Friday, April 30, 2010

Attack of the MIT Gypsy Moths

“Oh, I’m so sorry,” the MIT student guide apologized as moths fluttered around my wife and soon-to-be-college age daughter. Trying to appear unconcerned, my wife assured her it was no big deal, even though the moths were not interested in the rest of the group – just the two of them. “This has never happened before,” the guide added sympathetically. It wasn’t their fault, I’m to blame and I was 4,000 miles away at the time! Here is the story.

Every spring ODA staff put up thousands of gypsy moth traps around the State. Maybe you’ve seen the cardboard, tent-shaped traps, each about the size of a shoe, hanging from trees. Inside each trap there is a sticky substance for catching the moths and a little plastic lure strip. The lure is a pheromone. It gives off the same chemical that female gypsy moths emit when they are ready to mate.

This pheromone is odorless to humans, but it is attractive to male gypsy moths at incredibly low concentrations. Each lure strip is no bigger than a 1-inch piece of spaghetti, yet all summer long it emits minute amounts of pheromone and any male gypsy moths in the area follow the scent plume to the trap. Just a few traps per square mile are all it takes to cover the State.

I have personal experience with the incredible attractiveness of these chemicals. My office is at ODA headquarters in the same area where the gypsy moth trapping staff is based. I rarely handle a trap, but traps with suspect moths are brought into the office now and then so there are times when gypsy moth pheromone is in the air. Some of it sticks to my clothes.

Now and then my family travels to Maine to visit relatives. If we arrive in the summer, my clothes and luggage are attractive to gypsy moths, even though they are laundered regularly. If I stand in one place, they find me. Gypsy moths have been a pest in the Northeast for over a century.

The clothes of other family members that are washed with mine also pick up some of the pheromone, thus the embarrassing incident at MIT. Other people have had similar experiences. One woman worked at a factory where gypsy moth pheromone was produced. She told me she couldn’t wear skirts outdoors in the summer in the Northeast because male gypsy moths would approach just above ground level, then flutter around in gradually rising circles. That is normal male moth behavior when they approach a tree with a waiting female. Thankfully, embarrassment is the only hazard.

Most moths and many other insects use pheromones. They are as normal a part of nature as the scent of pine trees and the perfume of roses.

Insect pheromones have been used successfully and safely as lures in detection trapping programs for nearly 40 years. Some suppression programs use pheromones in a technique called mating disruption.

Last year there was a proposal to try mating disruption on a population of a new invasive pest in California. Government officials proposed using the pheromone of light brown apple moth to disrupt its mating. It was a very innovative proposal and much better for the environment than the other treatment options. Unfortunately, that proposal was derailed by a public outcry likening the proposed treatment to aerial spraying of poisonous pesticides like DDT. In fact, the only similarity was the application method. Pheromones are not pesticides any more than Channel #5 is a poison.

Though government officials in California haven’t thrown in the towel yet, it looks more and more likely that light brown apple moth will spread to Oregon and the rest of the continent. The result will be another pest for farmers and gardeners, and more use of pesticides. That is not a good thing.

Keeping invasive species out in the first place is obviously the best strategy, but early detection and rapid response (often using a pesticide) is important too. Rapid response with an environmentally benign tool, like a pheromone or biological pesticide, is preferable when we have those tools. We should support their development and use them whenever possible for dealing with harmful invasive species.

Dan Hilburn

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