Photo credit: Kevin Dooley

The Great Lakes are the world’s largest freshwater ecosystem. A new study published in the journal Environmental Pollution aimed to quantify the extent to which neonicotinoid insecticides were transported to the Great Lakes via rivers and streams. U.S. Geological Survey scientists collected water samples from 10 major tributaries to the Great Lakes every month for an entire year. Neonicotinoid insecticides were detected in every tributary every month. Imidacloprid was the most commonly detected neonicotinoid (53%), followed by clothianidin (44%) and thiamethoxam (22%). Acetamiprid and dinotefuran were detected in 2% or fewer of the samples, while thiacloprid was not detected at all. Concentrations of detected neonicotinoids increased in the spring and summer – the time during which neonicotinoid-coated seeds are planted and pesticide sprayings are most common.