Contamination of pollinator conservation habitats in Illinois with neonicotinoids

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Shih-Huai Cheng, Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, IL, Alex Harmon-Threatt, University of Illinois and Anthony Yannarell, Natural Resources and Environmental Sciences, University of Illinois at Urbana-Champaign, Urbana, IL

Background/Question/Methods
Neonicotinoids comprise a broad group of systematic insecticides that are widely used as agricultural seed coat treatments for corn and soybean. Due to their long half-lives, neonicotinoids may persist in agricultural soils that have been taken out of production. With increasing pollinator conservation habitats established on retired croplands, concerns have arisen about the effects of soil contamination on ground-nesting bees as studies have shown that neonicotinoids can affect pollinator longevity and behavior. Furthermore, many pollinator conservation habitats are embedded within agricultural landscapes, and they may be subject to insecticide drift. An insecticide drift could occur during sowing and plowing when the activities generate neonicotinoid-contaminated dust from abraded seed coat particles and surface soil. To estimate the effects of insecticide drift and the turnover rate of neonicotinoid residues along with soil depth, we conducted realistic field studies at several Illinois pollinator conservation habitats in 2019 and 2020. We collected airborne dust deposition using sticky dust traps and soil cores at four different depths (0-05 cm, 05-10 cm, 10-20 cm, 20-30 cm). In the study, we examined the concentration of three neonicotinoids (clothianidin, thiamethoxam, and imidacloprid) using Chromatography-Tandem Mass Spectrometry (LC-MS/MS).
Results/Conclusions
The average total neonicotinoid concentration found in the soil samples was 0.180 ± 1.49 ng/g (mean ± standard error) and 0.241 ± 4.18 ng/g (mean ± standard error) for 2019 and 2020, respectively. For both years, we observed a correlation between total neonicotinoid concentration and soil depth (P < 0.001 in both 2019 and 2020). We observed higher average accumulation rates of neonicotinoids in the 0-05 cm soil cores when compared to soils at depth. Our analysis of 2019 dust trap samples indicate that the most extreme concentration of total neonicotinoid were detected during the weeks in which corn and soybean planting progress increased the most rapidly. These results demonstrate that off-farm habitats experience periodic input of neonicotinoid resides that is potentially related to farming activity, and they highlight the need to further investigate the effects of neonicotinoid residue drift.