Managing resistance is critical to future use of pyrethroids and neonicotinoids

I are often referred to as having a broad or narrow spectrum of activity, depending on the diversity of pest species they kill. Narrow-spectrum insecticides are generally thought of as being less disruptive to biological control and more environmentally benign because of their specificity to a few target pest species. In the presence of a complex pest community, however, use of an insecticide with a high degree of specificity can require additional applications of products that target other taxa. The ability of organophosphate (OP), organochlorine and methyl carbamate insecticides to control a broad range of insects with a single application led to their widespread use for pest control. With the cancellation of DDT by the U.S. Environmental Protection Agency in 1973, followed by bans on the use of most other organochlorines, agricultural use of the OP and methyl carbamate insecticides became dominant, with more than 200 OP insecticides available worldwide at their peak. OPs and methyl carbamates are still widely registered for use on California crops and have been regarded as especially important tools for growers of vegetable and fruit crops, which are unique and economically important components of California’s agricultural industry. California Department of Pesticide Regulation (DPR 2003) reports of OP usage for 2002 (the most recent data published) indicate that chlorpyrifos, diazinon and malathion are the most widely used OPs, while methomyl and carbaryl are the only two methyl carbamates used to any great extent (table 1). The widespread use of these products has led to the development of pesticide resistance in many insect populations (Roush and Tabashnik 1990). Their use has also raised concerns about surfacewater contamination, resulting in the listing of some California rivers as impaired waterways under the U.S. Clean Water Act. The U.S. Food Quality Protection Act (FQPA) of 1996 has focused particular attention on the human risks of exposure to OPs and has already imposed restrictions on their use (see page 7). In a recent report funded by the California Department of Food and Agriculture (Metcalfe et al. 2002), pyrethroid and neonicotinoid insecticides were identified as the most likely alternatives to the OPs. Even before the OPs are withdrawn, however, the number of applications of