I Thought We Had Such Chemistry
Humanity's crusade to control insects would be funny if it weren't such a serious business. We are hapless Goliaths perennially outmaneuvered by these disease-carrying, crop-destroying, soul-crushing Davids of the animal kingdom. Even when we do manage to execute an impressive assault, the offending mosquitoes or lice or potato beetles eventually return fire by developing resistance to the poison we've attacked them with. While they wait for us to develop even stronger poisons, surely they must chuckle to themselves as all the evidence of negative environmental and health consequences piles up.
The field of synthetic semiochemicals represents a kind of rearguard action in the war. Organisms naturally emit semiochemicals to influence the behavior of other organisms. There are many subsets to this class of substances, but for the purposes of pest control, chemical ecologists deal mostly with pheromones, which carry important messages between individuals within a species.
Producing pheromones in a lab makes it possible to alter or interrupt those messages. When synthetic sex pheromones of the tomato pinworm are attached to tomato vines, for example, the male is bewildered to the point of impotence: he doesn't know with whom to mate and he dies a bachelor -- whereupon the pinworm population quickly subsides, and the tomato harvest flourishes.
Unlike conventional insecticides, semiochemicals aren't poisons. Their target populations show no sign of developing resistance, and they harm nothing but their intended victims. "As a tool in integrated pest management, they're vital," says Allard Cossé, an entomologist at the U.S. Department of Agriculture. Semiochemicals, he adds, can help reestablish equilibrium in monoculture environments, where insect pests aren't confronted with the predators that would keep them in check in natural environments.
Since they are copies of naturally occurring phenomena, synthetic pheromones can't be patented. Instead, commercial developers funnel R&D into the design of distribution systems, which can. One of these companies, California-based ISCA Technologies, has developed a system it calls Specialized Pheromone and Lure Application Technology, or SPLAT. Pheromones are volatile: if they are not applied to the right surface under the right conditions, their unique properties will quickly deteriorate. SPLAT sidesteps such pitfalls by using a formulation viscous enough to adhere to bark or other plant surfaces, but thin enough to be dispersed via caulking guns, backpack sprayers, even tractors and airplanes. (Most pheromonal lures must be affixed by hand.)
"In many cases," says Agenor Mafra-Neto, a chemical ecologist and CEO of ISCA, "it's possible to achieve season-long control with one application." His formulation is biologically inert, biodegradable, and capable of withstanding heavy rain and sunlight.
ISCA has been conducting SPLAT field trials in Idaho and Wyoming that deploy a hybrid formulation of attractant pheromones and a conventional insecticide. The target is the mountain pine beetle, an arthropod that has devastated pristine pine forests in vast swaths of western North America. Initial trial results are promising: four dollops per tree will deter infestation, Mafra-Neto says.
Meanwhile, even if we're far from enjoying the last laugh in our epic struggle with rapacious insects, let's at least indulge a chuckle over the thought of a pine beetle attempting to mate with a dollop of SPLAT.