Invasive, Destructive & Downright Yucky. How Do We Kill Gypsy Moth Caterpillars Without BT?

The mornings are especially magical this time of year, as there is still a sharp and sparkly frost on the ground, but new life is rising and persisting, despite the cold. After throwing on a big sweater and a hat, I usually put on my wellies and thump through our heavy wooden door with my dog, Lupin around 6:00 AM. While she sniffs in excited zigzags and finds trails of scent left by the previous night’s visitors, I will sip my steaming coffee and take note of my gardens and the perimeter of the property.


So far, I have counted a dozen tulips and lilies poking up and a few dozen daffodils and snow drops. I was laughing to myself this morning because the majority of the daffodils are spread randomly throughout the wood line and are clearly the result of some sneaky squirrel dragging away a tasty snack and leaving the rest behind. They like to do this with my beets too.


Although we have been living here for nearly a full year, we are still learning many new things about our land and the critters who share it with us. We know we have deer and we know we have rabbits (affectionately referred to as bun-buns here), but we have been continually and pleasantly surprised by the number of song birds, owls, falcons and hawks we have seen and heard. To every good there is a bad, however, and the balance to our abundance of joyous wildlife is a nasty one. The non-native and absolutely unpleasant critter I am referring to is the gypsy moth caterpillar.

Gypsy Moth Eggs On White Pine Tree On Our Property

I  generally believe that everything serves a unique and necessary purpose, but the purpose of the gypsy moth is still lost on me. We first became acquainted with the gypsy moth caterpillars in their tiniest larva state. They were mini brown worms, no bigger than a few millimeters and they were crawling on our Adirondack chairs. We foolishly brushed them away, thinking little of them. It wasn’t until I developed an itchy rash on my arms that I looked into what they were.

A few weeks later, the worms had grown into inch-long, hairy beasts and they were everywhere – covering our home, our porch, our lawn, our gardens and our trees. We had strings hanging from our eaves and every morning we were bombarded by them as they repelled down from the branches of our once strong and majestic white oak trees. Each time the wind blew, pieces of eaten leaves would come fluttering down into piles. When we sat on our screen porch, we could hear worm pellets hitting the roof and the ground. We joked that it might be free fertilizer, and then looked down and realized they were bouncing off of the outside hanging planters, through the screens and into our drinking glasses. It was at that point that we decided we needed a plan of attack. Nobody messes with my husband’s tasty craft beer.

A Little History & Issues…

They don’t have many known natural predators in North America. My neighbor said that mice might eat them, but the larvae significantly outnumber the mice around these parts. Other known predators are fungal and viral in nature, but those need moist conditions to thrive. Our area was in a drought for a prolonged period, so there was no help from these fellows last spring.

They defoliate our trees and make them sick, which causes them to drop branches and fall down. My husband and I are pretty convinced that the reason so many trees fell on power lines this past autumn and winter is because many of the large white oak and hemlock trees in this part of the state are so weak from the past few years of playing host to the larvae of the gypsy moth. When the winter winds and snow came, it was just too much for the sickly trees to take.

Some French guy thought they’d bring some coin…I recently learned that they were brought to the United States in the 1860’s by a scientist who was hoping to use them as a silk worm. This experiment failed and the larvae were somehow introduced into the wild. These worms have proved to be quite invasive and continue to expand and devour woodlands. The government’s solution to the problem has unfortunately been to treat trees with mass, aerial applications of Bacillus Thuringiensis (BT) in some states.

Why We Do Not to Use Bacillus Thuringiensis (BT) On Our Property

Bacillus Thuringiensis (BT) is a biological pesticide that attacks gypsy moths in the larva state. It is harmless to birds, spiders, wasps and natural predators of “other larvae” (remember, none of these eat the gypsy moth larvae) but it IS harmful to the “other larvae” who may be in the area. For instance, we have a healthy population of butterflies and other moths who are not only pretty, but provide essential pollination services and are an important food source to our local animal population.

While BT can do a great job to get the gypsy moth issue under control, multiple applications would likely need to be administered and it would need to be sprayed very carefully to avoid killing any beneficial insects. This might be a good choice for some people, but we were not comfortable using it. Most of our trees are over 20 feet tall and, to do a good job, the BT needs to cover most of the canopy of the impacted trees. It would be very difficult to make sure that we were not harming other beneficial insects.

We are hoping that a mass spraying of BT will not take place in our area. While gypsy moth damage is devastating to local trees, especially the oak tree, there will inevitably be harm done to other “good” larvae who are inadvertently treated with the bacterium. The situation is not a good one, especially because the gypsy moth population was out of control last year, but hopefully sharing our environmentally friendly tips will help on some level.

Environmentally Friendly Tips & Treatments…

Wear Gloves and Protect Your Skin

  • You do not want to touch the caterpillars, because their hair can irritate your skin.
  • I wear a collared shirt or wrap a bandana around my neck

Understand Their Habits & Act Accordingly

  • The larvae repel down in the morning
  • The larvae climb up the tree in the evening
  • The larvae eat the leaves of particular trees for weeks (May – June) and then they cocoon in the pupa state.
  • They will emerge from the pupa state as a fluttering and mostly flightless tan moth. The moth will breed and lay eggs on trees between June and July, and the egg masses will overwinter.
  • The whole process will start over the following April, when the tiny worms emerge again.

How We Waged War in the Most Environmentally Friendly Way We Could

  • In the winter, we located the egg sacks and destroyed them by scraping them into a container and soaking them in warm, soapy water.
  • Long handle brooms to collect the caterpillars and drown them in a bucket of sudsy water. We use environmentally friendly, biodegradable dish detergent.
  • Tape (at least 2 inches wide) and sticky substance wrapped around the infested trees. The caterpillars who are not caught and dunked will become trapped in the sticky substance. We like to use the brand Tanglefoot as our sticky substance, as it contains no harmful chemicals or pesticides. We are using a wide duct tape as the base to spread the Tanglefoot this year. You do not want to spread it directly onto the tree because that could harm the bark.
  • In the summer and spring, we will continue to look for egg sacks and destroy them in the same way we did over the winter.

Good luck to everyone else out there dealing with this issue. Even if you are not dealing with it yourself, please try to spread the word that there are environmentally friendly ways of treating the gypsy moth caterpillar issue on a small scale. Starting small may help to keep the issue from getting so big that it becomes necessary to spray BT indiscriminately over a large area.

For More Information…

There is a great article on the Purdue University extension website about the history of the gypsy moth in the United States if anyone is interested:


Here is another good article available on the National Associate of Conversation Districts website regarding the issue of spraying BT:





4 thoughts on “Invasive, Destructive & Downright Yucky. How Do We Kill Gypsy Moth Caterpillars Without BT?”

  1. We have a similar hairy caterpillar here in Australia. The method I use to reduce their numbers is to wrap a piece of hessian around the tree trunk because the caterpillars will hide in the folds during the day. The hessian can be dipped in a bucket of hot water and the caterpillars die. It’s staggering how often people have taken creatures to other countries for a particular reason only for those animals to become feral. We have rabbits, foxes, water buffalo, cane toads and pigs, just to name a few.


    1. Great tip! Thank you. We will set that up this season for sure. It is amazing how many issues are caused by introducing non-native species to a foreign habitat. Good luck with your worms and thanks again for your helpful information.

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