Non-target impacts of insecticides on natural enemy populations in southeastern U.S. cotton

Tarnished plant bug (Lygus lineolaris) and the bollworm (Helicoverpa zea) are two of the most economically damaging insect pests in southeastern United States cotton. Current management of these pests include both broad- and narrow-spectrum foliar insecticide sprays to protect yield. Because these materials vary in their impacts to non-target organisms (i.e., aquatic arthropods, pollinators), we asked if common cotton insecticides had differential impacts on the beneficial insect guilds present in North Carolina and Virginia. We hypothesized that broad-spectrum insecticides (pyrethroids) would have an acute effect on the beneficial insect community in comparison to more selective insecticides (insect growth regulators). To do this, a randomized complete block design was utilized to evaluate seven different insecticides with varying modes of action labeled for bollworm and plant bug control at four different locations. Plots were sprayed during peak H. zea flight to simulate a typical application window. Plots were sampled using a sweep net weekly over the following month to evaluate acute and chronic effects of insecticides over time. These results highlight the variation in non-target organisms present in cotton and the unanticipated impacts that insecticides can have on beneficial insect communities in cotton.