Early warning pesticide monitoring in Nevada’s surface waters

A pesticide is a substance, or mixture of substances, used to kill or control insects, weeds, plant diseases, and other pest organisms (Nevada Department of Agriculture, 2019). Commercial pesticide applicators, farmers, and homeowners apply about 1.1 billion pounds of pesticides annually to agricultural land, non-crop land, and urban areas throughout the United States (Atwood and Paisley-Jones, 2017). Although intended for beneficial uses, there are also risks associated with pesticide applications, including contamination of groundwater and surface-water resources, which can adversely affect aquatic life and water supplies. Pesticides can contaminate groundwater and surface water directly through point sources (spills, disposal sites, or pesticide drift during an application). The main avenue of contamination, however, is indirect by non-point sources, which include agricultural and urban runoff, erosion, leaching from application sites, and precipitation that has become contaminated by upwind applications (fig. 1, Thodal and others, 2009).