An Integrated Vegetated Treatment System for Mitigating Imidacloprid and Permethrin in Agricultural Irrigation Runoff.

Pyrethroid and neonicotinoid pesticides control an array of insect pests in leafy greens, but there are concerns about the off-site movement and potential water quality impacts of these chemicals. Effective on-farm management practices can eliminate aquatic toxicity and pesticides in runoff. This project evaluated an integrated vegetated treatment system (VTS), including the use of polyacrylamide (PAM), for minimizing the toxicity of imidacloprid and permethrin pesticides in runoff. The VTS incorporated a sediment trap to remove coarse particles, a grass-lined ditch with compost swales to remove suspended sediment and insecticides, and granulated activated carbon (GAC) or biochar to remove residual insecticides. Runoff was sampled throughout the VTS and analyzed for pesticide concentrations, and aquatic toxicity using the midge Chironomus dilutus and the amphipod Hyalella azteca. In simulated runoff experiments, the VTS reduced suspended sediment load by 88%, and imidacloprid and permethrin load by 97% and 99%, respectively. In runoff events from a conventionally grown lettuce field, suspended sediment load was reduced by 98%, and insecticide load by 99%. Toxicity was significantly reduced in approximately half of the simulated runoff events, and most of the lettuce runoff events. Integrated vegetated treatment systems that include components for treating soluble and hydrophobic pesticides are vital tools for reducing pesticide load and occurrence of pesticide-related toxicity.