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Gypsy Moth Caterpillar Explosion

e-gypsy moth caterpillars 273The Gypsy Moth was introduced into the United States in 1869 by a French scientist living in Massachusetts. Since then its range has expanded to include the entire Northeast south to North Carolina and as far west as Minnesota and Iowa.  The consequence of the introduction of this insect is staggering.  According to the U.S. Dept. of Agriculture, since 1980, the Gypsy Moth has defoliated close to a million or more forested acres each year. In 1981, a record 12.9 million acres were defoliated. This is an area larger than Rhode Island, Massachusetts, and Connecticut combined.

The Gypsy Moth females lay their eggs, usually on host tree trunks, in late summer.  The eggs overwinter and hatch in the spring.  Gypsy Moth caterpillars feed on a variety of species of shrubs and trees, with White Oak being their preferred host, metamorphose, mate and repeat this process.   Usually their numbers are not overwhelming, but due to the weather conditions we’ve been experiencing, the caterpillar population has skyrocketed in some areas, especially in southern New England.

Conditions were very dry in parts of New England in May 2014 and May 2015, which impeded the growth of a certain kind of Japanese fungus (Entomophaga maimaiga) that keeps the Gypsy Moth caterpillar population under control. Without this fungus present to keep their numbers in check, Gypsy Moths have flourished.   Although there was some rain this spring, there were many areas that did not get enough to benefit the fungus, and in these areas, trees are now stripped of their leaves.  It is possible in places in southern New England to track the pattern of rainfall simply by looking at where trees are still in full leaf.  Fortunately, the time has come for Gypsy Moth caterpillars to pupate, so most of this year’s destruction has already occurred.  Here’s hoping for a rainy May next year.

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13 responses

  1. Alice Pratt

    It’s definitely been extremely bad. Decks, driveways, sidewalks & streets coated with caterpillar poop & torn leaves. In your own yard & area, you can take a popsicle stick, old knife or screwdriver & a bag & go around & scrape the beige eggmasses from the trees & dispose of them. A friend cremated them in her fire pit. Make sure they are the “soft eggmasses” not the hard nest of an occassional Praying Mantis. Here on the South Shore, MA, trees right now have the white female moths on them laying egg masses.

    July 18, 2016 at 8:07 am

    • Thank you, Alice, for your valuable information about decreasing next year’s population by decimating egg masses!

      July 18, 2016 at 9:21 am

  2. I want to post a photo of an egg mass for gypsy moths so people can destroy it when they see one. But I think I will have to email it to you.

    July 18, 2016 at 9:28 am

  3. Wallie

    What is most interesting this year is that my yard is filled with the erratically flying male gypsies- to date I have seen no females flying and have found 6 females with egg piles (which I destroyed) and 3 or 4 egg batches on trees- I am on the lookout for the females and eggs

    July 18, 2016 at 10:01 am

    • Hi Wallie,
      Female gypsy moths have wings, but do not fly!

      July 18, 2016 at 1:06 pm

  4. Pat

    I tried to post these links in a reply on your Facebook page, but they kept getting deleted by Facebook. Last night I just happened to see this image of the devastation in RI as seen from space! I also read this article yesterday saying that NH has been largely spared this year:

    July 18, 2016 at 10:29 am

  5. Pingback: 20160715,16 Foggy morning, lots of bugs on milkweeds | Brtthome's Blog

  6. Wallie

    I had no idea the female gypsies didn’t fly! So they just ‘hatch’ in place and the males find them? Why are there so fewer females? Or does it only appear there aren’t as many because they aren’t flying about-I do know there aren’t as many in my yard this year as last (2015)-thankfully
    Guilford CT

    July 18, 2016 at 2:38 pm

  7. Jen Farquhar

    Several years ago my beautiful crab apple tree was being consumed by gypsy moth caterpillars. Day after day, I witnessed the rapid defoliation and, although I hate using pesticides, even their use wasn’t completely out of the question as I debated what to do. One day in frustration, I aimed a strong jet of water at every nest I could see high in the tree. I used a stick on the nests within reach. I really didn’t expect any changes. Later that day though, I noticed several chickadees, titmice and other birds picking the caterpillars out of the destroyed nests and happily swallowing them. I’m guessing that the birds can’t get through the moth’s webs with their bills but once the nests were opened they had no problem picking the caterpillars out of the strands. I’ve never had gypsy moth caterpillars on this tree since that summer.

    July 18, 2016 at 2:44 pm

  8. They are voracious!

    July 18, 2016 at 5:04 pm

  9. One detail not mentioned: when I arrived at my home town in Massachusetts this spring from Maine, I got out of the car and heard a curious sound – like it was raining. I went to investigate. I stood under trees and listened to the soft patter all around me, but I didn’t see anything. The sky was blue. What was that sound? Later I realized it was the excrement from the hundreds of caterpillars falling from the trees as they fed, landing all over the car, the house, everything. It felt like I was in a horror movie. On the day we left, I looked up and saw caterpillars crawling all over the house. I couldn’t wait to get out of there!

    July 19, 2016 at 9:39 am

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