In this video, Scott Meers, insect management specialist with Alberta Agriculture and Forestry talks about cabbage seedpod weevil populations in Alberta and Saskatchewan, what could be confused with feeding symptoms and how many weevils constitutes a threshold for chemical control.
It should come as no surprise to insect geeks that the ash-grey insect above with a rather distracting snout is a weevil. More specifically, it’s a cabbage seedpod weevil (Ceutorhynchus obstrictus), an insect pest that has been infecting canola crops (and other Brassicaceae species) in Alberta since the mid-1990s, and it has since moved across the southern portion of the province and into Saskatchewan.
Adult cabbage seedpod
weevils will often drop to
the ground and play dead
Adult cabbage seedpod weevils overwinter in leaf litter, emerging in the spring to feed on floral buds, seeds, nectar and racemes. Females lay eggs into developing pods, and resulting larvae can consume upwards of 5-6 seeds, ultimately leaving the seedpod as mature larvae to pupate within the soil. And besides directly biting into yield through the consumption of seeds, larvae may also indirectly affect yields by causing damage to seedpods, which leaves them more susceptible to shattering.
According to Alberta Agriculture and Forestry, thresholds are reached when an average of 3 to 4 adults are collected per 180° degree sweep sample at 10 to 20% flowering.
Canola School videos are produced by Real Agriculture.
You can find all of the episodes on Real Agriculture's Canola School page