Fungus routs gypsy moth outbreak.

Fungus routs gypsy moth outbreak

People in the eastern United States go to great lengths to prevent gypsy moth caterpillars from devouring forests and favorite shade trees. They sic bacteria and viruses on them; drop planeloads of pesticides on them; lure them, drown them, squash them -- and curse them. Failing these attempts, people may soon have a fungus to help fight the pests.

Last summer, the fungus Entomophaga maimaiga, which efficiently checks gypsy moths in its native Japan, unexpectedly proliferated in the northeastern United States. It slaughtered gypsy moths in droves, producing their first known massive fungus-induced die-off in North America, according to insect pathologist Ann E. Hajek of the Boyce Thompson Institute for Plant Research in Ithaca, N.Y.

This past spring, Hajek tested whether scientists could deliberately use the fungus in the wild to induce gypsy moth die-offs. She seeded a fungus-free woodlot in Ithaca with E. maimaiga spores from some of last year's battlegrounds. One month later, while caterpillars swarmed in untreated plots, fungus-ridden corpses littered tree trunks in her treated plots. Hajek estimates the fungus vanquished up to 85 percent of the leaf-gobbling pests.

Though Hajek foresees commercially produced batches of E. maimaiga someday bolstering the forester's and homeowner's arsenal against gypsy moths, entomologist Ralph E. Webb of the USDA's Agricultural Research Service in Beltsville, Md., remains wary. E. maimaiga was intentionally released against the moths in Massachusetts 80 years ago, yet it wasn't noticed again until 1989's unusually heavy spring rainfall. "In a dry year," Webb says, "the fungus would fall flat on its face."

Nevertheless, under less soggy conditions this year, researchers in several northeastern states are again attributing massive caterpillar die-offs -- of up to 90 percent -- to the suddenly conspicuous Japanese fungus.