Dans Papers - June 8, 2007 - Traveling Gypsies

My phone rang at 7 a.m. this morning. I heard my daughter Michele's voice, high-pitched and in great despair.

"Mom, I'm moving out of Sag Harbor," she said.

"What," I said, "Why?"

"These Gypsy moths are driving me crazy. I can't stand it anymore. Anthony had them crawling all over his shirt when he came home from school today. One bit him. He has a rash. It's horrible!"

After I reminded her about the infestation we had fifteen years or so ago, leaving practically every tree and bush stripped of their beautiful leaves and the landscapes practically baron, she calmed down. "There is nothing you can do about this creature. They arrive, they destroy and then they leave," I told her.

The gypsy moth (Lymantria dispar) is of Eurasian origin. Originally ranging from Europe to Asia, it was introduced to North America in the late 1860s and has been expanding its range ever since. Like the tale of the sorcerer's apprentice, the gypsy moth is an example of an experiment gone horribly wrong. The moth was brought to the United States in 1869 in a failed attempt to start a silkworm industry. Escaping soon after, the gypsy moth has become, over the past century, a major pest in the northeastern United States and southeastern Canada. There is only one generation per year.

Gypsy moth egg masses are typically laid on branches and trunks of trees, but egg masses may be found in any sheltered location. Egg masses contain from a couple of hundred to about 1,200 eggs. Tree damage is caused by the insect larvae, or caterpillars, which emerge from their eggs beginning in early spring and continuing through mid-May. The larvae move to the leaves of trees and begin to eat, mostly at night. You can actually hear them chewing the leaves in the evening.

Gypsy moth larvae grow by molting - five molts for males and six for females. Feeding occurs during the "instar" stage between each molt. As might be expected, a caterpillar's appetite increases with each molt. Feeding continues until mid-June or early July when the caterpillar enters the pupal stage emerging, finally, as a moth. After the females lay their eggs from July to September, depending on location, moths of both sexes die.

The gypsy moth caterpillar is not a fussy eater. It has a preference for the leaves of deciduous hardwood trees such as maple, elm and particularly oak. Gypsy moths can also feed on apple, alder, birch, poplar and willow trees. As it grows it will also attack evergreens like pines and spruces. They appear to dislike ashes, sycamores, butternuts, black walnuts, dogwoods and balsams. However, during heavy infestations, competition for food will drive the caterpillar to attack almost any tree or shrub. Most deciduous trees can survive a moderate degree of defoliation. Egg masses appear as 1.5 inch, tan or buff-colored hairs on tree trunks, outdoor furniture or the side buildings.

Gypsy moth caterpillars change appearance as they grow. Young caterpillars are black or brown and about 1/4 inch in length. As they grow, bumps develop along their backs along with coarse, black hairs. Mature caterpillars can be as long as 2.5 inches.

Gypsy moths are seen only in mid-summer. Males are grayish brown and can fly. Females are larger, whitish with black marks and cannot fly. The Gypsy moth can be combated at the egg and larval stages. Egg masses, when discovered, should be burned or soaked in water or kerosene. The caterpillars will crawl underneath the burlap seeking shade. I usually store the ashes from my fireplace in a large garbage bag and in early spring I spread them around the trees closest to my house. It seems to discourage the gypsy to climb the tree.

There are a variety of commercially available pesticides for use in dealing with heavy gypsy moth infestations. Consult your local tree care specialist for information and advice on the use of any these products.