Voracious leaf-eating caterpillars return to area trees

By Ryan Cornell

The creepy-crawlies are back.

With temperatures up and summer just around the corner, area residents might have noticed the annual return of caterpillars and other bugs sharing the yard.

A number of these insects, including the fall cankerworm, eastern tent caterpillar and gypsy moth, have reappeared to wreak havoc, not only on phobic humans but also local trees and forests.

According to Chris Asaro, forest health specialist at the Virginia Department of Forestry, cankerworms are one of the commonwealth’s most common nature defoliators — insects that strip leaves off trees or plants — and tend to prefer oak trees.

These caterpillars are often called inchworms or loopers for their method of scrunching up their bodies to move, and are usually colored light green.

He said Virginia has experienced “massive cankerworm outbreaks” in the past few years, while gypsy moths have hardly registered, though he said cankerworms are more of a nuisance pest to people moving into rural areas than an environmental concern.

“A lot of people are living where these cankerworms periodically erupt and they get upset because they have poop raining down on them and get covered in worms and silk,” he said.

The diet of eastern tent caterpillars is different, as they feed on the leaves of cherry trees and some ornamental apple trees. Although their population peaks in early spring, the distinctive tent-shaped webs they leave behind are proof of their presence.

Woodstock Tree Board Chairwoman Joan Comanor said gypsy moth caterpillars have stayed away from the town in recent years, but eastern tent caterpillars have proven to pose more of a challenge. She called them unsightly.

“Several places I go by and see the trees completely defoliated,” she said. “It’s always sad to see that from any of these pests like that.”

She advised homeowners to keep an eye on the caterpillars and to eliminate them “before they go back to their tents at night.”

Although the Tree Board doesn’t have any active programs to prevent the pests, she said members are observant and will report problems with trees that need attention. The board is currently working to increase its tree canopy from 22 percent to 30 percent by the year 2021 and has a scheduled tree planting along South Main Street on June 12. She said they try to diversify the tree varieties they plant.

“We’re only planting two or three of any given species,” Comanor said. “So if something does come along and is only attracted to a certain tree, we won’t lose a lot of them.”

Because the gypsy moth caterpillar isn’t native to Virginia like the other two insects, it’s considered an invasive species and areas such as the Shenandoah National Park and Fairfax and Prince William counties are focused on preventing their spread.

Rolf Gubler, a biologist at the park, said they spray an insecticidal bacterium called Bt — Bacillus thuringiensis — in spots limited to the Skyline Drive corridor and developed areas where they’re pervasive.

“With exotic species, whether they’re an insect species or an exotic disease, we’re mandated by law to reduce their impacts,” he said. “In the case of the gypsy moth, like the spot outbreak of 2007 to 2008, anywhere between 7,000 and 12,000 acres were defoliated. We’re trying to minimize the amount of defoliation in oak trees along Skyline Drive.”

Contact staff writer Ryan Cornell at 540-465-5137 ext. 164, or rcornell@nvdaily.com