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

Bryn M Phillips,Thomas R Lockhart,Michael Cahn,Jennifer P Voorhees,Katie Siegler,Laura Mccalla,Ron S Tjeerdema,Xin Deng,David L Chambers

doi:10.3390/toxics9010007

Bryn M Phillips, Thomas R Lockhart + Show 7 more

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https://doi.org/10.3390/toxics9010007

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Abstract

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.

Highlights

Growers rely on applications of pyrethroid and neonicotinoid pesticides for the control of an array of insect pests in leafy greens
Integrated vegetated treatment systems have been shown to reduce pesticide-associated toxicity to invertebrates in runoff [2,7]. While these systems are effective at reducing organophosphate and pyrethroid pesticides, they have not been evaluated for treating more soluble insecticides, such as the neonicotinoid imidacloprid
Imidacloprid concentrations were reduced by 45–76% in the vegetated treatment system (VTS) prior to the carbon filtration, which further reduced the concentrations by a total of 88–94% (Table 1)

Summary

Introduction

Growers rely on applications of pyrethroid and neonicotinoid pesticides for the control of an array of insect pests in leafy greens. Effective on-farm management practices are needed to reduce pesticide load and eliminate aquatic toxicity of pyrethroid and neonicotinoid pesticides in runoff. Neonicotinoid pesticides are very water soluble and pyrethroid pesticides are very hydrophobic and are transported on suspended sediments in runoff. Management practices that can mitigate both water-soluble and insoluble pesticides are needed to minimize off-site impacts to water quality Both retention basins and vegetative treatment systems (VTSs) reduce suspended sediments and hydrophobic pesticides in runoff [1]. Integrated vegetated treatment systems have been shown to reduce pesticide-associated toxicity to invertebrates in runoff [2,7] While these systems are effective at reducing organophosphate and pyrethroid pesticides, they have not been evaluated for treating more soluble insecticides, such as the neonicotinoid imidacloprid. Imidacloprid is used in conjunction with pyrethroids on most lettuce crops in the Salinas Valley, and has recently been detected in waterways receiving runoff in the central coast region of California [10]

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