Insecticide options for cabbage seedpod weevil
Insecticide options for cabbage seedpod weevil (CSPW)
It is important not spray too soon, as the weevil will typically continue to invade for at least a week to 10 days beyond the opening of the first flowers. Damage does not occur until pods are large enough for egg laying.
Insecticide applications target adults when crops are at 10-20% flowering stage (when 70% of plants have at least 3-10 open flowers) to avoid eggs being laid in newly formed pods. Spraying at this stage will allow the weevils more time to move into the field, but at the same time it is still early enough to keep them from laying a significant number of eggs in newly forming pods. Spraying after this stage when populations are at or above threshold may result in yield loss and will also impact beneficial insects, including pollinators, which have moved into the field.
If an insecticide application is required, spray in the morning or evening when temperatures are between 15-24° C to protect pollinators and achieve best results. Avoid spraying under a strong temperature inversion or when temps exceed 25° C.
If the economic threshold is reached for CSPW and conditions also warrant a fungicide for sclerotinia stem rot management, holding out CSPW control until 20% bloom provides an opportunity to tank mix insecticide with the fungicide application. This is a little later than the ideal timing for CSPW but the earliest stage for fungicide labels.
See the Saskatchewan Guide to Crop Protection for insecticides registered for control of cabbage seedpod weevil in canola.
Best management practice: Control of alternative host plants, including brassicaceous weeds and volunteer canola in all crops prior to the bud stage of the canola crops, is important to manage CSPWs.