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Use of Insect Netting for Cabbage Maggot Control

The cabbage maggot is one of the most chronic and challenging agricultural insect pests facing vegetable growers in Canada -- maggot feeding can kill or stunt young plants and reduce the marketability of mature root crops. Cabbage maggot populations are showing increased resistance to chlorpyrifos, the only insecticide registered in Canada for cabbage maggot. Seventy-five per cent of cabbage maggot populations tested in British Columbia in 2013 were resistant to chlorpyrifos. Agriculture and Agri-Food Canada (AAFC) scientists are working to bring a technology now used on thousands of acres of brassicas across the European Union to Canadian growers. They are examining the use of insect netting to control cabbage maggot on vegetable brassicas such as cabbage, broccoli, cauliflower and rutabaga.

The AAFC team first evaluated a long-lasting polyethylene insect netting (1.3 millimetre-gauge) against the cabbage maggot on rutabaga in the four Atlantic provinces. The netting successfully protected the crop against cabbage maggot, but weed pressure under the netting sometimes reduced marketable yields because rutabaga requires season-long protection. Although spraying can be performed through the netting, efficacy was sometimes decreased. In the current project, the team is studying use of the netting in brassica vegetables like cauliflower, broccoli and kale, which need only early-season protection against cabbage maggot; the netting is removed after a few weeks, and weeds are controlled as usual. Three different gauges of netting are being tested in Atlantic Canada and British Columbia for their ability to exclude other brassica pests (for example, flea beetles) as well as cabbage maggot. Abiotic conditions under and outside the netting are being measured. The project also includes a survey of resistance to chlorpyrifos in cabbage maggot populations across Canada.

Once the best practices for using the netting have been developed, the team will focus on increasing grower adoption/uptake of the technology through use of social media, field demonstrations, platforms such as regional commodity/extension networks and public data sites, videos showing specialized machinery installing and removing the netting, and through classical approaches like factsheets.

This project was funded by the Pest Management Centre, Pesticide Risk Reduction Program.

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