Luring good bugs to feed on the bad.

Luring good bugs to feed on the bad

In recent years, chemists have characterized an increasing number of insect pheromones -- chemical attractants that bugs use to find each other. Already many are used commercially to lure pests to a trap or to confuse pests by attracting them to a bait rather than a mate. In fact, note Jeffrey R. Aldrich and his colleagues at the Agriculture Department's Insect and Nematode Hormone Laboratory in Beltsville, Md., of the more than 200 insect pheromones that have been identified, all but two have been for pests.

Until now. Aldrich's team has begun focusing on identifying and synthesizing the lures for an entirely different class of bugs -- those that feed on pests. Baits containing these predator pheromones can be used to draw in beneficial insects to feed on resident pests. Perhaps at least as important, they may also serve to protect the community of beneficials that arrive by offering a means of luring them out of fields or gardens before insecticides are sprayed.

Predators can be drawn to a new home by congregating pheromones, chemical attractants normally emitted when members of their species have scouted a rich feast of prey. As a result, Aldrich says, the agricultural use of congregating pheromones in baits should not encourage the buildup of insect resistance to a chemical the way toxic-chemical pesticides now do. In fact, he says, it "should actually select for the evolution of greater responsiveness by [beneficial] predators to man-made pheromones."

To date his group has identified the active ingredients in pheromones of several "true bugs" (Hemiptera) that prey on agriculturally important larval pests. While each bug responds only to its own species-specific pheromone, additional mixed-in chemicals have not reduced a predator pheromone's potency. (This is a sharp contrast, Aldrich says, to what has been observed for most pest pheromones.) The finding suggests that pheromones for several beneficial insects might be successfully combined in a single bait, he says. Aldrich expects that such baits, initially targeted for home gardeners (an enthusiastic market for alternative pest-control products), could become commercially available within "a few years."