Click Bait? Efficacy of Group 30 insecticide cover crop treatments on Virginia wireworm species

Wireworms are the generalist, subterranean larvae of click beetles (Coleoptera: Elateridae). Species worldwide are persistent pests of numerous crops, including potatoes and sweetpotatoes by feeding on seeds and tunneling into tubers. This damage leads to both diminished yields and quality, causing significant economic losses for farmers. Although historically soil-applied insecticides have been successful in combating wireworms, the deregistration of previously used insecticides (cyclodienes, organophosphates, and carbamates) has left few remaining options. Broflanilide belongs to a new insecticide mode of action group, the GABA-gated Cl-channel allosteric modulators (Group 30), and has shown promise in Canada against Agriotes spp. wireworms. To assess its potential against Melanotus spp. wireworms, which predominate across regions of the U.S., we conducted container bioassays and multiple field trials in Virginia utilizing broflanilide and clothianidin seed treatments. The results of the greenhouse bioassay showed significant mortality in proximate wireworms to both broflanilide (86.7%) and clothianidin (93.3%) wheat seed treatments. Field trials of the same treatments showed more variable results but did find a significant difference in our broflanilide treatment. Some sites showed no significance, likely due to low wireworm presence. Based on our findings, the use of Group 30 insecticide treatments may not be as effective in the field as supported by results achieved in Canada. This suggests that there may be underlying regional differences related to the efficacy of these insecticides, possibly related to species-level biological differences. Further investigation is necessary to determine the factors correlated to the success of Group 30 treatments as Virginia field applications.