Exploring potential mechanisms of pyrethroid-resistance in annual bluegrass weevil (Listronotus maculicollis)

The annual bluegrass weevil (Listronotus maculicollis) is the most destructive pest of short-mown turfgrass in eastern North America. Since the 1990s, pyrethroids have been commonly applied in spring during adults' migration from overwintering sites to playing surfaces. However, overuse of this class of insecticides has led to an observed decrease in sensitivity to pyrethroids as well as unrelated insecticide classes. Pyrethroid resistance is believed to be partially mediated by enhanced enzymatic detoxification, but studies that quantify enzymatic activity have not been conducted. To that end, three L. maculicollis populations with varying levels of pyrethroid sensitivity were exposed to different rates of bifenthrin for four hours before extracting proteins and measuring the enzymatic activity of the three most common detoxifying enzymes (P450s, carboxylesterases, and glutathione S-Transferases). The pyrethroid resistance of each population was assessed via a dose-response petri-dish assay. There was no significant difference in carboxylesterase activity between populations or between treatments. P450 activity was significantly different between populations as well as within one population. The most resistant population (as identified in bioassays) displayed the greatest P450 activity while the most sensitive population displayed the least. These findings are an important step in characterizing the mechanisms by which L. maculicollis are able to tolerate the various control practices utilized against them.