| Abstract: | Pyrethroid insecticides effect excellent control of a wide range of insect pest species at low cost to the user. In outlets where a broad spectrum of pests occur, alternative compounds are often more expensive and frequently have to be combined to provide an acceptable spectrum of control. The benefits of the pyrethroids have led to their extensive and often exclusive use in many of these outlets around the world. However, such dependency on a single class of chemistry brings with it the attendant threat of resistance. Pyrethroid resistance has now been documented in many species of insect around the world and for several of these, changing to other insecticides has meant large increases in the cost of control programs. Analysis of the US insecticide market has shown that in 1987 the average insecticide cost to a mid-south cotton grower was $32 acre?1 (1 acre = 0-405 ha). A hypothetical case was examined where resistance to the pyrethroids occurred in one key pest, Heliothis virescens, the tobacco budworm. The level of resistance was defined such that 50 % of the normally pyrethroid-treated area was now treated with the most cost-effective alternative. Under these conditions, a mid-south grower would see the cost of insect control nearly double to $61-50 acre. Extrapolating such increases to the whole US cotton crop or to global cotton production would lead to increased insecticide costs of $230 × 106 and $1-4 × 109 per year, respectively. Making similar assumptions for all crops, the increased global costs of only a moderate amount of pyrethroid resistance could be as high as $2-4 × W9 annually. There is, thus, a very real need to maintain the pyrethroids as effective insect-control agents for as long as possible. |
