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Neonicotinoid insecticide removal by prairie strips in row-cropped watersheds with historical seed coating use

This study assessed the value of prairie strips at removing residual neonicotinoid contaminants two years after seed treatment had stopped being used. Researchers looked for neonicotinoids in the groundwater, surface water runoff, and soil samples in sites with prairie strips and sites without prairie strips (the control). The mean groundwater neonicotinoid concentrations from prairie strip sites were significantly lower than mean concentrations collected at control sites. Soil concentrations in sites with prairie strips were lower than control site soil concentrations. It is worth noting that researchers found variability in subsurface soil detections. More specifically, soil detections at two of the three prairie strip sites had higher concentrations in 2016 than 2015. In general, surface water concentrations were lower for sites with prairie strips than the controls. Findings indicate that prairie strips reduce the amount of neonicotinoid offsite movement.

Researchers also tested plants in the prairie strips for neonicotinoid contamination. They did not detect neonicotinoids in the prairie plants tested suggesting that 2 to 3 years after cessation of using neonicotinoid seed coatings, prairie plants are unlikely to result in exposure to pollinators or herbivorous insects from uptake of the neonicotinoids. Overall, the findings from this study show that several years after discontinuing seed treatment residual neonicotinoid contamination from the planting of neonicotinoid coated seeds can be reduced by prairie strips. Two to three years after the cessation of planting neonicotinoid coated seeds, these same prairie strips can also provide safe habitat for pollinators and other insects.

Xerces’ staff caution that these findings should not be extrapolated to assume that prairie strips near fields where neonicotinoid coated seeds are still being planted are safe for pollinators and herbivorous insects.

Authors: 
Hladik, M.L., S. Bradbury, L.A. Schulte, M. Helmers, C. Witte, D.A. Kolpin, J.D. Garett, M. Harris
Journal: 
Agriculture, Ecosystems and Environment
Year published: 
2017