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A full campground: Tent caterpillars having a good year

Photo

Photo by Dan Lassiter

The tent caterpillars have deposited egg sacks on the Dowd's siding.

Photo

Photo by Dan Lassiter

A tent caterpillar on the outside of one of the many tends in the trees near the Dowd home on Janesville's north side.

Photo

Photo by Dan Lassiter

A caterpillar tent in one of the trees behind the Dowd home on Janesville's north side.

JANESVILLE — Rachael Dowd’s shoes might have a place in the Entomologist’s Hall of Fame.

Dowd—retired schoolteacher, garden club member and all-around gentle soul—stepped on 2,000 eastern tent caterpillars in 24 days.

Where, exactly, did she come up with figure? Multiplying the square footage of her driveway by her shoe size? Paying neighborhood kids to add up the squash marks?

No. It’s something more prosaic.

“I counted,” Dowd said.

Yes, it’s been a good year for tent caterpillars.

The beasts are usually spotted after they’ve formed their trapezoid-shaped tents in crotches of trees.

Up close, the caterpillars are 2- to 2.5-inches long. They sport long white stripes down their backs and have iridescent blue dots along the sides of their bodies.

Very stylish, but a little iridescent blue goes a long way.

“Our driveway looked like a graveyard,” Dowd said.

Outbreaks of tent caterpillar weirdness have been reported all over the state, from Sauk County to the summer-cabin counties farther north.

“It’s one of those cyclical things,” explained Mary Ann Buenzow, Department of Natural Resources forester. “It’s usually about every ten years.”

The weather helped, too.

“We had a milder winter and a warmer spring,” Buenzow said. “They got started earlier than usual this year, but the good news is that they’ll be done earlier.”

Caterpillars spend their time eating tree leaves. Their favorites are wild cherry, choke cherry, apple and ornamental crabapples, but they’ll settle for hawthorn, maple, birch, box elder and a variety of other trees, according to the UW Extension.

Unless trees are already diseased or otherwise stressed, they’ll survive the defoliation with a second flush of leaves.

“It’s never too late to re-foliate,” Buenzow said with a laugh.

If you’re concerned about the damage, remove the caterpillar tents with rubber gloves or a stick and drop them into a bucket with water and a few drops of dish soap. Buenzow uses “a squirt” of soap in a five-gallon bucket.

Nothing stronger is needed.

Other treatments include applying an organic pesticide, Bacillus thuringiensis (Bt). But the product needs to be applied to the leaves, not the tents, so the treatment isn’t practical for larger trees.

And while it may be satisfying to burn the tents out of trees with propane torches or flaming sticks, don’t do it.

“It kills the cambium, the growing layer of the tree,” Buenzow said. “Probably the best thing to do is just to leave them in. They’ll be gone in a few weeks.”

After about six weeks of living in tree tents, the caterpillars transform into small moths that have a short lifespan and eat almost nothing, Buenzow said.

At the Dowd household, the caterpillars are beginning to beat a retreat.

Rachael and her husband, Jim, are happy to see them go. Now the couple can have their driveway, their trees and their fence garden back.

On the positive side, it’s made for an interesting spring.

“It was becoming a full-time job,” Rachael said of the caterpillar suppression effort. “And people wonder what retired people do all day.”