They have not been seen yet in Wilton, but the Connecticut Agricultural Experiment Station (CAES) warned last week there has been widespread gypsy moth activity this summer in some areas of Connecticut.
Evidence of the destructive insect has been most notable in New Haven, Middlesex, and parts of Hartford and New London counties. Although Fairfield County is not on that list, sightings of gypsy moths in Easton have been reported to The Bulletin’s sister paper, The Easton Courier, and one gardener reports seeing them along the Merritt Parkway.
Their emergence has been associated with a very dry spring this year, which prevented early control by the gypsy moth fungus Entomophaga maimagia. Moisture is required for the fungus to infect the gypsy moth larvae (caterpillars). With current rains, however, caterpillars are dying from the fungus.
“It is likely that this pathogen will knock back the gypsy moth population and help prevent a possible large outbreak in 2016,” said state entomologist Dr. Kirby Stafford. The impact of the fungus on any gypsy moths in 2016 will be dependent on weather conditions in May and early June of next year.
The gypsy moth was first detected in Connecticut in Stonington in 1905. The high level gypsy moth activity this year shouldn’t mark a return to multiple years of widespread gypsy moth defoliation and the tree mortality experienced in the early 1980s. In 1981, 1.5 million acres were defoliated in Connecticut.
Trees that lose their leaves this year are not necessarily doomed. Christopher Martin, director of forestry at the Connecticut Department of Energy and Environmental Protection, said that in general, “partial or even complete defoliation of a tree in any one year does not mean the death of the tree. Healthy trees can tolerate some defoliation.”
The last outbreak of gypsy moth activity in Connecticut was in 2005 and 2006. In 2005, gypsy moth caterpillars caused 64,273 acres of defoliation, mainly in Middlesex County. A more widespread outbreak in 2006 caused 251,946 acres of defoliation, largely in Middlesex, New Haven, and New London counties. It was eventually brought under control by the fungus and the arrival of early summer rains; a pattern similar to this year.
There is only one generation of the gypsy moth each year. Caterpillars hatch from the buff-colored egg masses in late April or early May. An egg mass may contain 100 to more than 1,000 eggs laid in several layers. A few days after hatching, the inch-long caterpillars will ascend the tree and begin to feed on new leaves. These young caterpillars deposit silk trails as they crawl and, as they drop from branches on these threads, may be distributed on the wind. Larger caterpillars generally crawl up and down tree trunks and feed mainly at night. However, under outbreak conditions with dense populations, they may feed continuously day and night.  The caterpillars generally complete their feeding sometime around the end of June and the first of July and seek a protected place to pupate and transform into an adult moth in about 10 to 14 days. The female moths, which are white and cannot fly, will lay a single egg mass and die. These eggs will pass through the winter and larvae will hatch the following late April or early May.
One population control measure is to remove and destroy egg masses, if any, found on tree trunks, decks, vehicles, outdoor furniture and other locations before the larvae hatch next spring.