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Unweaving the Webworm's Web

No, your tree is not infested with a blood-sucking spider on the tips of its branches. No, your tree is not making a canopy full of cotton candy for the fall festival. However, it is infested with a crawling critter known as the fall webworm— mainly because it’s a webworm that’s primarily observed during the fall. Clever, right?

Fall webworms make their tent-like structures in the tips of over 90 species of trees.

Fall webworm, or Hyphantria cunea, as it is less commonly known, is the larval form of a moth— a pearly white, brown spotted, beautiful creature of the sky! Its juvenile form, however, isn’t so cute. They kind of remind you of something crawling around in the bottom of the trash can on a hot day— its black and yellow segmented body exploding with thin white hairs, like the “peach fuzz” on a teenage boy’s chin.

The female moth lays her eggs on the leaves of more than ninety types of trees, including cherry, birch, pecan, and hickory, some time around the middle of June. About seven days later, the young larvae hatch and begin to feast. And feast they do! They being to chew and bite and rip your tree’s leaves to pieces as they spin their silky webs on the tips of tree branches— leaving behind damaged leaves, dead leaves and fecal droppings. Yes, fecal droppings. Makes the cotton candy idea a little less appealing, doesn’t it?

Next, the larvae crawl out of their web-like lair and pupate on or in the ground. That doesn’t mean what it sounds like, I promise. By pupating, I mean that they form cocoons and later will emerge as the beautiful white moth I mentioned earlier. In addition to all this, fall webworm can produce up to two generations in a year!

So, the question you’ve been asking since you read the title: is this pest going to kill my tree? In short, no. Your tree is safe. It is an unsightly issue, cosmetically speaking, but the tree can handle the small amount of damage that the webworms cause.

Fall webworms leave behind skeletonized leaves and fecal droppings. Yummy.

If you must, you could remove the tents that are close enough to the ground and reachable with loppers or a pole saw. As for the ones closer to the heavens, there are over 50 predators and 36 parasites waiting to devour the little guys. So the way I see it, by leaving the webworms, you’re just doing your part to feed nature— and instead, you can just sit back, relax, and drink a glass of sweet tea.

However, if the tree is young and nearly completely covered in webworm tents, that might be cause for concern. Young trees that are infested with fall webworms could become weakened and its growth reduced. If this is your case, feel free to remove all of the tents and use a little biological control.

By biological control, I mean find yourself an active little munchkin to stomp around and dance the life out of the little boogers. For tents that can’t be reached, the application of the bacteria BT— or less commonly known as Bacillus thuringiensis— into the higher parts of the plant can help to keep webworm numbers low. This part’s really cool. You see, the webworm will actually consume the BT and the BT will give a nasty tummy ache to the worm until it dies...slowly…and painfully. For those of you who are against all forms of chemical sprays, this is natural and organic control at its best! No amount of Rolaids could help that kind of gastric imbalance.

Over 50 predators and about 36 parasites consider fall webworm as a food source.

But again, eliminating fall webworms in the landscape is not necessary. Despite their benign nature, they are a bit of an aesthetic party pooper. They will come and go year to year, gracing you with their silky tents some years more than others. You might even miss them during their “low” years. Regardless, I will leave you with this stern warning:

Never, under any circumstance, should you ever light a torch on the end of a stick and burn the tents while they still remain within the tree. Never!

Now that I think about it, I probably shouldn’t have even mentioned that and given you the idea. Oops.

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