A pest is any living thing—a plant, an animal, or a microorganism—that has a negative effect on humans. Labeling an organism, a pest is a very subjective concept that varies with each individual’s point of view. In general, pests are unwanted or undesirable because they: 1.) reduce the availability, quality, or value of human resources such as food, feed, water, or space; 2.) injure humans, animals, crops, structures, and possessions; 3.) spread or cause disease; or 4.) interfere with human activities by causing annoyance, discomfort, or inconvenience. Learn more about pests below.