Bacillus Thuringiensis

An evaluation of the risks to human health and the environment posed by the use of Bacillus thuringiensis (Bt) as a microbial agent for pest control. It opens with an overview of the biological properties of Bt and commercial Bt products. Particular attention is given to the mechanisms by which sporulation produces inclusion bodies, containing insecticidal crystalline proteins, which are selectively toxic for insect species in the orders Coleoptera, Diptera and Lepidoptera. The second chapter reviews data elucidating the mechanisms by which Bt exerts its toxic action on susceptible insect larvae, and the next chapter, which focuses on the survival and activity of Bt in the environment, compares habitats where Bt subspecies occur naturally with treated habitats. A chapter on commercial production describes methods of production and general patterns of use in agriculture and forestry, and in large-scale programmes to control the vectors of malaria and onchocerciasis. The most extensive chapter evaluates the large number of studies conducted to assess the toxicity of various preparations containing insecticidal crystalline proteins, spores, and vegetative cells.
On the basis of this review, the report concludes that Bt products are unlikely to pose any hazard to humans or other vertebrates or to the great majority of non-target invertebrates, provided the commercial product is free from non-Bt micro-organisms and biologically active products other than the insecticidal crystalline proteins. It further concludes that Bt products can be used safely for the control of insect pests of agricultural and horticultural crops and forests.