What is the spongy moth, and what is it doing to our forests?

Spongy moth caterpillars have destroyed trees throughout the Tri-state region.
Peter Steiner
Spongy moth caterpillars have destroyed trees throughout the Tri-state region.
MILLBROOK — One of the major factors in the cycle of the spongy moth and their proliferation — or lack of proliferation — turns out to be acorns.
Spongy moths, formerly referred to as Gypsy moths for their itinerant ways, were the topic of a lecture Thursday, Jan. 11, by scientists Clive Jones, who has studied the spongy moth for 30 years, and Charles Canham, who has studied northeastern forests for 40 years. Both are emeritus scientists of Cary Institute of Ecosystems Studies, which hosted the lecture.
Spongy moths, natives of Europe and Asia, came to North America in 1868 or 1869, to Medford, Massachusetts. Amateur entomologist Etienne Trouvelot believed he could crossbreed them with silkworms in an attempt to “make a hardy silkworm.”
“He got some egg masses of the spongy moth and set them on the sill of his open window. When they blew into his garden, he could not find them,” said Jones.
By 1891, there was mass defoliation in the Medford area and spongy moths were found in a 200-square-mile area. From there, they began to spread throughout the U.S. and Canada.
Alone, the spongy moth travels by ballooning on silk threads; assisted, humans unwittingly transport eggs laid on cut logs or vehicles.
The life of the spongy moth could be said to begin in July and August, when the flightless female moths emit pheromones to tell males that they’re ready to mate.
They each lay a few hundred eggs, often at the bases of trees. If the moth population is high, they lay eggs anywhere, on garden furniture or on the bumper of a car.
Then, the following May, the eggs hatch. The larvae spend May and June ballooning to new locations on silken threads. They rest under trees during the day, then go up into the tree canopy at night to feed. They prefer oaks but also eat maple, beech, apple, hickory, willow and birch trees, among others.
When the population is very dense and the competition for food is fiercer, they may eat all day and night. Once a tree is defoliated, they’ll move to the next canopy.
In late June and July, the larvae pupate — a caterpillar-to-moth metamorphosis that lasts a couple of weeks — then they emerge and breed and the cycle begins again.
Jones explained that “outbreaks” — or high densities of spongy moths — “occur about every 10 years on average, but like any average, it does not mean there will be outbreaks like clockwork.”
There are two major causes of outbreaks, he continued. One is “high female fecundity,” for example: If one moth laid 500 eggs and 250 were female, 125 of those would live to maturity and lay eggs. So, in year two, there would be 125 females laying eggs, and the third year, over 15,000 would result.
The other cause of outbreaks is the collapse of the white-footed mouse population, he said. White-footed mice eat the pupae as a part of their omnivorous diet.
At this point, we reach the subject of acorns:
“The number of mice is determined by the number of acorns the previous fall,” Jones continued, saying that if there is a moderate to large acorn crop in the fall, more mice survive the winter and begin breeding earlier in the year, in late winter or early spring. When that happens, there is an extra generation of mice, meaning more mice to eat more moth pupae.
Studies at the Cary Institute concluded that “moderate to high mouse densities keep moth populations low,” while it was found “that when the mouse population declines, the spongy moth population increases.”
However, defoliation of oaks can cause the trees to produce fewer acorns, meaning less food for the mice, meaning fewer mice the following spring, meaning more moths, and so on, until the moth population collapses again.
There are three major causes of population collapse among the moths.
One is a fungus, Entomophaga maimaiga, which kills the moth at moderate and high densities. It likes cool, wet springs and is more abundant in those conditions.
The more common cause of collapse is Nuclear Polyhedrosis Virus (NPV): When the moths are at high density, they are more stressed by the struggle to find food. Their immunity drops, they are more likely to catch the virus, and many are killed.
The third cause of moth population collapse is lack of food: When they defoliate a large area of trees and run out of food too early, they can’t mature and proceed to egg laying.
Jones said that Cary Institute scientists predict an NPV collapse in 2024: “Whether or not there’ll be a lot or a little defoliation [this year] will really depend on how fast the virus moves through the population. If it moves slowly, there’ll be complete defoliation. If it goes through fast, there’ll be incomplete defoliation.”
Canham continued the lecture by saying, “Defoliation by caterpillars is rarely a direct and immediate cause of tree mortality.”
Canham explained that this is due to “carbohydrate economy”: “Basically, photosynthesis during the growing season produces the sugars needed to produce new tissues, and the energy those tissues need for their metabolism.
“But the even more important outcome of a good growing season is the profit leftover after meeting those immediate needs, and that profit is in the form of sugars and starches that act as reserves for use next year.”
Usually, unless the tree is weakened by other factors, it will draw on its reserves to get through this defoliation and produce more leaves that same year.
An exception that Canham has observed at Cary Institute is the understory hemlocks, which don’t make as many reserves and, after a couple years of defoliation in a row, may not recover. Needle trees, DEEP has noted, can be killed if they lose more than 50% of their foliate.
Canham said he worries more about the devastating effects of the emerald ash borer, longhorn beetle, spotted lantern fly and hemlock wooly adelgid than about the spongy moth.
