sealPurdue News

April 8, 2003

Caterpillars pitching their tents in Hoosier trees

WEST LAFAYETTE, Ind. – A Purdue University entomologist said the eastern tent caterpillars reappearing in Indiana trees this year are more of a hassle than a problem. Last year, the caterpillars caused severe defoliation of flowering trees in much of southwestern Indiana.

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Cliff Sadof, who studies insect problems in ornamental shrubs and trees, said the caterpillars generally don't pose a threat to tree health, they're just a nuisance to homeowners. However, they do eat the first flush of leaves and will slow the growth of trees in addition to building unsightly webs. They inhabit all of Indiana, although they've been more of a problem in the southern half of the state.

That's bad news for homeowners who prefer that their trees keep their leaves and remain free of the caterpillars' webs. But Sadof said homeowners should take heart.

"This insect has some peculiar habits that make it relatively easy to control," he said.

The caterpillars are early season pests, showing up in early to mid-April. They begin feeding just as leaves begin to break bud and they form tentlike webs in the crotches of trees. Sadof said it's those tents that make the caterpillars easy to control.

"Caterpillars remain in the tents during the day to avoid being eaten by birds," he said. "They crawl out at night to feed on leaves. If you can reach the webs you can remove the caterpillars while they spend the day inside."

Sadof suggested dropping the webs into a bucket of soapy water or stepping on them to kill the caterpillars. It takes about five tablespoons of dish soap per gallon of water to make a lethal dose for caterpillars. The soapy water isn't a toxic waste product so it can be discarded onto the ground or down a toilet, he said. However, Sadof cautioned homeowners who have large numbers of the caterpillars to dispose of them in a compost heap or trash bin.

If the caterpillars' tents are hard to reach or too numerous, two biological pesticides can be used. Sadof said Spinosad (Fertilome Borer, Bagworm, Leafminer and Tent Caterpillar Spray) and Bacillus thuringiensis could kill caterpillars.

"Both of those materials are easy on the beneficial insects that control other pests and contribute to pollination," Sadof said. "Although acephate, carbaryl and pyrethroid insecticides can kill caterpillars, they also kill beneficial insects that prevent mites and scales from becoming a problem."

This isn't the first year Hoosier homeowners have dealt with the eastern tent caterpillar.

Larry Caplan, an Extension educator in Vanderburgh County has seen the caterpillars quite a bit.

"I've already come across a couple of tents this month," he said. "I think I'll see even more as the leaves start to appear on trees."

Although the full extent of this year's caterpillar invasion isn't known, Sadof said he thinks they're likely to reappear in large numbers.

"For the past two years crabapples and other flowering fruit trees in much of Indiana have been defoliated by the eastern tent caterpillar. There is a fairly good chance that they will continue to be a problem this year," he said.

Writer: Kay Hostetler, (765) 494-6682,

Sources: Cliff Sadof, (765) 494-5983,

Larry Caplan, (812) 435-5287,

Ag Communications: (765) 494-2722; Beth Forbes,;


Related Web sites:
Tent caterpillar fact sheet


The eastern tent caterpillar will likely make its way into Indiana trees again this spring. The caterpillars are dark in color with a white stripe on their backs and may grow up to 2 inches in length. (Photo/Cliff Sadof)

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