Assessing potential non-target risks of biological control agents used in integrated pest management against cabbage seedpod weevil, Ceutorhynchus obstrictus.

Project code: PRR03-370

Project Lead

Peter Mason - Agriculture and Agri-Food Canada

Objective

To evaluate the potential non-target risk of a biological control strategy for management of cabbage seedpod weevil, an insect pest of canola

Summary of Results

The cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham) [CSW] is an herbivorous weevil, native to Europe and adventive in North America. This invasive species is a serious pest of canola and rapeseed (Brassica napus L. and Brassica rapa L.) in North America. Biological control using parasitoids (natural enemies) from the area of origin is a promising, cost effective and environmentally friendly strategy to reduce pest populations. Research conducted during this study contributed significantly to better understanding the problem posed by CSW and the challenges for developing control strategies to combat this pest. Surveys conducted in eastern and western regions of Canada confirmed that CSW continues to spread and eventually it will occur throughout the canola growing areas of Canada.

Although biological control of CSW was attempted more than 60 years ago, it had been deemed to be unsuccessful. Data generated through this project and a spin off taxonomic project showed that two of the three agents released failed to establish and in subsequent studies mis-identifications of parasitoids reared from CSW led to the erroneous conclusion that biological control had failed. Field studies in Canada and Europe provided reared specimens for a taxonomic review that clarified the identity of the parasitoids associated with CSW and indicated that the parasitoid communities in the area of introduction were very different than that in the area of origin. The latter communities varied between regions (east and west) and consist of native parasitoid species that are likely opportunists (i.e. generalists) and have little impact on the invasive CSW. Results from Europe confirmed that Trichomalus perfectus(Walker) and Mesopolobus morys (Walker) are the dominant parasitoids and are good candidates for introduction as biological control agents because they appear to be specific to the target species. Regulations governing the introduction of natural enemies for biological control have become more stringent and host range testing is now an important requirement for assessing the safety of candidate species. In Canada, new host plant - weevil - parasitoid associations were documented and research continues to fill the knowledge gaps. Non-target host test lists were developed and a submission was drafted for comment by the Canadian Food Inspection Agency. Outputs from this project included five scientific publications, one poster and a Non-target Host Test List for submission to the CFIA. This project advanced the initiative of implementing biological control of CSW and was the basis for a new project funded for 4 years through the AAFC peer review initiative.

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