Wierenga_1994_Pest.Sci_40_259

Several metabolic enzymes were assayed in susceptible and insecticide-resistant (R-mfo and R-AchE) strains of the Colorado potato beetle (Leptinotarsa decemlineata Say). We compared the activities of esterases, glutathione transferases and mixed function oxidases, and measured in-vivo metabolism of carbofuran to determine the contributions of metabolic factors to the observed resistance. There were no substantial differences between strains in alpha- or beta-naphthylacetate hydrolysis, or in glutathione transferase activity. Compared to the susceptible strain, the R-mfo strain showed 4-fold higher activity in both ethoxyresorufin-O-dealkylase, and pentoxyresorufin-O-dealkylase activity. The R-AChE strain had a 1.5-fold higher level of ethoxyresorufin-O-dealkylase activity. Correspondingly, the in-vivo metabolism of carbofuran was highest in the R-mfo strain, and the R-AChE strain was slightly higher than the susceptible strain. These results are discussed in relation to other resistance mechanisms which we have examined in these strains.