Environment : Germany’s Just a Snack for Millions of Ravenous Caterpillars : The hairy hordes have munched their way across the country this summer, leaving gardens and forests bare and residents hysterical. Damage could run into the millions.

It began, Karl Frank now recalls, with a loud crunching sound.

“Like someone eating a big salad,” he said.

The salad turned out to be his back yard, which turned out to be a mere between-course snack for millions of gypsy moth caterpillars munching their way across Germany this summer, leaving entire forests as silent and bare as a winter wood.

Damage is still being assessed, but it is expected to easily reach millions of dollars as the ravenous caterpillars devour not only their customary diet of oak leaves but fruit trees, vegetable gardens and even grass as well. Residents are also filing claims to have houses repainted because of the brown slime covering walls the creatures have climbed.

“The ground was carpeted with caterpillars, and you couldn’t go walking in the woods because it was raining caterpillars,” said Alfred Schoepplein, forester in this Bavarian town that was hardest-hit by the plague. Most of the caterpillars have now entered the pupa stage and will re-emerge later in the summer as harmless moths.

Residents living on the fringe of the bald forest fled town as the hairy hordes inched their way up the sides of houses. Frank counted 120 of the two-inch-long critters on a single brick of his back wall.

The caterpillars covered windows and wormed their way inside houses, where, Mayor Emil Daeschner recalled with a shudder, “they fell off the ceiling while people were sleeping.”

“Small children were hysterical,” added Frank, whose neighbors decamped until the worst of the invasion was over.

Environmentalists and community officials also grew hysterical as the plague touched off a debate over the use of pesticides in nature preserves such as the formerly green forest on the hills above Ebelsbach. Rare orchids blooming in the preserve were also eaten by the pests, and their recovery is uncertain.

By the time ecologists were willing to permit any spraying, indignant foresters charge, it was too late, and the nature preserve was stripped bare.

“The caterpillars move incredibly fast,” said Schoepplein. “They can eat a big tree in three days, every last leaf.”

Volunteer firefighters were called in to fight the Ebelsbach invaders, digging ditches at the forest rim, lining them with plastic and filling them with a mixture of water and pesticide to stop the onslaught as the army made its way into residential areas.

Twice a day, they had to empty the ditches of caterpillars.

“They filled 80 garbage cans,” Mayor Daeschner said. “Each can could hold 50 liters (about 13 gallons). Then we would burn the caterpillars.”

The unprecedented plague apparently resulted from several mild winters and an unseasonable heat wave in the early spring, when a late frost normally kills off most of the 500 to 800 eggs typically laid by each gypsy moth.

This year’s population boom means even more eggs next year--and, Germans worry, even more damage. Trees are thought to easily survive one attack, but experts are wondering whether a second wave would prove devastating. Unless they sprout new leaves quickly, they said, the trees are unable to get oxygen and suffocate.

The caterpillar chow-down also has a domino effect.

“Not a single bird can be heard chirping in our forest right now,” Daeschner said. “Because the trees are bare and provide no cover, the birds have left, abandoning their nests and their young.”

Only the cuckoo bird and a type of beetle eat the gypsy moth caterpillars, and the numbers this year were far too great for natural predators to control.

Deer and small game also have fled the naked woods.

In the Franconia region, the arguments over turning to biological warfare--a virus, a bacterial spray or a hormone that would block development of the caterpillars--became “laughable,” said Reiner Stitzinger, a director in the regional forestry department in Ansbach.

The hormone isn’t poisonous, Stitzinger said. Under protest by the environmentalist Greens and opposition Social Democratic parties, helicopters bombarded over 4,000 infested acres with the hormone.

“We had to do it under public pressure,” Stitzinger said, adding that a nature preserve that is home to rare butterflies was not sprayed.

Private property owners were allowed to spray in some circumstances, but it was often too late, since experts say the gypsy moth is best attacked before the eggs hatch into caterpillars, in May or early spring.

By the time you hear crunching, they say, it’s too late.

“Now everyone’s pointing fingers,” said Stitzinger. “Some of the ecologists are sticking by the opinion that nature should be allowed to run its course.” Those who advocate spraying are accused of “being in bed with big industry,” he said.

The gypsy moths, once they emerge from their chrysalides in a few weeks, are considered harmless.

But this year brought not only the gypsy moth caterpillars but another oak-eating variety as well, whose hair is poisonous and triggered severe allergic reactions in about 100 people, doctors reported.

“You don’t necessarily have to even touch them,” said Dr. Beate Buer-Weber of the public health offices in Neustadt an der Aisch. “It’s enough just to sit under a tree where they are. The little hairs can fly through the wind and you can inhale them.”

Although not life-threatening, the caterpillars can cause rashes, coughing and even respiratory problems.

“Personally, though, I wouldn’t spray,” Buer-Weber said, “because I believe nature will help itself.”

That’s cold comfort right now to Karl Frank, whose 60 fruit trees were being eaten bare by the caterpillars until strips of treated tape on the trunks stopped them.

“It was roasting outside, but we didn’t dare open our windows,” Frank said. “I’m against spraying in principle, but that forest should have been sprayed.”

In the scenic Ahr Valley, the caterpillars covered a train track running through a stricken area, “and every hour there was caterpillar mass murder,” said resident Helge Seel. “They were regularly squished. It looked really awful.”

Times researcher Reane Oppl in Bonn also contributed to this story.