The variable oakleaf caterpillar returns: noisy, messy but harmless

Showing up in southwest Arkansas counties

As scourges go, the return of the variable oakleaf caterpillar is pretty mild. But they do have a way of getting your attention.

Cooperative Extension Service agents throughout several southwestern Arkansas counties, including Polk, Pike, Clark and others, began receiving calls earlier this week -- concern bordering on panic as large oak trees throughout the region began losing their leaves, practically overnight.

“I’ve probably received 40 calls in the last two days,” said Allen Bates, Garland County agricultural agent, on September 20. “The caterpillars are infesting a lot of oak trees, here in Hot Springs -- the county courthouse called me up there this morning.”

The variable oak leaf caterpillar -- so called because its color can vary widely from one insect to the next -- is now embarked on its annual feeding frenzy throughout much of the Southern Plains, gnawing its way through oak leaves, and depositing its droppings on sidewalks, porches and vehicles below. When the caterpillar is in sufficient concentrations, the sound of this process can sometimes be mistaken for rainfall.

But it’s not.

Tamara Walkingstick, Associate Professor of Forest Resources at the University of Arkansas System Division of Agriculture and Associate Center Director of the Arkansas Forest Resources Center, said the caterpillars -- a native insect to the region -- typically surge when trees are already going dormant for the year, and are an important link in the ecological chain.

“There are a couple of different bird species that rely upon these insects for food, including the pileated woodpecker and blue jays,” Walkingstick said. “So they’re not beneficial to the trees, but they are beneficial to the other predators that utilize these insects. They’re an important food source.”

The caterpillar’s other natural predators include parasites, ground beetles and stinkbugs.

While the caterpillar’s droppings may stain surfaces below, they pose no apparent health risks to humans or pets. Walkingstick said spraying insecticide on affected trees is both unnecessary and logistically impractical, given the height of many oaks.

“People want to spray things, I know,” Walkingstick said. “But look: it’s going to rain.”

Within a few weeks, the last of the insects will have fallen from the trees to the ground, where they naturally overwinter under the leaf litter, offering concerned citizens a chance to exert a modicum of control.

“It’s a good opportunity to reduce the local insect population by sweeping up the leaves and disposing of them,” Walkingstick said.

To learn about native insects, contact your local Cooperative Extension Service agent or visit www.uaex.edu.

TAGS: Management
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