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.”
This article appeared in the print edition of the magazine with the headline Caterpillar concoction causes concern.
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