Alternate uses: see Bt (disambiguation)

Bt is short for Bacillus thuringiensis, a soil bacterium that produces poisons that are toxic to a range of insects. There are several strains of Bt, which are usually quite specific as to the insect they target. Bt is also basically non-toxic to humans. It is therefore often used as a pest control agent, especially in organic farming where the use of chemical pesticides is verboten.

Recently several crops (including corn and potato) have been genetically modified to produce Bt poison proteins. This has generated some controversy, especially regarding the ill effects Bt corn was purported to have on the monarch butterfly.

See also: pesticide, organic farming, genetically modified organism