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alternatives to pesticides - bugs/pests - Tent Caterpillars


tent caterpillars

Actual size: Up to 3”

These caterpillars spin the silky white tents that cover the tips of branches. They damage plants by eating foliage as it emerges. They eat leaves off many deciduous trees and shrubs, especially walnut, alder, willow, fruit trees and roses. If a tent has been on a branch for awhile, chances are some caterpillars are fully grown (up to 3”) and have left the tent to select a site to spin cocoons. After about two weeks, adult moths emerge, mate, lay eggs and die. The eggs are laid in a foam-like band around small twigs or branches of the host tree where they hibernate over the winter. When new leaves begin to appear in the spring, the eggs hatch.

Physical control
Consider tolerating a few tents. These caterpillars are native insects and are controlled in the long term by natural factors.
Prune - Prune out branches containing tents in particularly valued trees or those with heavy infestations. Prune early in the morning or in the evening when caterpillars are in their tents. Put tents in a sealed paper bag in the garbage.
Remove - During the winter, examine branches and rub off egg masses that appear as hardened gray or brown frothy material, somewhat similar to Styrofoam. Egg masses are usually 1/2” long bands surrounding twigs. Deposit in a bag, seal it and place it in the trash.

Biological control
Tachinid Flies - Tachinid flies deposit white eggs, natural parasites, in visible rows on the caterpillars’ backs. If you look closely at the caterpillars and see these eggs, natural controls are working.
Bacillus thuringiensis  - Bacillus thuringiensis (Bt) is a bacteria used to control certain pest larvae, primarily caterpillars. Bt is not toxic to humans or other mammals but will kill butterfly (“friendly”) caterpillars as well as the problem ones. The bacterium kills larvae by interfering with digestion. To be effective, Bt must be sprayed so that it thoroughly coats the surface of leaves; Bt lasts on leaf surfaces five to seven days.  Bt is a stomach poison so it must be ingested to be effective. There are many strains of Bt commercially available now, including strains for controlling mosquito and beetle larvae. If you use Bt, use it only on the affected plant and follow label directions.



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