Efficacy of conventional and organic pesticides following ingestion by cabbage maggot (Delia radicum)

Cabbage maggot (Delia radicum) is a devastating pest to Brassicaceae crops around the world and specifically within the Willamette Valley in Oregon, USA. Chemical control methods for this pest are limited, with reduction or elimination of chlorpyrifos tolerances and expensive alternative chemistries; therefore, there is an increasing need to determine novel chemical control options. The efficacy of four organic and four conventional insecticides was evaluated in laboratory bioassays in Aurora, Oregon, USA. The mortality of adult female cabbage maggot flies was assessed after ingestion of insecticides. Organic insecticides spinosad and azadirachtin were highly effective with 90% mortality within the first twenty-four hours after exposure while erythritol and a new insecticide, V-10433, were moderately effective with 80% mortality twenty-four hours after exposure. Conventional insecticides generally resulted in faster mortality than organic. Flies fed zeta-cypermethrin had a mortality of 84% within two hours of exposure while 90% of flies fed cyantraniliprole and bifenthrin died within sixteen hours of exposure. The identified insecticides with high or moderate efficacy have the potential to be incorporated into baits or lures that could be used to control cabbage maggot in a field setting.