Scouting for Pests in Winter

Winter is the perfect time to scout for several of the most devastating pests of eastern trees...

The Eastern tent caterpillar and Gypsy Moth cause early spring defoliation of our trees. Scouting and destroying their egg masses in fall and winter can greatly reduce populations in the home landscape.

Eastern Tent Caterpillar masses contain 150-350 eggs in each mass. The egg mass of this species encircles small twigs about pencil size in diameter, and appears dark (almost black) and varnished. Hatching begins about the time cherry trees leaf out. There is only one generation a year in Pennsylvania. The preferred hosts are, but are not limited to, cherry, crabapple and apple. When masses are found in the winter, the twig can be pruned out and the mass destroyed (do not leave on the ground to hatch in the spring).

Gypsy moth egg masses are buff to cream colored and are laid on branches and trunks of trees, but egg masses may be found in any sheltered location. The egg mass may contain 400-600 eggs per mass. The preferred host for the caterpillar is oak, but egg masses may be found on birch, aspen, alder, sweetgum, and hawthorn. The egg masses can easily be scraped off the tree, but don’t simply leave them on the ground because they may still hatch. Scrape them into a pail of soapy water and allow the masses to soak through before disposing of them in the trash. If they are scraped onto the ground, crush the mass with the heel of your boot. Caution is urged if touching the egg mass with bare hands. The hairs that coat the egg mass can cause an allergic reaction for some people.

One other pest easily spotted in the winter is bagworm. What may look like an odd pinecone is actually the protective nest of the female parent and is filled with 500-1000 eggs waiting to hatch in the spring.

These bags may be seen on arborvitae, juniper, pine, spruce and many other evergreen species. However, they may also be found on trees like black locust, honeylocust, and sycamore. When spotted, the easiest way to remove them is to handpick or cut the bags from infested trees and destroy.

For more information about these, visit the insect pests and other landscape and forest pests website or contact your local Penn State Extension Office.

By Sharon Telesky, Penn State Master Gardener