Pesticides in Minnesota Lakes

Pesticide water quality samples were collected from randomly selected lakes in Minnesota in 2007, 2012 and 2017 in conjunction with the United States Environmental Agency's (USEPA) National Lake Assessment (NLA). With the exception of two detections of the insecticide chlorpyrifos in 2017, all other pesticide detections were very low compared to the applicable water quality reference values. In each of the NLA years, the majority of detections were herbicide degradates and herbicides. The number of pesticide compounds detected and associated concentration of those compounds tended to increase with an increasing amount of row crop production in a lakeshed. In contrast, increasing amounts of forest in a lakeshed lead to fewer pesticide detections and lower pesticide concentrations.