Integrated pest management of root maggots in Ontario leafy green and root brassica vegetables

Brassica leafy green vegetables (cabbage, broccoli) and root vegetables (rutabaga, turnip) are important and economically profitable crops in Ontario. Damage to these crops from insects impacts their marketability and yield, with cabbage root maggot (Delia radicum) being the most concerning pest. Chlorpyrifos applied to transplants at time of seeding or as a mid-season soil drench is the most commonly used option for root maggot control. However, all uses of chlorpyrifos in brassica vegetables will be phased out by 2024. In light of the loss of this key control tool, the Pest Management Centre’s (PMC) Priority Setting Workshop for IPM selected sustainable management of Delia root maggots to meet this need of Brassica vegetable growers. Field trials were initiated in 2022 in Exeter, ON to evaluate various combinations of IPM tactics to manage Delia root maggots in cabbage and rutabaga crops. The strategies include physical barriers (netting), biological controls (nematodes) and the combination of both, based on grower experience and feasibility for potential uptake. The strategies will be compared to conventional management practices (seed and transplant treatment with cyantraniliprole). The project is expected to develop and facilitate the adoption of IPM systems for Delia root maggots that combine practical and effective alternative tactics that are easy to implement, are cost effective, and provide multiple mechanisms for reducing Delia spp. populations, with reduced reliance on insecticides.