible, the more serious damage happens below ground.
Larvae feed on root nodules, reducing the plant’s ability to fix nitrogen and affecting both yield and seed quality.
Weather plays a role in population dynamics. Wet conditions tend to favour survival in the soil stage, while drought can limit larval development.
Monitoring focuses on counting feeding notches on seedlings between the second and sixth node stages. Nominal thresholds are 30 per cent of field pea seedlings showing damage to terminal leaves and 15 per cent in faba beans.
Management options remain limited
Management options remain limited for pea leaf weevil. Although foliar insecticides are registered, recent work in southern Saskatchewan found no yield benefit from applying a foliar spray.
Seed treatments can offer protection, but they must be applied at planting, before growers know what adult pressure will be in a given field. Evidence suggests seed treatments can protect yield, but the benefit depends on weevil density.
“There is no strong evidence that foliar insecticides protect against yield loss,” Vankosky said.
That puts growers in a difficult spot, particularly in areas where the pest is still expanding and pressure can vary widely from year to year.
“If you are planning to plant peas or beans in an area that had very high populations last year, you might want to consider applying the seed treatment,” she added.
Researchers are also studying alternatives to insecticides. Beneficial insects such as ground beetles have shown some ability to feed on pea leaf weevil eggs and adults, and work is underway to better understand how much natural impact enemies may have on populations.
Trap cropping — planting early strips of peas or faba beans to attract and concentrate adults — is also being explored, though it requires further field-scale testing.
With the insect now established across all Prairie provinces, Vankosky encouraged growers to monitor fields closely in early spring and consult the local survey maps produced annually by the Prairie Pest Monitoring Network.
Key takeaways for prairie growers
- Pea leaf weevil is now established across all Prairie provinces and has been detected as far east as near the Ontario border.
- In 2025, some of the highest recorded feeding levels were in western Manitoba — including areas with likely economic damage.
- Foliar insecticides do not protect yield. Seed treatments at planting are the main management option.
- Economic thresholds are 30 per cent of pea seedlings with terminal leaf damage, and 15 per cent for faba beans.
- Monitor Prairie Pest Monitoring Network survey maps each spring for local population updates.
