Estimating Screening-Level Risks of Insecticide Exposure to Lepidopteran Species of Conservation Concern in Agroecosystems

The U.S. Fish and Wildlife Service defines ‘at risk’ species as those that have either been petitioned for listing, proposed for listing, or assigned a candidate species status under the Endangered Species Act. There are over 30 ‘at risk’ lepidopteran species in the U.S., several of which are found in the north central states. For these species, loss of habitat and exposure to pesticides, particularly insecticides, is often considered a threat to population recovery. Given their range, re-establishment of habitat in agricultural landscapes is typically identified as a primary conservation practice to support species recovery. To evaluate risks associated with habitat established in close proximity to crop fields, estimates of insecticide exposure and toxicity are needed for these species. Based on an evaluation and integration of environmental monitoring and toxicity studies reported in the peer-reviewed literature, we explore an approach to develop screening-level risk analyses for lepidopteran species of conservation concern using data obtained for pyrethroid, organophosphate, neonicotinoid, and diamide insecticides. More specifically, we interpret the utility of existing insecticide residue data to estimate host plant-mediated exposure for lepidopteran species. Based on available lepidopteran topical and dietary toxicity data, we generate Species Sensitivity Distribution models for topical exposures to pyrethroid and organophosphate insecticides. We compare the toxicity results with modeled or available exposure data to explore the potential insecticide risks associated with establishing non-target lepidopteran habitat in agricultural landscapes. Finally, we identify data gaps and needs for future monitoring and toxicity studies