Distribution of Cyclodiene-Insecticide Resistance in the Seed Maggot Complex in Relation to Cropping Practices in Southwestern Ontario1

Abstract

A survey conducted at 29 locations in southwestern Ontario indicated that seed maggots ( Hylemya platura (Meigen): H. liturala (Meigen) complex) have become generally resistant to cyclodiene insecticides. The percentage of resistant individuals varied considerably in relation to type of farming and the resulting insecticide program. In corn and pasture areas 76% of the population remained susceptible, 62% in crucifer-growing areas, 27% in vegetable-growing areas, and 22% in tobacco-growing areas. Both H. plalura and H. lilurata were resistant in the tobacco-growing area of Norfolk and Elgin Counties. The results are discussed in relation to residues of cyclodiene insecticides in soil, soil type, and the possibility of extended movement of adults. The practical implications of the work also are discussed.