What is this Bt toxin that is in the food we eat? Bacillus thuringiensis is an insecticide with unusual properties witch make it very useful for pest control in certain situations. Bacillus thuringiensis is a naturally occurring bacterial disease in some insects. It is very common in the soils around the world. There are many strains of Bt that can infect insects and kill them. The Bt toxin has been developed because of this unusual property. The insecticidal properties of Bt were first discovered in 1911. The commercial use, although, was not available until the mid-fiftys. In recent years, there has been renewed interest in Bt and several new products have been developed, because of the human safety associated with Bt-based insecticides. Also, strains of this bacterium have been produced to affect certain fly larvae, such as mosquitos and leaf beetles.Although the Bt toxin is used worldwide it does have its down side. Bt-based products tend to have a shorter shelf life than other insecticides. Manufacturers indicate that it has reduced effectiveness after two to three years of storage. Shelf life is greatest when it is stored in cool, dry areas that are out of direct sunlight. Bt is also very susceptible to degradation by sunlight Most formulations only stay active for less than a week following the application. With some of the newly developed strains, there has been even shorter persistence lasting less than twenty-four hours. The manufacturers have been experimenting with several ways to increase the longevity of the Bt toxin after the application. One of these involves inserting Bt toxin crystal genes into other species of bacterium that can better survive on the surfaces of crops. The specific activity of Bt limits their use on crops where several pests are present. Bt functions as a stomach poison insecticide. Thus it has to be eaten and the application must cover as much of the plant to be effective. This also poses more limi...
