Frequently Asked Questions About Insects - Department of Entomology at Texas A&M University

Frequently Asked Questions

Topic:	Caterpillars, on post oak
Question:	I have a big post oak tree in the backyard with a deck around it. I have noticed a lot of tiny droppings (I assume that's what they are) on the deck under the tree but really haven't seen any kind of pest. I assume this might be the work of caterpillars in the tree. Can you advise? Do I need to spray the tree or is the problem short-lived?
Answer:	There is a whole collection of caterpillars on oaks in early spring. They can be annoying, but they probably have little effect on the tree. I would try to ignore them for about three weeks, if you can. If they are really thick they can defoliate some trees. However, as long as there is moisture and the tree is not stressed, the tree will leaf out again. If you decide to spray you should do so right away before the caterpillars get big. They do most of the feeding when they are large. The Bacillus thuringiensis products (Dipel, Thuricide, Worm Killer, etc.) are the safest around the home. You could also use carbaryl (Sevin), diazinon, or several other products. When the trees are large you cannot get the product up the tree very high, so you might have to hire a tree service or a pest control operator. A hose-on sprayer probably reaches as high as any sprayer that homeowners have available.
Related Link:	http://insects.tamu.edu/extension/publications/
Related Link:
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Response by:	John A. Jackman, Ph.D.
Title:	Professor and Extension Specialist
** Most of the Related Links above also contain images.

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