http://mmbr.asm.org/cgi/content/full/62/3/775

The leading biorational pesticide, Bacillus thuringiensis, is a ubiquitous gram-positive, spore-forming bacterium that forms a parasporal crystal during the stationary phase of its growth cycle. B. thuringiensis was initially characterized as an insect pathogen, and its insecticidal activity was attributed largely or completely (depending on the insect) to the parasporal crystals. This observation led to the development of bioinsecticides based on B. thuringiensis for the control of certain insect species among the orders Lepidoptera, Diptera, and Coleoptera (for a review, see reference 33). There are more recent reports of B. thuringiensis isolates active against other insect orders (Hymenoptera, Homoptera, Orthoptera, and Mallophaga) and against nematodes, mites, and protozoa (109, 110). B. thuringiensis is already a useful alternative or supplement to synthetic chemical pesticide application in commercial agriculture, forest management, and mosquito control. It is also a key source of genes for transgenic expression to provide pest resistance in plants.