Early May rain needed to prevent another severe gypsy moth infestation
Though Friday’s snowfall and the additional snow expected next week is keeping them buried for now, the buff-colored egg masses of gypsy moths clinging to trees, stone walls, fence posts and other surfaces soon will be stirring to life with the coming of spring later this month.
“There are a lot of egg masses out there,” Kirby Stafford, state entomologist with the Connecticut Agricultural Experiment Station, said this week. “We’re going to see a lot of gypsy moth caterpillars hatching around the third week of April.”
Last year’s infestation, concentrated in Middlesex, New London and Windham counties, defoliated 204,176 acres, according to experiment station maps, up from the 180,000 acres defoliated in the 2015 outbreak. Unless rains come at the right time to activate a fungus that kills the gypsy moth caterpillars that strip trees bare of leaves, 2017 could be a third consecutive heavy year for the invasive insects, and the breaking point for many trees. While white oaks are especially preferred by gypsy moths, sugar maple, beech and birch trees also are favored.
“We need rains in early May to get the fungus going,” Stafford said.
Drought conditions in 2015 and 2016 suppressed the fungus and added to the stresses on trees, and while the state is still officially in a drought, precipitation over the past few months has been getting closer to normal levels, he added.
“It’s hard to predict what’s going to happen this year,” Stafford said.
While the defoliation was intense in some areas of the state, including local forests near the Connecticut River and the Rhode Island border, it was “patchy” overall, Stafford said, with the western and north-central parts of the state untouched. The amount of denuded forest over the last two years, he noted, is nowhere near the scale of outbreaks in the 1970s and 1980s, when up to 1.4 million acres statewide were defoliated in one year.
The invasive pest, originally from Europe and Asia, accidentally was introduced into this country in the late 1800s. It was first found in Connecticut in Stonington in 1905, and had spread statewide by 1952.
“We did some spraying in the 1980s, but the state isn’t going to take any direct action now,” Stafford said. “It’s a resource issue. It costs $50 to $60 per acre at least to do aerial spraying, and it’s very controversial.”
Chris Martin, forestry director for the state Department of Energy and Environmental Protection, said large sections of the Pachaug State Forest in Voluntown, Griswold and North Stonington, which had an intense infestation in 2015 and 2016, will be monitored closely. Last year, the state decided to log a 256-acre stand in the Pachaug to rid the area of dead and dying trees deemed a safety hazard to nearby roads and hiking trails. More trees could succumb this year, he said.
“Trees can survive two years of defoliation, but after the third year they could succumb completely, especially if they weren’t healthy to begin with,” Martin said.
He advised homeowners concerned about specific trees on their property to contact an arborist now to evaluate whether they should be sprayed with Bacillus thuringiensis, or Bt, a biological insecticide. Trees should be sprayed just after the leaf buds open in early spring, he added.
John Simons, who lives near the Pachaug State Forest in Voluntown, is concerned that another year of defoliation is ahead, and has been urging Stafford and DEEP officials to undertake spraying. The state entomologist, he believes, is obligated to take the action in cooperation with affected towns by state statutes enacted after outbreaks in the 1970s.
“Southeastern Connecticut will be defoliated even if we get the fungus, because there are so many egg masses,” Simon said. “We have a couple of months before a calamity.”
Martin and Stafford, however, said that while they sympathize with residents like Simon who live in areas hard hit by the gypsy moths, the outbreak is not severe enough to warrant spraying.
Forests owned by Avalonia Land Conservancy in six local towns were among areas that experienced defoliation the last two summers. The Greenman Preserve in Ledyard saw some of the most severe damage, said Karen Askins, chairwoman of stewardship for Avalonia. A town committee in Ledyard has been studying possible responses to the infestation for months, and while an association of homeowners who live near the preserve are planning to spray their neighborhood, Avalonia has decided not to participate on its land, she said, because the Bt insecticide kills butterflies and other moths’ larvae along with the gypsy moth caterpillars.
“We may have a lot of dead trees as a result,” she said. “I’m just hoping for a wet spring.”
A tree die-off, she added, is not necessarily a bad thing, because it can open up a forest for a different kind of habitat.
“The death of trees is a natural process,” she said.
The Lyme Land Conservation Trust, which had “patchy” defoliation on several of its properties, is taking a similar view of the situation, said Anthony Irving, preservation chairman for the land trust.
“I am finding more egg masses this year than last year,” he said. “The trees that may die have been getting the most stress, and that will open up growing space for those that survive.”
While the land trust isn’t planning any action to combat the gypsy moths, Irving did offer advice to homeowners who may want to spray or erect physical barriers on individual trees on their own property. His advice was included in the organization’s winter newsletter.
For more information
- To read Anthony Irving's article in the Lyme Land Conservation Trust's Winter 2017 newsletter about how to minimize defoliation of gypsy moths, visit http://bit.ly/2mKUOTM.
- Connecticut Agricultural Experiment Station maps of gypsy moth defoliation and a fact sheet can be found at http://bit.ly/2mabHDc.
Connecticut defoliation caused by gypsy moth in 2016
Data source: Connecticut Agricultural Experiment Station
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