The U.S. Forest Service is using ground-up caterpillars and another biological insecticide to target an infestation of tussock moths on national forests in the Pacific Northwest.
In a widespread outbreak in the 1970s, the moths defoliated trees across 700,000 acres in Oregon and Washington. The agency hopes that the caterpillar concoction, which carries a virus that kills only tussock moths, will suppress an outbreak this summer.
Forest officials say nine national forests in Oregon and Washington are vulnerable within the next two years. Eighty-five percent of their monitoring traps caught tussock moths in 1998 - up from 32 percent in 1994. By declaring the outbreak an emergency, Forest Service officials didn't need to wait 45 days before taking action. On June 15, the agency began spraying the Wallowa-Whitman and the Umatilla national forests - despite a lawsuit filed on June 2 by environmental groups. In their suit in district court, the seven conservation groups argued that the spray, TM-BioControl, has unknown effects on wildlife and humans.
"They claim the virus doesn't affect other moths," says Asante Riverwind, co-director of the Blue Mountains Biodiversity Project, "but (the Forest Service has) only tested it in controlled areas."
Next summer, after forest managers have run out of their limited TM-BioControl supply, they plan to spray Bt.k., Bacillus thuringiensis var. kurstaki, a naturally occurring bacteria that affects all moths and butterflies. Conservationists fear that Bt.k. will eliminate rare species of moths and butterflies.
Riverwind adds that tussock moths are a regular and natural part of the forest. "Forest ecosystems," he says, "have handled moth outbreak populations for thousands of years."