|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 2014 survey covered all the canola growing areas of Alberta with 290 fields sampled in 49 municipalities. The cabbage seedpod weevil is still only found at economic levels in southern Alberta.
The Municipal District of Pincher Creek was added to the survey in 2014 and economic levels of cabbage seedpod weevil were found there.
Generally weevil numbers were lower than in previous years in southern Alberta and there was less spraying than in a typical year. Unfortunately this does not necessarily mean cabbage seedpod weevil numbers will stay low in future years. It will be important to scout fields as they come into flower in 2015.
The range of economic levels did not expand in 2014 but the northen range of the weevil did appear to push further north to the southern boundaries of Red Deer, Stettler, Paintearth and Provost counties. This expansion has happened in the past as well but did not persist so it will be important to watch the population over the next couple years.
While this is not a true forecast, the numbers of weevils found at most sites in counties where Highway 1 transects the county and south of Highway 1 have the potential to result in economically damaging populations in the next growing season. 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, although cooler temperatures and rainfall in August favors the development of the new generation of weevils and may lead to higher numbers in the following year.
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 five to eight seeds, this is the major source of losses)
- 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 2014 cabbage seedpod weevil survey was carried out by Alberta Agriculture and Rural Development with support from the Applied Research Associations (Farming Smarter, Chinook Applied Research Association, Lakeland Applied Research Association, and Battle River Research Group) and the toll free number 310-2777 (Aberta Pest Surveillance System). Thank you for your contribution.
Special mention to Jennifer Otani, Agriculture and Agri-Food Canada, for the canola survey in the Peace region where no cabbage seedpod weevils have been found to this point. Thank you David Giffen, Agriculture and Agri-Food Canada, Saskatoon for building the map.
Frequently Asked Questions
Canola Council of Canada
For more information on this insect and its management contact the Ag-Info Centre at 310-FARM (3276) or firstname.lastname@example.org