Callaway County
Callaway County
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April 2000 |
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Eastern Tent Caterpillars Have Pitched Their Tents |
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As the larvae grow, the webbed tent is enlarged. During the day, the larvae leave the tent to feed on the foliage. As it exits the tent, each larva will spin a strand of silk as it travels, perhaps to help find its way back to the nest. The larvae remain in the tent during the night and on cloudy days. When mature, the larvae will leave the tent and search for a protected place where they can spin a rather large, thick, white cocoon around themselves and pupate. These cocoons can be found on the sides of trees, among the debris on the ground, on brush and weeds, fences, and even on sides of buildings. During late summer, the adult female will lay 200 to 300 eggs in bands around small twigs on the host tree. The eggs are held in place and covered by a varnish-like substance. The eggs do not hatch until the following spring, about the time the buds of the host tree begin to break open. The eastern tent caterpillar is a native pest that prefers wild cherry, apple, and crabapple. It will occasionally feed on forest and ornamental trees such as ash, birch, maple, oak, poplar, cherry, and plum. If it defoliates the first host tree, it will travel to adjacent trees or shrubs to feed. During most years, populations of eastern tent caterpillar are kept in check by cold winter weather, predators, and parasites. When populations reach a point where artificial control must be employed, the best non-chemical control is to destroy newly developing web nests. Removal of the tent cannot usually be done by pruning. The tents are often found on the fork of major limbs where pruning would not be good for the tree. However, during the night or on cloudy, overcast days when the caterpillars are in their tents, the tents can be scrapped off the trees and destroyed. Any caterpillars that are not destroyed will climb back up the tree. For larger infested trees, where it is impractical to destroy the nests, chemical control is often necessary. Chemical applications should be made as soon as the web nests first appear. Some insecticides that can provide control are certain formulations of diazinon, carbaryl, acephate, and Bacillus thuringiensis (Bt). Be sure to read the label on any pesticide. There are insecticides that are not labeled for use on fruit trees or certain other trees. One example is carbaryl, a.k.a. Sevin, which acts like a chemical fruit pruner on apples. Just a couple of other things to think about are: 1) large, older worms are harder to kill than small, younger ones; 2) if they are numerous, it may hard to tell if you are killing them since many other will take their place; and 3) if they are just crawling around, surface sprays may not be effective unless it gets on the worm or it is eaten. Information for this article is from Bruce Barrett, Extension Entomology, University of Missouri - Columbia 573-882-3446. Jim Jarman, Agronomy Specialist 573-642-0755.
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The nests (tents) of eastern tent caterpillar
have appeared in the forks or crotches of trees again. Three mild
winters in a row have allowed higher and higher numbers of eggs to
survive each successive year. Last summer, the light reddish brown moths
of the eastern tent caterpillar laid 200 to 300 eggs in shiny brown
masses that wrap around tree twigs. The mild winter allowed most of
these eggs to hatch. Tent caterpillar nests are found in the crotches of
trees in the spring, Webworms are found nests at the tips of branches in
the fall.