He said if a tree is in crisis, a way to help it is to water it to “help replenish its reserves.”
For more information or to view the lecture video, go to www.caryinstitute.org/news-insights/lecture-video/...
Built in 1820, 1168 Bangall Amenia Road sold for $875,000 on July 31 with the transfer recorded in August. It has a Millbrook post office and is located in the Webutuck school district.
STANFORD — The Town of Stanford with nine transfers in two months reached a median price in August of $573,000 for single family homes, still below Stanford’s all-time median high in August 2024 of $640,000.
At the beginning of October there is a large inventory of single-family homes listed for sale with only six of the 18 homes listed for below the median price of $573,000 and seven above $1 million.
July transfers
79 Ernest Road — 4 bedroom/2.5 bath home on 6.87 acres in 2 parcels sold to Matthew C. Marinetti for $1,225,000.
29 Drake Road — 3 bedroom/3.5 bath home on 2 acres sold to Harper Montgomery for $850,000.
6042 Route 82 — 4 bedroom/2 bath home on 1.09 acres sold to Spencer Thompson for $795,000.
125 Tick Tock Way — 3 bedroom/2.5 bath ranch on 1.9 acres sold to Fleur Touchard for $475,000.
August transfers
102 Prospect Hill Road — 3 bedroom/2 bath home on 6.35 acres sold to Karl Creighton Pfister for $565,000.
252 Ernest Road — 2 bedroom/1 bath cottage on .85 acres sold to Meg Bumie for $465,000.
1196 Bangall Amenia Road — 4 bedroom/2.5 bath home on 2.16 acres sold to Roderick Alleyne for $875,000.
Hunns Lake Road (#759929) — 59.1 acres of residential land sold to Argos Farm LLC for $3,325,000.
* Town of Stanford recorded real estate transfers from July 1 to August 31 provided by Dutchess County Real Property Office monthly transfer reports. Details on each property from Dutchess Parcel Access - properties with an # indicate location on Dutchess Parcel Access. Market data from One Key MLS and Infosparks .Compiled by Christine Bates, Real Estate Advisor with William Pitt Sotheby’s International Realty, Licensed in Connecticut and New York.
Hunt club members and friends gathered near Pugsley Hill at the historic Wethersfield Estate and Gardens in Amenia for the opening meet of the 2025-2026 Millbrook Hunt Club season on Saturday, Oct. 4. Foxhunters took off from Wethersfield’s hilltop gardens just after 8 a.m. for a hunting jaunt around Amenia’s countryside.
Joining in the fun at the dedication of the new pollinator pathway garden at The Millbrook Library on Saturday, Oct. 4, local expert gardener Maryanne Snow Pitts provides information about a planting to Lorraine Mirabella of Poughkeepsie.
MILLBROOK — Participating in a patchwork of libraries that have planted pollinator pathway gardens to attract insects and birds to their native plantings was one of the accomplishments being celebrated at the dedication of a new pollinator garden at the Millbrook Library on Saturday, Oct. 4.
“A lot of work went into it,” said Emma Sweeney, past President of the Millbrook Garden Club, who started the local library’s initiative two years ago.
The Pollinator Pathway program is a national effort to plant native plants that native insects depend upon for sustenance and preferred plants for their own seasonal reproduction.
Jana Hogan of Ridgefield, Connecticut, Executive Director of the Pollinator Pathway program, was on hand to present a plaque to the library for its successful participation.
“A garden is not just a garden,” said garden designer Andy Durbridge of Wassaic, designer of the library’s garden. “It may serve as a model for other gardens along the line.”
Speaking to the 50 visitors at the dedication, Durbridge said that the library’s garden has a mission, that it is a working garden, planned to serve insects and birds over their seasons. The earliest plants support pollinators, while the full range of plants continues to serve the needs of those they attract, offering habitat, shelter and food.
A pollinator garden is akin to a prairie, rather than a formalized European garden, Durbridge noted.
The garden project was supported by the library’s Friends group using funds raised during the Holiday Silent Auction and ongoing book sale. A grant from the Millbrook Garden Club also provided support.
Amenia Town Hall on Route 22.
AMENIA — After gathering comments from the Planning Board and the Zoning Board of Appeals, as it considers adding alternate members to those boards, the Town Board discussed possible changes to local laws governing those boards at its meeting on Friday, Oct. 3. The meeting date, usually on a Thursday, had been changed to accommodate a holiday.
In recent weeks Town Board attorney Ian Lindars has been compiling comments from the affected boards along with comments from the Town Board. The new laws may bring the appointment of two alternate members to each board. Alternate members are likely to be required to attend all meetings and be prepared to be seated if needed and be familiar with the applications being discussed. They would also need to take training required of all board members.
Lindars will prepare a draft of the new local laws to be reviewed by the Town Board and the affected boards.
As the Town Board begins work on the town’s annual budget negotiation process and anticipating an increase in some budget lines to accommodate major projects, the board unanimously approved three resolutions. The first will override the tax levy limit imposed on municipalities by the state of New York, a limit generally tied to the rate of inflation.
A public hearing on the proposal to override the levy limit was set for Thursday, November 6, beginning at 7 p.m. at the Town Hall.