It Makes Scents

Using sex against bugs

In the war between bugs and man, the bugs have lately had the upper hand. Making a comeback from their near defeat after World War II by DDT and other chemical formulations, insects have become immune to many pesticides; their lot has also been made easier by the banning of many bug killers that are harmful to health and environment. As a result, insects are again on the march, spreading disease and inflicting costly damage on crops and forests. But now man is about to unleash a new and Machiavellian weapon against which bugs seemingly have no defense: sex.

For the first time, the Environmental Protection Agency has approved for commercial use as a pesticide an insect sex pheromone, the scent emitted by a female to attract males. The new substance, being marketed by Albany International under the trade name Gossyplure H.F., is actually a synthesized version of the scent given off by female pink bollworm moths. These insects produce caterpillars that eat their way through the cotton crops in Southern California and Arizona, costing farmers some $40 million a year in damage and control expenses.

Gossyplure proves the old adage that nothing succeeds like excess. When it is sprayed on a cotton field, it so saturates the air with female pink bollworm moth pheromone that the male moths sometimes go on indiscriminate sex orgies. They try to mate with sticks, stones, vegetation or anything else in the vicinity. However they react, they are seldom able to find the available females; they soon become so accustomed to the scent that they no longer respond to it. The result: a sharp drop in the population of caterpillar young --and crop damage. In field tests near Blythe, Calif., last year, only 10% of cotton crops treated with Gossyplure were damaged, compared with 80% in unsprayed areas.

Gossyplure won EPA approval after laboratory tests showed that it was harmless to humans, wildlife and vegetation and had no effect on other species of insects. (Standard chemical sprays used on cotton fields also kill insects that are beneficial to the crop.) It is conceivable, so to speak, that the bollworm could evolve immunity to its own sex pheromone--for example, by producing a different scent. But scientists could then synthesize the new pheromone and continue to control the frustrated moths.

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