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Name: Pam V.
Status: other
Age: 50s
Location: N/A
Country: N/A
Date: Tuesday, May 07, 2002

I've checked your biology section but cannot find this problem. We are new to Illinois and all of a sudden our trees (does not seem to matter what kind) have what looks like dense spider webs in them. The webs are crawling with caterpillar-like bugs. Is this dangerous to our trees? Will they go away by themselves?

Sounds like "tent caterpillars". I suggest you cut the webs off and either burn them or dispose of them...but not in you yard compost a wooded area where they will continue their life cycle.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy

These are probably "tent caterpillars", which build their "tent" in the fork of a tree branch. They are voracious eaters and can defoliate a tree or ornamental shrub very quickly. I do not know if they are lethal to the tree/shrub, but certainly don't do them any good. There is a similar caterpillar (forgot the name) which is similar except they build their "tents" ON a branch and not in the FORK of a branch. You can find out a lot on the internet search the term: "tent caterpillar". I use the search engine . You can find a photo on the site: I think that physical removal plus an insecticide is recommended because the insecticide alone cannot penetrate the "tent".

Vince Calder


At this time of the year it likely you have one of the tent caterpillars. The easiest method of control is to go out at dusk with a glove and plastic bag and physically pull the tent from the tree (be careful to keep as many of the insects as possible, and place the tent into the plastic bag. You can then tie the bag closed and place it in the trash.

I have seen people do all sorts of crazy things, from burning the tent (and killing the branch) or cutting off entire branches. Sometimes the humans do more damage than the insects would. The method I suggest is safe for the humans and tree involved. Pruning off the affected branches is an option of the tent cannot be easily removed. Close to the ground you can use a hand pruner; stores like Home Depot sell pole pruners for out of reach pruning. As always do not use a pruner anywhere near electrical lines and be sure to maintain proper safety while using a ladder.

I you do not remove the tent, the caterpillars will leave the tent during daylight and eat leaves on adjacent branches. The caterpillars and tent will grow in size, and you will find waste matter from the insects inside the tent. I don't think one defoliation will kill the affected branch unless the tree is already weakened. This certainly is a visually unpleasant problem which as I mentioned is safely, easily rectified.

For more information contact your county local agricultural extension agent. Check the government listings of your phone book. Good luck!

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Ric Rupnik

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