With respect to the second charge—to determine the types of chemical products that are most appropriate for ecologically based pest management—the committee concluded that societal concerns, scientific advances, and regulatory pressures have driven and continue to drive some of the more hazardous products from the marketplace. Synthetic organic insecticides traditionally associated with broad nontarget effects, with potentially hazardous residues, and with exposure risks to applicators are expected to occupy a decreasing market share (Chapter 3). This trend has been promoted by regulatory changes that restricted use of older chemicals and by technological changes that lead to competitive alternative products (Chapter 3 and Chapter 4). Many products registered in the last decade have safer properties and smaller environmental impacts than older synthetic organic pesticides (Chapter 4). The novel chemical products that will dominate in the near future will most likely have a very different genesis from traditional synthetic organic insecticides; the number and diversity of biological sources will increase, and products that originate in chemistry laboratories will be designed with particular target sites or modes of action in mind (Chapter 4). Innovations in pesticide-delivery systems (notably, in plants) promise to reduce adverse environmental impacts even further but are not expected to eliminate them.

The committee recognized, however, that the new products share many of the problems that have been presented by traditional synthetic organic insecticides. For example, there is no evidence that any of the new chemical and biotechnology products are completely free of the classic problems of resistance acquisition, nontarget effects, and residue exposure. Genetically engineered organisms that reduce pest pressure constitute a “new generation” of pest-management tools, but genetically engineered crops that express a control chemical can exert strong selection for resistance in pests (Chapter 4). Similarly, genetically engineered crops that depend upon the concomitant use of a single chemical pesticide with a mode of action similar to that of the transgenically expressed trait could increase the development of pest resistance to the chemical. Moreover, adverse environmental impacts are still considerations (Losey et al., 1999). A recent study, for example, has revealed that a variety of transgenic Bacillus thuringiensis (Bt) corn has been found to release Bt toxins into the soils via root exudates (Saxena et al. 1999). Thus, the use of transgenic crops will probably maintain, or even increase, the need for effective resistance-management programs, novel genes that protect crops, chemicals with new modes of action and nonpesticide management techniques.

There remains a need for new chemicals that are compatible with ecologically based pest management and applicator and worker safety. Food residues have been addressed in previous National Research Council reports (for example, Pesticides in the Diets of Infants and Children,



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