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A Gypsy Moth Invasion

If you grew up in the ‘80s, you may remember the widespread panic and carnage caused by the feared gypsy moth outbreak. Several trees still bear the scars of the insatiable hunger of these tiny caterpillars. Twisting in the wind, hanging down from invisible silk safety line suspensions, these insects, whose Latin name is Lymantria dispar, are back.

“It seems to be a subject on the tips of everyone’s tongues right now,” said Chester First Selectman Lauren Gister, who is getting an earful about the insects on a daily basis.

“From what I understand it should all be over soon,” said Gister.

According to the Chester Conservation Commission, the last time gypsy moths were a big problem in state, a disease caused mass die offs and that solved the problem for almost 30 years.

Dr. Kirby Stafford III, head of the Department of Entomology at the Connecticut Agricultural Experiment Station (CAES), has written a fact sheet about the destructive insect. The guide explains the caterpillar was first introduced into the United States via Massachusetts circa 1860. The escaped larvae led to small outbreaks in the area in 1882. They were first detected in Connecticut in 1905. By 1952, outbreaks had spread to all 169 towns in the state. In 1981, 1.5 million acres were defoliated in Connecticut. During the outbreak of 1989, CAES scientists discovered that an entomopathogenic fungus, Entomophaga maimaiga, was killing the caterpillars. Since then, the fungus has been the most important agent suppressing gypsy moth activity.

According to Essex Tree Warden Augie Pampel, the potential for gypsy moth outbreak exists every year in our community. For this reason, he is encouraging residents to keep an eye out for the pesky caterpillars, which can defoliate trees, and detrimentally impact trees’ ability to prosper and thrive.

The caterpillar feeds on a wide range of trees and shrubs, its favorite being oak trees. However it will also consume apple trees, birch, poplar, and willow. The feeding causes extensive defoliation. According to Stafford, healthy trees can generally withstand one or two partial or one complete defoliation, but there may be die-back of branches.

Older trees may become more vulnerable to stress after defoliation, weakening them to attacks by other organisms, or lack energy reserves for winter dormancy and growth during the following spring. Three years of heavy defoliation may result in high oak mortality.

Stafford explained that in 2005-’6 and again in 2015, there were reported hotspots for the moths in the state. This year, it seems as though some of those hotpsot areas have been noticed in the tri-town areas of Chester, Deep River, and Essex with Mystic and Stonington also reporting high densities of the insect according to Pampel.

Stafford explained the life cycle of the gypsy moth is one generation a year. Caterpillars hatch from egg masses in late April to early May. An egg mass may contain 100 to more than 1,000 eggs and are laid in several layers. The caterpillars (larvae) hatch a few days later and ascend the host trees to feed on new leaves. The young caterpillars lay down silk safety lines and drop from branches on these threads, at which point they may be picked up on the wind and spread.

There are four or five larval stages (instars) each lasting 4 to 10 days. The fourth instar caterpillars, with distinctive double rows of blue and red spots, crawl up and down the tree trunks feeding mainly at night. They seek cool, shaded protective sites during the day, often on the ground.

If you are in a high density gypsy moth area, brace yourself for June and early July, which is when feeding will be complete and the caterpillars will seek protected spots to pupate and get ready for their transformation into a moth. This takes anywhere from 10 to 14 days. After mating, the female will lay a single egg mass and die. The eggs will survive the winter and larvae hatch the following spring during late April through early May.

According to the Chester Conservation Commission, two actions can help in the short term: burlap hiding places can be put around hard wood tree trunks to catch the caterpillars before they climb up. These should be de-caterpillared daily. This, however, is only marginally effective. The second, after the egg cases (tan fuzzy blobs) are laid, they can be scraped off tree trunks and where ever else they can be found and destroyed. This will reduce next year’s population.

For complete information about the gypsy moth and its management, visit the CAES website www.ct.gov/caes and look for the fact sheet on gypsy moth. You may also email Augie Pampel at augiepampel@att.net with questions and concerns.