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

Frequently Asked Questions

Topic:	Caterpillars, tent caterpillars
Question:	What is the best way to get rid of tent caterpillars? Which pesticide is best?
Answer:	There are several good treatments for tent caterpillars and other caterpillars. If possible, it's best to control caterpillars without resorting to stronger chemical pesticides. This is because many pesticides are also toxic to the beneficial insects that normally keep tent caterpillars and others under control. With tent caterpillars tents are built in the crotches of branches. These can be torn open and sprayed with a low toxicity insecticidal soap or oil spray. The fall webworm, another tent-making caterpillar, typically builds its webs over the tips of tree branches. On smaller trees these caterpillars can be pruned or shaken out of the tree. Place a garbage can or other receptacle under the web before cutting or shaking. Most or all of an infestation can be removed on some trees. Where webs cannot be pruned or shaken out, sprays containing the bacterial insecticide Bacillus thuringiensis can be used. Bt sprays, as they are called, are most effective on smaller caterpillars. As caterpillars exceed ½ to 1 inch in length, they become more tolerant of Bt sprays and a stronger treatment may be necessary. Should damage to your tree become unacceptable, and Bt or the mechanical methods are impractical, most insecticides labeled for caterpillar control are very effective. Be sure to follow label instructions. Products containing permethrin, esfenvalerate, bifenthrin and cyfluthrin are highly toxic to caterpillars and provide excellent control for up to two weeks. Pesticides can quickly reduce or eliminate a caterpillar outbreak and preserve the aesthetic beauty of a tree. But are pesticides necessary to protect your tree's health? Trees and other deciduous woody plants can withstand considerable defoliation without any substantial effect on their growth and vigor. A general rule of thumb is that trees in the spring can withstand 20% defoliation, in the summer 40% defoliation, and in the fall almost complete defoliation with little harm to the tree. In many cases the best thing to do is leave the tree alone. Most Texas trees learned to battle caterpillars a long time ago. And they will be here long after we are gone, with or without our assistance.
Related Link:	http://insects.tamu.edu/cimg294.html
Related Link:	http://insects.tamu.edu/extension/bulletins/l-1637.html
Image Link: **
Response by:	Michael Merchant, Ph.D.
Title:	Professor and Extension Specialist
** Most of the Related Links above also contain images.

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