A pesticide is any chemical or mixture of substances intended to destroy, prevent, repel, or mitigate pests (U.S. EPA, 2012). Pests include animals, insects, unwanted plants (weeds), fungi, microorganisms such as bacteria and viruses, and prions. The term pesticide includes to a number of different subgroups of substances, most commonly insecticides, herbicides, and fungicides. While the definition of a pesticide is broad, it excludes drugs used to control human or animal diseases; plant fertilizers, nutrients, or other plant growth regulators; biological control agents (i.e., beneficial predators such as ladybugs or birds that feed on insects), and certain products containing low-risk substances that are exempt from federal pesticide regulations (e.g., cedar chips, mint oils, and garlic. Many common household products are pesticides, including cockroach sprays and baits; insect repellents; kitchen, laundry, and bath disinfectants and sanitizers; and a variety of lawn and garden products (U.S. EPA, 2012).
Pesticides play an important role in controlling insects, weeds, pests, and disease-causing organisms in society (U.S. EPA, 2012). Effective pesticide use allows farmers to maintain stable crop yields and thereby provide food and food products at a lower cost to consumers. In addition, pesticides have significantly helped control the spread of vector-borne diseases throughout history, including malaria, the West Nile virus, and yellow fever (see this document for more info on other vector-borne diseases). However, because pesticides are designed to kill living organisms, these substances can also harm humans, other animals, and the environment more generally. Thus, pesticide use inherently creates risks for other, non-targeted species (U.S. EPA, 2012).