Calgary, Alta. (Rural Roots Canada) – The cabbage seedpod weevil is spreading across Alberta, according to Alberta Canola.
Surveys conducted in 2025, along with observations heading into the 2026 growing season, indicate higher numbers of overwintering weevils across a wider area than growers have historically experienced.
Canola growers in Central Alberta in particular are being advised to scout early, as populations have now been identified as far as areas beyond Red Deer.
Alberta Canola is encouraging growers to begin scouting early-flowering areas, including flixweed patches, volunteer canola and other canola-related weeds where cabbage seedpod weevils are often first found.
The insects are highly attracted to the colour yellow and tend to gather in the earliest-flowering areas of fields. However, growers are reminded that treatment decisions should be based on field-wide sampling rather than observations at field edges.
Scouting with a sweep net should begin from the early bud stage through 10 to 20 per cent flowering, particularly in early-seeded fields that attract migrating adult weevils.
Read more: Canada thistle tops Alberta’s 2025 invasive species list
The economic threshold for treatment is 25 to 40 weevils per 10 sweeps, averaged across the field. A recommended approach is to collect sweep-net samples from four locations throughout the field and calculate the average.
Female cabbage seedpod weevils lay eggs inside developing canola pods. Once hatched, larvae can consume approximately five to eight seeds before completing development.
Agronomists say timing is critical when considering insecticide applications. Applying too early may reduce effectiveness because pods may not yet be large enough to support egg laying, and economic damage does not occur until pods reach approximately half to three-quarters of an inch in length.
Early applications can also miss weevils that continue migrating into fields, potentially reducing control and increasing the risk of additional intervention.
More information on cabbage seedpod weevil management is available through the Canola Encyclopedia and Alberta Agriculture.
