Question
The webworms are invading Dallas and a month or two earlier than last year.  I used a chemical around the tree roots but I can't find the brand.  It was supposed to be systemic to the tree and the worms were supposed to eat the bark and fall off and die. It was so late in the season when I found the insecticide I don't know if they were reduced in population because it was August or because of the chemical.  They cover our cars and I found white moths all over my house and covering my porch after I thought I got rid of the webworm.  I wanted to do something "green" so I sprayed dishwashing soap all over my porch but to no avail.  Any suggestions?  Thanks!

Answer
There are generally two types of "webworms" eastern tent caterpillar and fall webworm. The Eastern tent caterpillar is on trees in the spring and the tent (web) is normally near the trunk of the tree in a crouch. The Fall web worm is in the late summer or Fall and the tent  are on the outer foliage on a limb.
If there are tent snow it is Eastern Tent caterpillar.
  Adult tent caterpillar moths have a 1-inch wingspread and are brown and yellowish with two diagonal markings on the forewings. Caterpillars (larvae) grow to over 1-?inches long. They are brightly colored with long hairs on their bodies, mostly along the sides and marked with a solid white line down the center of the back. Other colors may vary but solid or broken lines of blue, yellow and black are also present. Larvae form a dense silken web usually in the crotch of small limbs which is used as a refuge at night and during rainy spells. The tent is expanded as the caterpillars grow.

The winter is spent as a hard mass of eggs that encircle a twig. Larvae hatch in early spring just as the plants leaf out (mid-February to mid-March). Caterpillars develop through several stages (instars) before leaving the host plant to pupate in a cocoon. There is only one generation per year of tent caterpillars so all activity is usually over by May or June.

Natural enemies play an important role in reducing eastern tent caterpillar numbers in most years. Caterpillars are frequently parasitized by various tiny braconid, ichneumonid, and chalcid wasps. Several predators and a few diseases also help to regulate their populations. This, in part, accounts for the fluctuating population levels from year to year.
Prevention and early control is important. Removal and destruction of the egg masses from ornamentals and fruit trees during winter greatly reduces the problem next spring. In the early spring, small tents can be removed and destroyed by hand. Larger tents may be pruned out and destroyed or removed by winding the nest upon the end of a stick. Burning the tents out with a torch is not recommended since this can easily damage the tree.
Young caterpillars can be killed by applying an insecticide containing Bacillus thuringiensis var kurstaki. Other insecticides include carbaryl, methoxychlor, and malathion. Larvae within the tents are protected beneath the webbing and are more difficult to kill with an insecticide.

A systemic insecticide containing bifenthrin can be applied to the soil and when the caterpillar feeds on the leaves it is killed.