Colorado Potato Beetle Resistance to Carbofuran and Several Other Insecticides in Quebec1

Abstract

Laboratory tests showed that a strain of Colorado potato beetle (CPB) Leptinotarsa decemlineata (Say), from Sherbrooke, Quebec, was resistant to most of the insecticides currently recommended for use as compared with a susceptible strain from London, Ontario. The level of resistance shown by the Sherbrooke strain to carbofuran was very high (> × 1,600). This strain was resistant also to DDT, endrin, endosulfan, azinphosmethyl, phosmet, methidathion, methamidophos, phorate, chloethocarb, and carbaryl. Aldicarb and some pyrethroid insecticides were toxic to both CPB strains. However, the Sherbrooke strain was slightly more tolerant (× 1.3) to aldicarb than the London strain and also showed low-level (≤ × 2.0) cross resistance from DDT to the pyrethroid insecticides. These results suggest that resistance to aldicarb and the pyrethroid insecticides may also soon occur.