Cabbage Seedpod Weevils – New to Central Alberta 

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Canola growers in Central Alberta should be aware of increasing populations of cabbage seedpod weevils (CSPW). Surveys in 2025 and observations heading into 2026 indicate higher numbers of overwintering weevils across a larger area than growers have historically experienced, with populations now being found north of Red Deer. 

Scout Early 

Begin scouting flixweed patches, volunteer canola, and other canola-related weeds for early signs of weevil activity. CSPW are highly attracted to the colour yellow and often congregate in the earliest flowering areas of a field. 

While these field edges and early-flowering patches are good places to locate weevils, treatment decisions should be based on field-wide sampling. 

When to Sweep 

Sweep for CSPW from the early bud stage through 10–20% flowering, particularly in early-seeded fields that attract the first migrating adults. The economic threshold is 25–40 weevils per 10 sweeps, averaged across the field. A practical sampling approach is to collect sweep-net samples in four locations throughout the field and average the results. 

Understanding the Damage 

Female cabbage seedpod weevils lay eggs in developing canola pods. Once hatched, each larva can consume approximately 5–8 seeds before completing development. 

However, timing is critical when considering insecticide application. Spraying too early can reduce effectiveness because: 

  • Pods are not yet large enough to support egg laying. 
  • No economic damage occurs until pods reach approximately ½ to ¾ inch (1–2 cm) in length. 
  • Additionally, weevils may still be migrating into the field, especially in very early flowering crops. 

Applying insecticide before the majority of weevils have arrived may result in reduced control and the need for additional intervention. 

Learn More 

Additional information on cabbage seedpod weevil can be found through the Canola Encyclopedia and Alberta Agriculture. For local advice and assistance with scouting or threshold decisions, contact Alberta Canola Agronomist Keith Gabert at 587-377-0557.