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Efficacy of the insect-parasitic nematode, Bradynema listronoti, as a biological control agent of the carrot weevil, Listronotus oregonensis

Project Code PRR19-010

Project Lead

Annie-Ève Gagnon, Agriculture and Agri-Food Canada


To improve carrot weevil control in carrot production in Ontario and Quebec by evaluating the feasibility of establishing a parasitic nematode population in commercial fields

Carrots are an economically important crop in Canada with a farm gate value of 130 million dollars in 2018. Carrot weevil (Listronotus oregonensis L.) is a major pest of carrots that causes serious economic damage in the largest acreage producing regions of Canada (Ontario, Quebec and Nova Scotia). In years of high infestation, damage from carrot weevil can result in up to a 50% reduction in carrot yield. Carrot weevil larvae chew holes in the carrot, damaging the marketable products and leaving the carrot susceptible to secondary infection by bacteria and fungi. Bacteria and fungi can also then lead to additional post-harvest damage during storage. It was previously thought the carrot weevil was present for a single generation during the growing season in many growing regions in Canada. However, there have been confirmed reports of the development of a second generation in Ontario and Quebec, increasing the need to develop management strategies for this pest.

Currently the most common way to control carrot weevil in Canada is through the use of insecticides. Alternatives to pesticides are however required by organic growers, and as a resistance management tool for conventional growers. A previous study conducted by Agriculture and Agri-Food Canada discovered a parasitic nematode, Bradynema listronoti in isolated fields in Quebec. In vitro experiments showed a 60-fold reduction in infected female fecundity, making it highly likely that this nematode could contribute to reducing carrot weevil levels in the field. This project will test and improve nematode rearing methodologies, generate data on what densities of the nematode are required for different levels of carrot weevil control and determine the potential for establishment in new commercial fields without an historic presence of the nematode. The data generated will inform future projects to develop B. listronoti as a native, Canadian biological control agent contributing to sustainable, long term integrated pest management approach for carrot weevil.

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