Bagworms Hit Trees

NEW BREMEN — After having to remove multiple village trees last summer, New Bremen is cautioning its residents to be on the lookout for bagworms.

“Last year, we had two areas where they were really bad, one by the tennis courts by the pool and we also had them in the industrial park,” New Bremen Parks Foreman Ron Tontrup said. “Around the tennis courts, there were three arborvitae that we had to dig out and replace. They just kill the trees.”

According to the Ohio Department of Natural Resources Division of Wildlife, bagworms can be serious pests, especially in landscapes.

“Beginning in late May through mid-June, larvae of this native moth feed on arborvitae, junipers, pines, spruces and many deciduous trees,” ODNR’s Division of Wildlife’s website notes. “Larvae build loose, silken bags, which cover their entire bodies. Bags are camouflaged with pieces of plant material and may be mistaken for natural parts of the tree.”

Females do not look like moths — there are no wings, legs, antennae, eyes or mouthparts — and remain in silken bags throughout their entire lives.  When larvae are fully grown, their protective bag is 1.0 to 1.5 inches long. In late summer, male moths (black, with nearly clear wings approximately 1 inch across), emerge from their bags after pupation. One generation occurs per year.

“We’ve had them off and on for a few years,” Tontrup said. “Last year was the first year they did damage — we had five trees total that we had to dig out and throw away.”

He noted the village recently sprayed for the pests in a few areas.

“There were a group of the problem areas and other areas that we felt we wanted to project,” Tontrup said. “Typically, right now is when you spray for them. They’ll show up in mid-to-late summer, and there’s a small window that of time that you have to spray for them.”

He noted the village wasn’t able to spray beforehand last summer.

“After last year, I said we’ve got to do something — I did the research and council gave me the OK to go ahead and said let’s do it,” he said.

Once the pests are on the trees, there’s not much else to do, Tontrup added.

“Once they’re on the trees, it doesn’t do you a lot of good to spray,” he said. “There’s some stuff you can spray on them, which will slow down their speed, but it won’t stop them or kill them.”

Tontrup noted the trees the bagworms killed last year were arborvitae and pine trees.

“If there’s enough of them on there, they’ll destroy it,” he said. “They get onto other trees, but that’s what we’ve seen them on.”

Besides looking for the larvae, there aren’t many signs of the bagworms.

“When you see a brown bag, that’s it, you’ve got them,” Tontrup said. “There isn’t usually a sign before that, other than leaves falling off the trees or things like that.”

He noted the only way to kill the bagworms is to burn them.

“When you get them on a tree, you can pick them off, but you have to burn them,” he said. “You can’t throw them away in a trash can or they’ll be out of there in no time.”