Biocontrol is defined as the use of one living organism to kill or control another organism. Fungi that parasitize insects are a valuable weapon for biocontrol. The spores of a parasitic fungus are sprayed on pest insects, attacking and controlling its host. Another fungus was identified as killing populations of silkworms as early as 1834; the spores of the same fungus are now used as a mycoinsecticide—a parasitic fungus used to kill insects—to control Colorado potato beetles. The spores of other fungi are used to control spittlebugs, leaf hoppers, citrus rust mites, and other insect pests.