Development of Insecticidal Resistance by Soil Insects in Canada1

Abstract

Tests on soil insects collected from a number of areas in Canada indicated that the dipterous insects are rapidly becoming resistant to the cyclodiene insecticides. Four species of root maggots were found to be resistant; the onion maggot, Hylemya antiqua (Meigen); the seed-corn maggot, H. cilicrura (Rondami) and the closely related species, H. liturata (Meigen); and the cabbage maggot, H. brassicae (Bouche). The spotted root fly, Euxesta notata (Wiedemann), exhibited a high degree of tolerance to aldrin and dieldrin. Diazinon® (D,O-diethyl O -(2-isopropyl-4-methyl-6-pyrimidinyl) phosphorothioate), Trithion® ( O,O -diethyl S-p -chlorophenylthiomethyl phosphorodithioate), ethion, and V-C-13 ( O -, 2,4-dichlorophenyl O,O -diethyl phosphorothioate) were all highly toxic to adult flies of the Anthomyiidae. The Common cutworm species of economic importance in southwestern Ontario, Agrotis ipsilon (Hufnagel) and Peridroma saucia (Hubner), showed no indication of cyclodiene resistance. The organophosphate insecticides were generally less toxic to cutworms than the cyclodiene insecticides. The dark-sided cutworm, Euxoa messoria (Harris), was highly tolerant to dieldrin, DDT, and Diazinon. Cyclodiene resistance has developed in areas where broadcast applications of insecticides have been applied to the soil over several consecutive years. It was suggested that, in order to slow the development of oregano phosphate resistance, procedures other than broadcast applications should be utilized with the oregano phosphate insecticides when feasible.