Optimization of an Integrated Vegetated Treatment System Incorporating Landguard A900 Enzyme: Reduction of Water Toxicity Caused by Organophosphate and Pyrethroid Pesticides

Acknowledgements This report is the product of a collaborative project among regional, state, and federal agencies involved in reducing pesticide runoff in California. The Resource Conservation District (RCD) of Monterey County was the lead agency procuring and administering the United States Department of Agriculture (USDA) Conservation Innovation Grant which funded the majority of this work. The author's thank Paul Robins and Rami Shihadeh for administering the grant and organizing grower outreach meetings where results of this project were presented to central coast growers and local resource agencies. The California Department of Pesticide Regulation (DPR) provided matching funds used for field work and pesticide analyses of water samples. The authors thank Robert Budd and Kean Goh for their support and guidance, and Sue Peoples for coordinating the chemical analyses. conducted the toxicity tests and chemical analyses for this project, and their diligence and professionalism is much appreciated. This work could not have been completed without the cooperation of Salinas Valley growers concerned with improving surface water quality on the central coast; the author's appreciate their continuing participation in this research. The agricultural fields of Monterey County contain a $4 billion/year industry that produces much of the nation's lettuce, strawberries, crucifer crops and grapes. Runoff from irrigated agriculture contributes a significant amount of water to local stream flow, and several studies have measured significant pesticide concentrations and biological impacts in the Salinas River and its watersheds (Anderson et al., 2003b; Hunt et al., 2003; Phillips et al., 2004). Pesticides in runoff from irrigated vegetable production can also impact invertebrate communities (Anderson et al., 2003a; Liess and von der Ohe, 2005; Anderson et al., 2006b), have adverse impacts on salmonids (Scholz et al., 2000), and lead to food web magnification in fish and wildlife (Pereira et al., 1996). Results of studies conducted throughout California have demonstrated that surface water toxicity is caused by organophosphate and pyrethroid pesticides (Anderson et al., 2011). Developing effective systems for the treatment of runoff is necessary to reduce pesticide loading to aquatic habitats and is an integral requirement of recent Central Coast Water Quality Control Board regulations. The integrated vegetated treatment system (VTS) in the current study was constructed on a working farm in a narrow linear ditch. This system was previously evaluated by Anderson et al. (2011), and consisted of a short sediment settling basin followed by a vegetated portion, and treatment with Landguard™ OP-A enzyme, which …