Munch Gypsy, Crunch Gypsy

By Frederic Golden

In a cyclical battle, bugs are again triumphant over trees

Untold numbers of trees defoliated, stripped naked of all leaves. Squishy little creatures hanging from branches, crawling over the sides of houses, creating a sickly goo on roads. People rushing to their doctors with rashes on hands, faces, anywhere they may have brushed against the little pests. Neighbors arguing angrily about whether to resort to risky chemicals. Noisy town meetings. Anguished editorials in newspapers.

Episodes from a late-night horror flick? Not at all. More like cinema verite. Once again, the Northeast has been infested by gypsy-moth caterpillars in record numbers. Last year the bugs chomped so voraciously through more than 5 million acres of woodland that the usually lush summer landscape looked as leafless as in late fall. This year's damage, patchily extending from northern Maine to Maryland and beyond, is far worse: an estimated 11 million acres of forest, an area larger than all of Massachusetts, Connecticut and Rhode Island.

Only 2 in. to 3 in. long when fully grown, the gypsy-moth caterpillar looks harmless enough: a brownish, multilegged strip of fur with telltale pairs of red and blue spots running down its back. But looks are deceptive. Ever since 1869, when it was inadvertently turned loose in Massachusetts by a misguided French naturalist who wanted to cross the European gypsy with the silkworm to produce a disease-resistant hybrid that would eat virtually anything, it has been munching its way across the Northeast. As many as 30,000 caterpillars can infest a single tree, and each of them can consume five or ten small leaves a day. They seem especially partial to the majestic oak but also eat fruit trees like apple and cherry, the maple and, alas, the already imperiled elm. If nothing else is available, they will nibble away at spruce, hardy pines and hemlocks, even shrubs--more than 500 species in all.

The feast begins in late April or May, when the caterpillars first emerge from their eggs. As they finish off one tree, they swing easily to another on silken threads they secrete. Their vagabond life accounts for the name gypsy. Millions can infest a small wooded patch. As they crunch, dropping excrement and half-eaten leaves, they sound like steady rain. Some homeowners complain that the noise actually keeps them awake. The caterpillars crawl up walls, spread over driveways, drop into plates and glasses at backyard barbecues. Last month Massachusetts officials got a call from a badly flustered woman. So many caterpillars had swarmed across her front door, she said, that she could not get in.

After molting for the last time, in late June and early July, the caterpillars spin the flimsiest of cocoons and harden into shell-like pupae, to emerge a week or two later as full-grown moths. Gypsy moths themselves do not eat. But each female lays velvety, tan masses of 100 to 1,000 eggs on tree trunks and buildings, on the undersides of cars, trucks and trailers, in carefully stacked woodpiles. Lighter colored and larger than the male, the female does not fly but attracts the male with a powerful chemical sex lure. By August both parents will have died, but the hardy eggs will survive through the winter, hatching in the spring and starting anew the devastating cycle.

After the first big outbreak, in Medford. Mass., in the late 19th century, New Englanders began battling the gypsy moth by putting out arsenic, soaking egg masses in creosote, burning down whole trees. But the bugs kept spreading. Wafted by winds, hitchhiking on cars and campers, they slowly migrated to at least 21 states, including Florida and California, although so far only pockets of serious infestation have occurred west or south of West Virginia. In the 1950s, scientists thought they finally had the moths under control with DDT. But the pesticide caused so much ecological havoc, including the death of some of the birds and rodents that are the moth's natural enemies, that DDT has been banned from general use.

Entomologists agree that the moths can never be entirely eliminated. But containment may be possible. Early in the larval stage, when the caterpillars are still small and vulnerable, shorter-lived, milder pesticides like Sevin are useful, though Sevin also kills bees, which are needed for pollinating many fruits and flowers.

Warns Cornell University Entomologist Warren Johnson: '"By the time you see caterpillars greater than one-half inch in length, the time has passed for the most effective insecticide application." At that stage, however, a simpler tactic may help: encircling tree trunks with sticky bands that trap the caterpillars as they scurry up or down. One difficulty: as the bands become overloaded, the caterpillars evade capture by clambering over the bodies of their trapped brethren.

Lately, subtler forms of warfare have been introduced, including sprays that contain Bt (Bacillus thuringiensis), a bacterium that kills various moth and butterfly larvae. It, too, should be applied early. Another new experimental spray spreads a virus that afflicts the gypsies with fatal wilt disease, so called because the dying caterpillar shrivels into a kind of inverted-V shape. More diabolical are traps scented with sex lures to attract male moths. Scientists have also been distributing different types of insects--wasps, flies, beetles--that prey on gypsy moths at various stages in their life cycle.

Despite all this lethal ingenuity, the only really good news from the bug battlefront is that most healthy trees can survive two or three onslaughts. Indeed, foresters like to point out that the moths often strengthen the woodland by eliminating sickly specimens. But such Darwinian reassurances are little comfort to suburbanites worried about a favorite elm or oak. By now, about all they can do is keep the tree as healthy as possible --faithful watering and feeding help --gather up and destroy every clutch of moth eggs in sight, and wait until next year. --By Frederic Golden. Reported by Anne Moffat/Ithaca and Sara White/Boston

With reporting by Anne Moffat, Sara White

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