Geographic variation in the Colorado potato beetle resistance to imidacloprid

Colorado potato beetle, Leptinotarsa decemlineata (Say), the most important insect defoliator of potatoes, is notorious for its ability to develop insecticide resistance. Resistance levels and the rate of imidacloprid excretion and metabolism were quantified in resistant and susceptible populations from different geographic locations including Maine, Michigan and Long Island, NY. Values of susceptibility were equivalent in the susceptible populations, and the highest resistance ratios were found in the Long Island, NY population followed by the Maine and Michigan populations. Resistant beetles treated with 14C-imidacloprid metabolized more compound than susceptible beetles. The cytochrome P450s inhibitor piperonyl butoxide (PBO) suppressed imidacloprid metabolism, with the effect being stronger in the susceptible populations. It appears that resistance has a similar mechanism (P450s) in all resistant populations despite resistance levels and geographic variation.