Biopesticides: Pesticides composed of very large numbers of a biological control agent, generally a pathogen. For example, Bacillus thuringiensis (often called B.t. for short) is a bacterium that kills insects and can be produced on an industrial scale. When sprayed, much like a chemical, this pathogen kills insects and does not persist long in the environment. Its advantage over many chemicals is that it is not toxic to birds, mammals and fish. The fact that it is not a specialist natural enemy allows commercial companies to sell it for use against various pest insects and thus obtain a large market for the product. The disadvantage is that it may kill non-target insects in the same family as the pest, or even of many other insect families which are more distantly related (see also economics of biological control).