Why Are There So Many Web Worms In The Trees?

Have you ever noticed all the web worms in the trees? John Boyle with the Citizen-Times answers this question about web worms.

Question: I've gotten several readers asking me about web worms, particularly out in Haywood and Jackson counties, where they're everywhere. Some of the questions include: Is there any way to get rid of them besides torching them? Does the state or country have any plans to eradicate them?  I've never seen the volume quite this thick. Is this normal or is something unusual going on? How much damage can the caterpillars do to the trees? Can you find out any information on the life cycle of this species?

My answer: I just have a vision in my mind of a guy standing under an immense, flaming tree, saying to his wife, "Now Honey, nobody would've thought those bugs could make that big a blaze. Call the fire department."

Real answer: First of all, no need to burn them out. Really. Don't do that. Drop the flame thrower.

These critters are called "fall web worms," said Sarah Scott, horticulture agent for the Haywood County Cooperative Extension Service. They're often confused with tent caterpillars or bag worms, but they are a different species.

"This is the time of year we seem to notice them," Scott said, adding that they actually emerge in the spring. "It's a small moth that emerges around April."

As soon as they emerge, they begin mating and laying eggs on the underside of trees leaves. It takes about seven days for the newbies to come out, and then they start building a web and feeding on the tree's foliage, although at this point we don't usually notice them.

"After several more weeks, they get larger and evolve into moths again," Scott said. "This is the later, second generation we see. They're heavier feeders and their webs are a lot larger."

While they do make webs on the tips of branches, and those webs get to be two-three feet long, Scott stressed that they're "not doing permanent damage to the trees."

"They only eat the foliage," she said. "They don't eat the buds, so it doesn't affect that next year's buds."

And, as the readers noticed, they are worse this year, and that's probably because we've had two mild winters in a row.

"We need that cold weather consistently to lower all of the pest populations," Scott said.

Jim Costa, a biology professor at Western Carolina University and director of the Highlands Biological Station, added that the insects are cyclical in their population booms and busts.

"It just takes one really bad cold snap to maybe kill that first generation, and then they go bust," Costa said.

The populations do seem the largest in Haywood and Jackson counties, Costa said, where some of the colonies have create so many and such large nests that they seem to have merged into "one giant super colony."

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