Neonicotinoid Levels Exceed EPA Benchmarks in Half of Waterways on Illinois Protected Lands

Neonicotinoids have become widely used pesticides due to their specificity for insects. We explored how these contaminants are distributed on protected lands within Illinois. We hypothesized that there would be lower insect biomass at sites with higher neonicotinoid concentrations which we expected to occur at sites with a higher surrounding proportion of agriculture. We predicted that neonicotinoid levels would be highest at the start of the season, coincident with planting, then taper off throughout the growing season. Our results revealed that 25 of 50 sites surveyed had concentrations of at least one neonicotinoid (imidacloprid or clothianidin) over United States Environmental Protection Agency (EPA) benchmarks for chronic exposure. Imidacloprid had high detection above EPA benchmarks in Cook County while clothianidin was more often above benchmarks in central Illinois. There was a negative relationship between clothianidin levels and ratio of agriculture on measured insect biomass at sites with a higher proportion of agriculture. We did not identify a clear peak of imidacloprid or clothianidin concentrations. This study suggests the high level of contamination found at protected sites is concerning for ecosystem health as insects are the target prey for many wildlife species.