Spatial and Temporal Trends in Pesticide Use and Associated Risks for California Wine Grape.

Modern agriculture relies heavily on pesticides for controlling pests, weeds, and crop diseases to assure continuing food production.  Farmers, policy makers, and other stakeholders seek tools to quantitatively assess pesticide risks, for mitigating pesticide impacts on ecosystems and human health.  This study assessed the temporal and spatial trends of pesticide use for wine grapes and the associated environmental risks.  Pesticide usage data for wine grapes in California from 2000-2008 were obtained from the Pesticide Use Reports (PUR) database.  Risk assessments were made with the Pesticide Use Risk Evaluation (PURE) indicator, which is capable of assessing site-specific pesticide risks to four environmental compartments: surface water, groundwater, soil, and air.  The risk scores for the first three environmental compartments are determined by the ratio of the predicted environmental concentrations (PEC) to the toxicity value for selected indicator organism(s); while the risk score for the air is calculated using the emission potential (EP), which is a pesticide product property for estimating potential volatile organic compound (VOC) emissions.  Maps and graphs were generated for risk of each pesticide category to each compartment throughout California.  For each pesticide category, surface water risks were higher in the coastal regions due to greater rainfall and steeper land slopes.  By comparing use trend and risk trend maps, one can identify combinations where increasing use does not necessarily translate into increasing risk, which may be due to factors such as choosing lower toxicity pesticides within a category.  In conclusion, spatial and temporal variations in risk are often associated with quantitative use changes, though differences in real-world factors which affect pesticide transport are evident in the data.