Each year, forests in the northeastern United States are plagued with leaf-eating gypsy moths. There have been many efforts to control moth populations with pesticides. But as entomologist Robert Walz tells LOE host Steve Curwood, Indiana has its own way of battling the pests: pheromones.
CURWOOD: And you’re listening to NPR’s Living on Earth. The gypsy moth has plagued the forests of the northeastern United States by eating the leaves of deciduous trees such as oak and aspen. The descendents of a single pair of gypsy moths can denude millions of square feet of leaves in just two short generations. Authorities usually try to cope with gypsy moths by spraying pesticides. But Indiana is trying insect perfume. Dr. Robert Walz is an entomologist for the Indiana Department of Natural Resources. He’s here to explain how they’re using tiny flakes of synthetic moth pheromones. Welcome to Living on Earth.
WALZ: Its good to be here. Thank you.
CURWOOD: Can you tell me about the pheromone flakes? What are they and how theyll do the trick in controlling moth population?
WALZ: Well, the pheromone is really a marvelous development – its the scent of a female moth, and the race or the kind of gypsy moth that we have here in North America, the females do not fly. And so the way that they connect with their mates, or potential mates, is by sending out a chemical signal that draws the males to them. This is called a pheromone. And this pheromone has been synthesized and placed into a little plastic flake probably no more than a 16th of an inch long or so, and this flake will emit, very slowly, the scent of the female moth. And so, by dispersing this scent throughout a forest is what happens, the males cannot locate the females, and they dont mate, and, as the song goes, theyre looking for love in all the wrong places.
CURWOOD: Now, how do the pheromone flakes get introduced to the male moth?
WALZ: Theyre actually flown over the woodland, by an airplane, and actually released just like you would with a spreader, like a crop duster kind of a plane, and they drop the flakes out and then they stick to the leaves and start working. Its a technology that works only on the leading edge, or whats called the front, because the populations of gypsy moths need to be rather low for the pheromone to actually work. If their populations are very high, the males can easily see the females, and once they see the female they dont need to use the scent anymore as their guide.
CURWOOD: How effective is this pheromone technique? What kind of results do you think youre getting?
WALZ: Well, as an example that weve used in prior years here in the state of Indiana, we had a situation in which we used it over about a 3,000 acre area, and in that particular area we dropped the counts from what were several thousands of moths in that area to a level where we only think we had 6 or 8 moths trapped that following year. So it worked out very well.
CURWOOD: Dr. Robert Walz is an entomologist for Indianas Department of Natural Resources in Indianapolis. Thanks for taking this time with me.
WALZ: Well thank you.
[MUSIC: Magnetic Fields, "100,000 Fireflies," WAYWARD BUS/DISTANCT PLASTIC TREES (Merge - 1995)]
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