IDENTIFICATION OF NEONICOTINOID INSECTICIDES IN IOWA GROUNDWATER

Neonicotinoid insecticides have rapidly gained popularity for both urban and agricultural use. Since their introduction in 1994, they have become the most widely used class of insecticides in the world. Neonicotinoids have been viewed as ideal replacements for other insecticides (e.g., organophosphates, carbamates) due in part to their perceived limited environmental impacts and lower mammalian toxicity. Within the agricultural sector, they are preferred over other insecticides as: 1) having a high selectivity and potency for insects, 2) having a lower toxicity to vertebrates, and 3) being active systemically. The agricultural use of neonicotinoids has dramatically increased over the last decade, primarily due to the increased use of treated seeds. For example, the annual neonicotinoid use in Iowa increased from 61.9 kg in 2001 to 374,863 kg in 2014.

While neonicotinoids have been documented as almost ubiquitous in Iowa streams with the highest concentrations observed during the planting season following rain events, less is known regarding the presence of neonicotinoids in Iowa groundwater. To help fill this data gap, a network of 40 wells in alluvial aquifers across portions of Iowa and Minnesota were sampled in 2017. Conditions in these wells typify aquifers most vulnerable to surface contamination, with well depths ranging from 3.5 to 61 m with median well depth of 7.6 m. All samples were analyzed for seven neonicotinoid active ingredients. This presentation will describe the results of this study and provide recommendations for future research.