Question
My daughter who lives in Texas is having a problem with tent caterpillars on her crepe myrtles......is there an effective spray for this problem?

Answer
Sounds like Fall webworm.  The fall webworm is a native of North America and Mexico and attacks at least 88 species of trees, and shrubs, ornamentals and annual plants. It is distributed throughout most of the United States and Canada.

Fall webworms weave their webs on the ends of the branches to feed on foliage and are protected by the silken tent. The young scrape and eat upper leaf surfaces, leaving brown husks behind. As they grow, they eat everything except the thickest veins. The tent becomes enlarged, as the webworms grow larger.

The fall webworm tents are ugly but they seldom kill mature trees and plants. Most plants will tolerate leaf loss after midsummer and will come back the following year. There are several methods for control of the webworms. (1) A number of native insects and animals prey on webworms. The webs can be opened with a stick, rake or stream of water to allow the natural predators inside. (2) Remove tents by pruning the end of the branch and destroy. (3) Though seldom required, several insecticides can be used. Microbial Bt will attack small caterpillars or Diazinon, Sevin or Orthene for larger tents. It helps to break open the web and then spray the insecticidee inot the web and nearby foliage.

Another thing that can be done on tall tree is to spray the trunk with Orthene and when the caterpillars crawl down the trunk to pupate they are killed.

Here is a web link to information on Fall Webworms and pictures of the webs so you can make sure this is what you have. http://www.hgtv.com/hgtv/gl_diseases_pests_insects/article/0,1785,HGTV_3580_1372...