Comparative aspects of cry toxin usage in insect control

Abstract

Crystalline (Cry) endotoxins from Bacillus thuringiensis (Bt) and related toxins are currently being used as active ingredients of bacterial insecticides and as expressed proteins in genetically modified plants. While both approaches take advantage of the specificity of Cry toxins against various insect orders, there are characteristic differences between these technologies in (i) form of application; (ii) compatibility with agrotechnologies; (iii) composition of the active ingredients; and (iv) their environmental fate. The technical advantage of Bt plants is that they eliminate labor-and energy-demanding field applications of insecticides against insect pests manageable with Cry toxins. In turn, however, Bt plants continuously produce Cry toxin during vegetation. As a result, these Bt plants do not comply with the principle of integrated pest management, as Cry toxin administration cannot be limited to the duration of the occurrence of the insect pest targeted. Bt insecticides and Bt plants may also differ in their active ingredients (bacterial protoxins and plant-expressed preactivated toxin), which in addition to pesticide registration issues, has pronounced effects on Cry toxin resistance and environmental persistence in stubble.