On my father’s land in Franklin the June skyline looks like late fall.
In the woods of Mattapoisett Neck and doubtless other arboreal forests of the SouthCoast, the ugly truth is revealed like a scene from a B- horror movie. An apt name might be: “Invasion of the Leaf Snatchers” or “Creepy Crawley Show” or simply “Mothra II.”
It’s enough to make any mortal cower and shiver. And it’s keeping the local tree warden awake at night.
Chomp! chomp! chomp!
The next stage (pupation) will render these hairy, warty gypsy moth caterpillars into moths that will lay eggs, perpetuating the cycle of destruction for next year.
As with everything, there is good and bad news. First the good ... The rampant rains of spring have cooked up a perfect storm of deadly fungal disease known as entomophaga maimaiga and that is the death knoll for many gypsy moth caterpillars. They become gooey, droopy, brown, liquid-filled cadavers and as I did walk the woods the other day that seemed to be the case. Yet I wondered how they managed to still cling to the tree trunks, begging the question were they dead or only mostly dead?
David Mendell, a certified arborist with Seekonk-based Bartlett Tree Experts told me looks can be deceiving.
“What you’re seeing is caterpillars coming out of the leaves descending from the trees which is a natural instinct then resting in a a sort of weird pupation stage. Next week they will emerge as moths. They will mate and lay eggs primarily on the trunks of trees.”
Mendell is coming to the end of his most intense gypsy moth watch.
“I live with the caterpillars for two months (usually May and June) of my life each year,” he said.
By then he can anticipate whether it’s going to be a problem. Gypsy moth caterpillars favor oak (which is what they feasted on at my parent’s property) but, Mendell says they’ll feed on cherry, beech, birch and maple, and when years are really bad, white pine and spruce.
“Last year we saw that, but not too much this year in Southeastern Massachusetts,” he noted, adding that Little Compton and Marion had a significant problem but not as widespread as it could have been. Same goes for properties he visited in Westport and Dartmouth.
Birds can help with control, though he says it’s hard for them to keep up. They also have difficulty with digesting the hairy aspect of these pests. Applying sticky tape around tree trunk to potentially capture capture hatched caterpillars is another small way people can exert control, although it’s mostly effective when dealing with a lone tree. A lot of eggs are laid above the tape and caterpillars once they hatch and are in the canopy they hang by a thread and are blown from tree to tree “ballooning” like weightless tiny skydivers, noted Mendell.
On a sunny day in May you’ll see them, and as goes with the territory, Mendell admits they haunt him, whether he’s on the job or not. He laughed about how he was recently attending a graduation ceremony where he happened to look up and see their thread trajectories across his line of view.
As for the bad news: Mendell says if the same tree is defoliated two to three years in a row it can kill the tree.
“If a tree is leafless in August, that is a good indication it will die. But some that experienced a defoliation may have a second leafing out," he said. "If people have special trees, the best thing to do is to water and fertilize, which can save money over future removal.
“Last year’s drought coupled with the caterpillar problem has been a one-two punch for a lot of trees. Many are on the fence, but there are proactive steps you can take to help the trees.” It is important to “not string them along as they can get brittle and break.” So best to get an arborist he advised.
Mendell works closely with tree wardens in Southeastern Mass and “we don’t want to have to spray if not needed.” He said that Bartlett uses products that are safe to environment, the client and the worker applying it as well as bees but that it is much pricier than many of the more toxic chemicals out there.
Roland Cote, Mattapoisett Tree Warden, who has been grappling with the gypsy moth infestation, works closely with Mendell and the mutual decision was not to spray this year since the cycle is practically over and not many trees in the village or on scenic roads were hit.
He observed some trees that were “beat up” outside the village.
“About a week ago I was driving down Brandt Island Road and there were several trees exfoliated. They didn’t even make their first leaves," he said. "I’m waiting to see if the second set comes out.”
Cote admits that it’s easier to save the lone specimen trees and almost impossible to deal with massive infestation. “You can’t go up against the forest.”
In September he said they will feed trees that need it. Cote, in conjunction with the town’s Tree Committee, has planted more then 60 trees over the past decade.
While the reports of caterpillar dieback bodes well, the eastern part of the state has been unduly weakened by a variety of insects. Dr. Joseph Elkinton a professor in the UMass Amherst Department of Environmental Conservation has been closely following the outbreak and mapping areas all over the state. In a report in Mass Wildlife Magazine (No3, 2016 issue) he co-wrote with Jeff Boettner Elkinton documents in laymen’s terms and explains the ecosystem perspective.
“In eastern Massachusetts, some trees had already been defoliated in May by the winter moth, Operophtera brumata, another invasive defoliator from Europe. They were then defoliated a second time by gypsy moth after they had already started putting out new leaves. On Cape Cod, there is yet another oak-feeding insect in outbreak conditions, the black oak gall wasp, Zapatella davisae. We are worried that stresses from all the sources may cause a lot of oak mortality this year in Massachusetts,” writes Elkinton.
Last year’s outbreak (the worst in 35 years), encouraged by the drought, caused 350,000 acres of defoliation throughout Massachusetts according to the Massachusetts Department of Conservation and recreation.
The gypsy moth has a natural range that includes most of Europe and Asia. It was introduced into North America in 1868 or 1869 by Leopold Trouvelot who hoped to use this moth species as the foundation of a silk industry in the United States, according to a Pennsylvania State University report. The cocoon threads of the gypsy moth did not prove to be a reliable source of silk, but the moths were able to escape Trouvelot’s Boston home-laboratory and were also able to survive and then thrive in the hardwood forest ecosystems of Massachusetts.
That environmental impact is a subtle chain reaction of events, excerpted here from the Penn State report. Obviously, trees that are partially or completely defoliated are energetically stressed as they miss days of photosynthesis and have to spend energy reserves generating replacement leaves. These trees will be more susceptible to disease and environmental stresses like drought and will have reduced rates of growth.
Most healthy trees, though, survive these defoliation events as long as they are not too severe or are not repeated over too many successive years. Second growth leaves are typically tougher and thus more resistant to leaf predators like the gypsy moth. These second growth leaves, though, are also more resistant to decomposition. Nutrient cycling, then, in both the forests and leaf-fed streams around the forests can be disrupted by these reverberative impacts of the gypsy moth larvae.
Some have expressed the view that gypsy moth predation on trees is a positive force that selects for stronger, healthier trees. The preference of the larvae for oak species, though, makes the nature of this overall impact less obvious. The stimulation of the growth of forest under-story vegetation by the thinning of the leaf canopy is also a consequence of gypsy moth activity. What the long-term impacts of this altered and accelerated pattern of forest succession will be is not known.
QUOTE: “I can feel it coming in the air tonight, oh Lord...” Phil Collins