2012 Cabbage Seedpod Weevil Forecast

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Cabbage seedpod weevil was first found infesting canola in southern Alberta in 1995, since then, the weevil has spread to south-central Alberta and southwestern Saskatchewan. The distribution and abundance of the cabbage seedpod weevil have been monitored yearly in western Canada since 1997. Predictive models based on climate data indicate that this pest will eventually disperse to all regions of canola production in western Canada, including the Peace River region.

The 2011 survey covered all the canola growing areas of Alberta with over 320 fields sampled in 44 municipalities. The cabbage seedpod weevil is still only found in the southern areas. There was no significant expansion of the cabbage seedpod weevil range in Alberta in the past year. The northern limits of the range include (from west to east) Rocky View County, Kneehill County, Special Areas 2, Special Areas 3, and the MD of Acadia. Producers in Wheatland County had to consider control for the first time in 2010. The cabbage seedpod weevil is still not found in central Alberta or in the Peace River region.

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While this is not a true forecast, the numbers of weevils found at most sites south of Highway 1 have the potential to result in economically damaging populations in the next growing season. Cooler temperatures and rainfall in August favors the development of the new generation of weevils and may lead to higher numbers in 2012. Any producers that grow canola in southern Alberta and into the south portion of central Alberta will have to check their canola crops as they come into flower. The earliest flowering canola crops tend to have the highest risk from cabbage seedpod weevil and should be monitored very closely.

Cabbage seedpod weevil overwinters as an adult so the risk of infestation is further indicated by the adult population of the preceding fall. High numbers of weevil adults in fall will likely mean significant infestation levels in the following spring. This map does not adjust for the emergence of the new generation in the fall or overwintering conditions.

The cabbage seedpod weevil takes roughly eight weeks to develop from egg to adult. Development time will vary somewhat depending on weather conditions, especially temperature. There is one generation per year. Follow this link for further information about the life cycle.

Crop damage from cabbage seedpod weevil can occur from:

bud-blasting (potentially reducing yield in dry years)
larval feeding within developing pods (larva consumes about five seeds)
premature shattering of damaged pods
new generation adults that emerge in the fall feeding on nearly developed seeds.

The larval feeding alone can result in yield losses of 15 to 20 percent in each pod infested.

Cabbage seedpod weevil adult abundance is best monitored by using sweep net samples. Sampling should begin when the crop first enters the bud stage and continue through the flowering period. Select ten locations within each field, and at each location count the number of weevils from ten 180 degree sweeps. Sampling locations should include both the perimeter and interior of the field to obtain a representative estimate of weevil numbers throughout the field.

This monitoring procedure will also give an indication of the number of lygus bugs present and may serve as an early warning for lygus damage, provided that the same fields are monitored into the early pod stage.

The 2011 cabbage seedpod weevil survey was carried out by Alberta Agriculture and Rural Development with support from the Applied Research Associations (Southern Applied Research Association, Chinook Applied Research Association, Lakeland Applied Research Association, Battle River Research Group, Gateway Research Organization , and Smoky Applied Research and Demonstration Association) and the toll free number 310-2777 (Alberta Pest Surveillance System). Thank you for your contribution.

Frequently Asked Questions

Canola Council of Canada

For pesticide options visit Alberta Agriculture's Pesticide Selector.

Alberta Insect Pest Monitoring Network 2011 Annual Report

For more information on this insect and its management contact the Ag-Info Centre at 310-FARM (3276) or bugs.r.us@gov.ab.ca.

2012 Cabbage Seedpod Weevil Forecast

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