EASTERN TENT CATERPILLAR

This pest is commonly found on fruit trees and ornamentals including Crabapples, Hawthorns, Cherry and Plum. The caterpillar larvae begin to hatch as the leaves on crabapple trees start to emerge - usually in late March. If not successfully thwarted, the caterpillars will feed on the leaves causing defoliation which can weaken trees over time.

Often, the pest is not observed until the telltale white tents or webs that have been formed in the crotches of branches are spotted. It is important to act as quickly as possible to control the pest. Early on, tents may be as small as 1 inch long, and the "worms" themselves about a quarter-inch. The protective tents expand quickly and mature caterpillars can grow to 2 inches. The become quite hairy and have an identifiable whitish-yellow stripe down their back. Once the larvae have grown beyond an inch and a half, they become invulnerable to chemical control. The most effective control is through hand removal of caterpillars and tents as early as possible. Often a simple pressurized water spray can solve the problem.

Here are some recommendations for control of Eastern Tent Caterpillar:

1. Search for and remove by hand any brown egg masses that have been deposited on branches. This can be done at any time from June through mid-March.
2. Remove and discard tents and caterpillars manually. The best time to do this is in the evening when caterpillars have migrated back from the leaves and branches into the webs.
3. Spray the foliage the biological control known ast "B.T." (Bacillus thuringiensis) in accordance with manufacturer instructions on the label.
4. More agressive chemical control should only be attempted as a last resort, and only after blooming is over. Remember that such chemical control works only on immature larvae that are exposed. Caterpillars are protected by the impermeable tents which would need to be torn open to allow contact chemicals to reach their target.