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Caterpillar Deforestation Throughout New England


Nasty caterpillar invasion Spring 2022

My family and I went for a nature hike on a public trail in Alford, Massachusetts yesterday, a beautiful June day in 2022. Not long after we climbed the initial slope and got into the forest I discovered that the caterpillars were back, in droves! All along the hiking trail we saw evidence of sliced and diced green tree leaves scattered all over the forest floor. In fact, we could hear the caterpillars' feces dropping like rain on last year's dried leaves, as well as feeling them drop on us! Gross! I knew that we've had some pretty bad infestations in recent years which prompted me to do a bit of research after we came back home.

Neighboring states also under attack

Residents, arborists, and foresters in Litchfield County, Connecticut have also reported large amounts of spongy moth egg masses. In March 2022, Dr. Victoria Smith, CAES Deputy State Entomologist was quoted:

"Our 2021 state-wide gypsy moth egg mass survey, especially in northwestern Connecticut, showed large amounts of spongy moth egg masses, which leads us to believe there will be a continued hatch and extensive caterpillar activity in 2022"


A century-old problem

According to the Current Forest Health Threats at the Lymantria dispar has been a costly and persistent problem in Massachusetts for over 130 years:

"The first major defoliation in event in Massachusetts occurred in 1889. It is at this point Massachusetts state agencies became involved and began efforts to control this pest. Lymantria dispar management began as a labor intensive process, including removing egg mass and applying treatments by hand. As technology advanced, the use of spray trucks and eventually aerial pesticide applications (including the use of DDT) were used. Despite continued efforts of control, they spread to every city and town in Massachusetts by 1922 and has remained a major threat to forest health in the state."

I also discovered that Entomological Society of America adopted the name "Spongy Moth" for Lymantria dispar due to the previous name, "gypsy moth," being a derogatory term for the Romani people.

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The recent four-year caterpillar bug-fest

I remembered that the spring of 2016 was the beginning of a four-year onslaught of these invaders, peaking in 2017 throughout most of Massachusetts. In fact, I can recall that in 2019 I had an in-home appointment with a client who resided on Blue Hill Road in Great Barrington. As I started to drive up the hill I saw the same evidence that I witnessed yesterday, an endless number of shredded green leaves all over the road as if a tornado or wood chipper had diced and tossed the leaves everywhere. In fact, at the client's home (which was surrounded by forest) my vehicle was pummeled by so much caterpillar poop that it literally sounded like sleet falling on my vehicle in his driveway! Nasty!

Is there anything that can stop these pests?

Apparently wet spring conditions can activate a naturally occurring soil borne fungus called Entomophaga maimaiga which is lethal to only spongy moth caterpillars and normally keeps their populations in check. However, cyclical outbreaks result in widespread tree mortality after several dry springs and corresponding consecutive years of defoliation. Wet spring weather eventually returns favoring growth and effectiveness of the fungus which ends these caterpillar infestations. New England states have opted to allow nature to take its course, letting the fungus do the job of insect control instead of mass-broadcasting pesticides and other dangerous chemicals.

How to get rid of spongy moths naturally

Lymantria dispar can totally defoliate trees, shrubs, and plants in your yard during an epidemic, but here are a few natural and eco-friendly ways to get rid of these pests...

  • Scrape off spongy moth egg masses, they are tan and hairy. As a result, wear gloves when scraping the hairs off the fuzzy eggs. Also, don't scrape egg masses on the ground, where they might survive. Rather, soak them for two days in a bucket filled with soapy water. After that, discard them. To protect the tree from injury, use a paint scraper or knife to scrape them off.
  • Make a bucket of dish soap and water once you've found these hairy, dark-colored caterpillars with blue and red patches on the back. Put on some gardening gloves and go around collecting caterpillars and egg masses from trees. Toss them in the soapy water, eggs and all. They will be suffocated and killed by the solution. A DIY spongy moth caterpillar spray may also be made by mixing 5 tablespoons dish soap with a gallon of water. Spray the creatures and sensitive trees including oak, birch, pine, willows, elm, and maples.
  • Remove any dead branches from your yard and clean it up. Limbs should also be trimmed, and tree stumps should be cut back. Adult female moths deposit their eggs in detritus like this, so keeping your yard tidy will help you avoid an infestation. The eggs are placed in large groups, sometimes including hundreds of eggs. During the cleanup, you may see them.
  • Woodpiles that are generally used as fuel in the winter are appealing places for female spongy moths to lay egg masses in the summer and fall. As a result, covering woodpiles with tarpaulin will keep these pests at bay.
  • Birds are a natural spongy moth control strategy, and while dining on seeds, they will eat any larvae detected. As a result, attracting birds to the garden can be as simple as growing attractive plants like sunflowers. In addition, place a bird feeder on the grass or in the yard. Orioles, black-billed cuckoos, blue jays, and chickadees will flock to the area to feast on unwelcome moth larvae. A water fountain will also aid the birds' arrival at the feast.
  • Trichogramma wasps are microscopic parasitic wasps that feed on the eggs of moths. They put their eggs inside the bugs' eggs. The larva of the Trichogramma egg feeds on the host egg and kills it when it hatches. Trichogramma minutum can be purchased from a variety of sources and released according to the packaging directions. Furthermore, cutworms, borers, and armyworms are all controlled by these parasitic wasps.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Arthur Dellea

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