Transgenic host plant resistance to insects - Some reservations

Transgenic host plant resistance to insect pests is currently based on gene s coding for single toxic chemicals transferred from nonrelated organisms a nd producing levels of the toxins sufficient to give the plants virtual imm unity. Such levels of toxins have the potential to reduce yields, to select quickly for strains tolerant to the toxin, to harm natural enemies, and to increase the resistance of pests to other toxins, including traditional in secticides. Moreover, when the same toxin is also available as a spray appl ication (e.g., the B, thuringiensis toxin), tolerance to the transgene will mean that the efficacy of the alternative delivery system is also lost. Al l this is in sharp contrast to the usually beneficial interactions between more broadly based traditional plant resistance and both biological control and insecticides. The analogy can be made between the enthusiasm currently focused by multinational agrochemical and seed companies as well as by far mers on transgenic plant resistance to pests and the enthusiasm that greete d DDT in the 1940s. However, the problems referred to above are a contrast with traditional plant breeding, which is not usually the existing technolo gy that transgenic plant resistance is seeking to replace. More usually the existing technology to be replaced is routine application of insecticides- the contrast here is very much in favor of transgenes.