Note that this is not a forecast. It is a survey of the situation in Alberta in 2019.
The 2019 survey covered all the canola growing areas of Alberta (except the Peace region) with 266 fields sampled in 51 municipalities and 40 reports from our online reporting tool.
2019 Cabbage seedpod weevil survey map (PDF, 2.4 MB)
The cabbage seedpod weevil was once again found at economic levels in southern Alberta; however, many fields were below threshold levels and on average the numbers were lower than normal. This is the third consecutive year that cabbage seedpod weevil numbers have been lower than normal but this insect still requires close monitoring for all producers in southern Alberta, especially in its traditional range south of Highway 1. In 2019, Alberta saw a return to the northern range extensions of 2016, with individual weevils found in Wetaskiwin, Strathcona and Lamont.
Despite lower numbers in 2019, it will still be important to scout canola in early flower to make control decisions in southern Alberta. We have seen economic threshold levels as far north as a line between Red Deer and Consort Alberta in the past and those areas should monitor very early flowering canola.
Jennifer Otani, Agriculture and Agri-Food Canada conducts the canola survey in the Peace River region where no cabbage seedpod weevils have been found yet.
History of infestation
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.
For more information, see Historical Cabbage Seedpod Weevil population maps.
While this is not a true forecast, the numbers of weevils found through this survey in southern Alberta and the southern counties of central Alberta counties indicate a potential of 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 the 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 favours the development of the new generation of weevils and may lead to higher numbers in the following year. Very cold winters do have the potential to reduce overwinter survival of cabbage seedpod weevil adults.
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. Find out more information about the cabbage seedpod weevil.
The 2019 cabbage seedpod weevil survey was carried out by Alberta Agriculture and Forestry with support from Chinook Applied Research Association, Gateway Research Organization, Lakeland Applied Research Association, Battle River Research Group, Farming Smarter and Agriculture and Agri-Food Canada, Lacombe and from the web-based reporting tool Thank you all for your contribution.
Thank you also to David Giffen, Agriculture and Agri-Food Canada, Saskatoon for preparing the map.