Spatial and Temporal Trends In Pesticide Use and Associated Risks for California Almond.

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 almond and the associated environmental risks. Pesticide usage data for almond in California from 1992-2010 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 (i.e., fungicide, herbicide, and insecticide) to each compartment throughout California. 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.