2017 ASHS Annual Conference

Cabbage maggot is a major insect pest in every brassica vegetable crop in Canada, and around the world. It is challenging to control because many cultural methods are often costly or impractical to implement on a large scale, and, in Canada, few insecticides are registered and available to growers. The main chemical control product is chlorpyrifos, and studies in three growing regions of the Canadian province of British Columbia in 2013 showed that 75% of cabbage maggot populations tested exhibited chlorpyrifos resistance. To date, the damage caused by cabbage maggot has been attributed to Delia radicum L. (DIPTERA: Anthomyiidae). In the summers of 2015 and 2016, a Canada-wide survey was undertaken with the goals of 1) elucidating the Delia species complex responsible for cabbage maggot damage in brassica vegetables, including broccoli, cauliflower, cabbage, daikon radish, kale and Chinese greens, and; 2) determining the prevalence of chlorpyrifos resistance. More than 40 partners were assembled across 9 of Canada’s 10 provinces, and they collected eggs, larvae, puparia and adult flies from commercial fields in their regions. Fields were georeferenced, and field history, cultural and chemical practice history and neighbouring crops were noted. Samples were sent to regional hubs for species identification and counts of relative abundance. Adult flies were allowed to emerge from puparia samples and were subsequently subjected to screening tests using the Potter spray tower to determine susceptibility to chlorpyrifos relative to a laboratory strain. Results have been assembled, analysed and Arc-GIS was used to produce practical maps of relative abundance of species in relation to crop and other regional characteristics, and of prevalence of chlorpyrifos resistance, which are made available to growers through the partners across the country to guide effective pesticide use and pesticide resistance management. The results and maps produced from this completed work are presented in this poster.