Methodology
The 2024 survey covered the canola growing areas of southern and central Alberta. 222 fields in 50 municipalities were sampled in late June to early July when canola was at 20 to 25% flower. Surveyors sample by taking 25, 180 degree sweeps through the crop starting at the field edge and walking toward the centre of the field.
The survey found cabbage seedpod weevil at or below economic levels in southern Alberta with the exception of a couple of hotspots. There could have over threshold, but the nature of a random survey means they might not be sampled. In southern Alberta, it will still be important to scout canola when in early flower, especially those first to flower fields, to make control decisions.
In 2024 we found weevils in Wetaskiwin County, one weevil in 3 out of the 5 fields sampled. These counts were well below threshold but it has been a while since we have seen weevils north of Ponoka County.
Agriculture and Agri-Food Canada at Beaverlodge conducts the canola survey in the Peace River region where as of yet no cabbage seedpod weevils have been found.
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 favours the development of the new generation of weevils and may lead to higher numbers in the following year.
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