GW 09: Ground Water Monitoring for Imidacloprid and Four Degradates in High Use Areas in California
Abstract
Imidacloprid, an active ingredient on the Ground Water Protection List (GWPL), was selected for well monitoring based on its use patterns and physical-chemical properties. Well selection was based on soil type, pounds of imidacloprid applied, depth to water, and well location. From February to March 2009, the Department of Pesticide Regulation (DPR) sampled thirty-four wells in Monterey, San Benito, San Luis Obispo, Santa Barbara, and Ventura counties for imidacloprid and other herbicides on the “triazine screen” (hexazinone, tebuthiuron, simazine, bromacil, prometon, atrazine, norflurazon, and diuron). Monitoring for these other herbicides allows DPR to assess the performance of our ground water protection program. No residues of imidacloprid, imidacloprid degradates, or herbicides on the “triazine screen” were detected in any of the wells tested. These results are similar to a 2004 imidacloprid monitoring study that also yielded no detections of the parent or its degradates. If the use of imidacloprid increases or is applied in a way that facilitates leaching to ground water, the DPR may conduct further monitoring of imidacloprid in the future.