Potential of biocontrol of cabbage seedpod weevil in the Canadian Prairies

Cabbage seedpod weevil is a European invasive pest of canola in North America. Two wasps, Trichomalus perfectus and Mesopolobus morys, are the main parasitoids of this weevil in Europe. Although none have been released in Canada, T. perfectus is established in Quebec and appears to keep weevils under threshold. Thus, it has been suggested as a candidate for redistribution to western Canada. In this presentation we review the potential impact of prairie farming practices, landscape and climate on establishment of parasitoids. Factors that positively impact parasitoid establishment include early seeding of canola, adoption of integrated pest management strategies including proper timing of insecticide spraying where unavoidable, and conservation of semi herbaceous habitats surrounding the fields as they provide favorable overwintering sites for adult parasitoids. Hot and dry periods are potential limiting factor, although, bioclimatic models suggest that establishment of T. perfectus is possible in all Canadian canola growing areas of the Prairies. Part of our ongoing studies include assessment of the current parasitism rate of weevils in southern Alberta and determine species composition. Results from our studies will be added to a wider national effort to complete an environmental assessment of classical biocontrol of this weevil using T. perfectus in the Prairies.