Florida Farm & Feed

The Eastern Tent Caterpillar

Facts about Cherry Trees and Tent Caterpillars
Caterpillars of Eastern Forests

The eastern tent caterpillar is often mistaken for the gypsy moth. Though they are similar in appearance, they differ in habits.

The fully grown eastern tent caterpillar is about 2 inches long, black with a white stripe along the middle of the back and a row of pale blue oval spots on each side. It is sparsely covered with fine light brown hairs.

The gypsy moth caterpillar, when fully grown, is also about 2 inches long, but it has pairs of blue and red spots on its back. Compare the photos below to see the difference.

Tent caterpillars spend the winter in egg masses that are in shiny brown bands around twigs (Figure 4).

The gregarious caterpillars hatch in the early spring about the time tree buds start to open, and soon they begin to spin their silken tents in the branch forks (Figure 5). The tent protects them from predators, such as birds, and from temperature extremes. Enlarging the tent as they grow, the caterpillars leave only to feed, usually at night.

The eastern tent caterpillar is found most often on apple and wild or ornamental cherry, and occasionally on pecan, hawthorne, beech and willow. When abundant, caterpillars will eat all the leaves, weakening, though seldom killing a tree.

Leaf-feeding can be prevented on small trees by destroying tents with a stick or pole, exposing the caterpillars to birds. Another preventive method is to prune the egg masses from twigs before the early spring hatch.

"This was an excellent year for caterpillars," said Fitzgerald, who has studied the Eastern tent caterpillar since 1976. "Next year should be a very big year, too, where I am located (New York). Then another year there should be a lot, then the numbers will crash because of a bacteria or virus or weather."

When asked if he believed the caterpillar could cause the extreme problems seen in Kentucky and other states this spring, Fitzgerald said, " Cyanide has that potential, and the caterpillars have cyanide in them (from eating black cherry tree leaves). And if it got into the horse it could harm the horse. There are a lot of unknowns in the Kentucky situation. The pathway is not known, and there is no precedent in literature."

"We think there is an association with cherry trees and tent caterpillars and the problems we've seen, based on examinations of pastures of farms badly affected," said Dr. David Powell of the Gluck Equine Research Center and one of the leaders in the research team. "We have noticed an association with the presence of cherry trees (the favored meal of tent caterpillars) in pastures where mares lost fetuses, and the presence of massive numbers of caterpillars."

"The Eastern tent caterpillar is not only unaffected by cyanide, but one study suggest that the caterpillar may actually use the compound to its advantage. Eastern tent caterpillar larvae common regurgitate defensively when attacked by predators or parasitoids. Regurgitated juices collected from caterpillars that have just eaten contain both benzaldehyde and cyanide at the same concentration in which they occur in the leaves. It has been suggested that the Eastern tent caterpillar may arm itself intentionally by feeding preferentially on the youngest host leaves, which have the highest benzaldehyde potential."

For now, testing will continue to see if cyanide or some product broken down from cyanide can be found in equine samples. ¶