Oaks & Gypsy Moths

Gypsy moths (Lymantria dispar) love oaks, and their caterpillars can strip a tree of its leaves in short order.

Some local governments spray to control the moths, typically using BT (Bacillus thuringiensis) applied while the caterpillars are still small - BT is not effective on caterpillars that are mature. There is a good summary of the pros and cons of BT available on the Ohio State University website.

Mature gypsy moths have a yellow-ish head, and distinct red and blue spots down their backs. In the photo, you can see one on a man's hand for scale.

They are similar in appearance to other caterpillars that you are likely to see in woods, such as the Eastern tent caterpillar and the Forest tent caterpillar.

The Eastern tent caterpillar makes silk tents, and favors cherry trees, apples and crabapples. These are native to the US, and while the tents may look bad, the insects rarely harm trees.

The Forest tent caterpillar has a blue head, blue sides to its body, and prominent yellow or white spots down the center of its back. This is a native species that favors aspens, sugar maple, oaks, birch & black gum trees.

Both of the native woodland caterpillars lay their eggs in a dark mass wrapped around twigs. The gypsy moths lay their eggs in a 1-3 inch long mass on the bark of the tree. The egg mass is tan, and covered with fine hairs.

If you see gypsy moth caterpillars, destroy them. If you notice egg masses on the bark of a tree, scrape them off into a container and either bury or burn them. Each egg mass contains from 100-1,000 eggs!

Here is a link to additional information on a Michigan State University website:
gypsy moth control & management.

IF YOU SEE A GYPSY MOTH IN ANYSTAGE OF LIFE CALL the Illinois Department of Agriculture TOLL FREE: 1-866-296-MOTH(6684)