Getting Rid of Tent Caterpillars

Question:

My crab apple tree has caterpillars in silk bags in the crotches of limbs. How do I rid the tree of these and prevent further issues?

Note: I sprayed Sevin on the trunk from the base to 2 ft high on 17 March, on 19 Mar I noticed the first silk bags forming. Most of the silk bags are 12-25 ft high.

Hardiness Zone: 7a

Scott from Hollywood, MD

Answer:

Scott,

Eastern Tent caterpillar larvae feed on the leaves of most deciduous trees and shrubs, but especially crab apples, aspens and wild cherry trees. In the past few years, caterpillar numbers have been high in your area. Thankfully, these population explosions are cyclical, and native parasites will eventually bring numbers back under control.

One idea for getting rid of the sacks high up in your tree is to wind them onto a broomstick with nails projecting from it. This is best done in the morning when the caterpillars are inside their tents. Where you can reach, you can also prune and burn the infested branches. Another, (microbial) method of control is spraying Bacillus thuringiensis var.kurstaki, also known as (BTK).

This is a bacterial insecticide that caterpillars ingest as they feed. It poisons them over the course of a few days and they drop to the ground. BTK should be applied while caterpillar larvae are still small and easy to control. It is applied in the evening or early morning when the caterpillars are in the nests.

One way to prevent future infestations is by attracting native parasitic flies and wasps. This can be done by growing small, flowering herbs like Queen Anne's lace, catnip, and wildflowers around your garden and near the base of your tree.

Here's a great link for more information specific to your area.

Good luck!

Ellen