Safety of Bacillus thuringiensis var. kurstaki Applications for Insect Control to Humans and Large Mammals

This minireview discusses the risks to humans and large mammals associated with the use of Bacillus thuringiensis var. kurstaki (Btk) in forest, agricultural and urban environments. The first subspecies used for insect control was Bacillus thuringiensis subsp. thuringiensis (Btt), known at the time as Bt Berliner. Much of the early work done with Bt does not identify the subspecies. Btk is registered for use against many species that are pests in agriculture, forestry and horticulture. Btk is currently the most widely used insecticide in forestry in Canada. Review of the literature indicates that Btk is safe for the environment and its various components. Since its introduction in the 1960s, no scientifically documented case of human infection has been reported as a result of its use in forestry or agriculture against various defoliators or in urban environments during gypsy moth eradication programs. No human health problems have been proven to be attributable to the application of any Bt product on crops used for human consumption. Based on all available information, Btk is considered by most people to be the safest bioinsecticide available at present.