Pesticide Exposure in Wet Meadows of Southeast Idaho, 2025

Wet meadow habitats in southeast Idaho, which are important areas for wetland-dependent wildlife, are managed by four National Wildlife Refuges (NWR). Threats to this important, but regionally declining habitat include pesticide drift from adjacent and nearby lands. In this study, four NWRs, Camas, Minidoka, Bear Lake, and Grays Lake, are investigated for the presence of pesticides. Pesticide applications occur in agricultural croplands adjacent to Camas and Minidoka NWRs while Bear Lake and Grays Lake NWRs are approximately 15 miles to the nearest croplands. Objectives of this study include determining variance of pesticide exposure among NWRs based on adjacent land uses and distance from refuge boundary and assessing the seasonal pesticide exposure in wet meadows of chemicals used in agricultural croplands and invasive species control efforts. To answer these questions, silicone bands, cleaned and provided by the U.S. Geological Survey (USGS), were placed as a passive collection method from May through September 2025 in wet meadow habitats where butterfly (lepidoptera) and bumblebee (bombus) use surveys were conducted. Three to four sampling sites, 700 to 1,000 meters apart, were established in wet meadows along transects originating near the boundary of the refuges. Given the configuration of wet meadow habitats at the NWRs, sampling sites were established in additional wet meadows to assess variation of pesticide exposure within each refuge. Silicone bands were collected and stored by U.S. Fish and Wildlife Service (USFWS) staff according to USGS protocols and shipped to USGS California Water Science Center at the end of the 2025 field season for analysis by the USGS Organic Chemistry Research Laboratory in Sacramento, CA.