biological pest control Control of pest populations by natural predators, parasites, or disease-causing bacteria and viruses (pathogens). 

coevolution Evolution in which two or more species interact and exert selective pressures on each other that can lead each species to undergo various adaptations. See evolution, natural selection. 

DDT Dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon that has been widely used as a pesticide but is now banned in some countries. 

Economic threshold Point at which the economic loss caused by pest damage outweighs the cost of applying a pesticide.

fungi Eukaryotic, mostly multicellular organisms such as mushrooms, molds, and yeasts. As decomposers, they get the nutrients they need by secreting enzymes that speed up the breakdown of organic matter in the tissue of other living or dead organisms. Then they absorb the resulting nutrients. 

fungicide Chemical that kills fungi. 

Genetic engineering Insertion of an alien gene into an organism to give it a new and usually beneficial genetic trait. Compare artificial selection, natural selection. 

herbicide Chemical that kills a plant or inhibits its growth. 

insecticide Chemical that kills insects. 

integrated pest management (IPM) Combined use of biological, chemical, and cultivation methods in proper sequence and timing to keep the size of a pest population below the size that causes economically unacceptable loss of a crop or livestock animal.

persistence How long a pollutant stays in the air, water, soil, or body. See also inertia. 

pest Unwanted organism that directly or indirectly interferes with human activities. 

pesticide Any chemical designed to kill or inhibit the growth of an organism that people consider undesirable. See fungicide, herbicide, insecticide.