Stop or Prevent a Gypsy Moth Caterpillar Infestation In Late Spring/Early Summer

Along with Memorial Day cookouts and pollen-covered windshields, a sure sign of late spring and early summer is the gypsy moth caterpillar. When fully grown, they will be approximately 2 inches long, very hairy and have five pairs of blue dots followed by six pairs of red dots along its back. Beyond looking disgusting and crawling all over everything, they also cause severe damage to hardwood forests and urban landscapes in much of the Eastern United States. These pests defoliate a million or more forested acres annually.

Defoliation by gypsy moth caterpillars can weaken trees. By destroying their leaves, the trees are not able to manufacture food. Weakened trees are susceptible to bark beetles and root diseases that can kill them.

As if that weren’t bad enough, newly hatched caterpillars can also be a health hazard. Their hairs contain histamine and are highly allergenic!

Luckily, there are some simple steps that you can take to protect your trees from these hungry late-spring invaders.

Protect Trees From Caterpillars

Once temperatures are above 60 degrees Fahrenheit, caterpillars will hatch from the eggs laid the previous summer. Then they crawl up trees and out on the limbs to eat the leaves. These caterpillars primarily feed at night time to protect themselves from extreme heat and predators like birds. Even though you may not see them in action during the day, this does not mean that your yard is free of them.


One way to prevent gypsy moth caterpillars from eating your tree’s leaves is to block their climb on tree trunks.  Before entering the pupae stage, caterpillars will begin a routine of feeding at night, then climbing down the tree at dawn in search of a safe spot to rest for the remainder of the day.  At dusk they climb the trees again to feed.  You will know that caterpillars are in this stage when defoliation is severe enough to be noticed.

The Tanglefoot® product that Koopman carries is the perfect product to use.  Its adhesive composition traps the caterpillars as they try to crawl over it. Additionally, it is made from all natural ingredients, so no pesticides or chemicals are going to harm your trees!

Begin by wrapping two widths of Tanglefoot® tree wrap around the trunk of the tree up from the ground at about chest height. Be sure to tuck the wrap tightly into every fissure and crevice in the bark.

Then smear the Tanglefoot® around the center of the wrap, using a popsicle stick or a wooden shim so that you don’t get any of the product on you.

Before the long, the trapped caterpillars will begin to stack up. Scrape them off into a jar that contains a couple inches of water and some dish detergent. Though this takes some time, it is a highly effective method.

Caution: Don’t smear the Tanglefoot® directly on the tree, as it will discolor the bark and could cause damage.


Another method is to use a controlled spray to kill gypsy moth caterpillars. This is a particularly useful approach if you didn’t get your Tanglefoot barriers up early enough and caterpillars are already feeding in your trees. Correct timing and application are the most essential elements for success. Read and follow label directions exactly.

bonide gypsy moth solutions 3w1hThe Bonide products Thuricide®, Eight® and Captain Jack’s Dead Bug Brew® are all well suited for this purpose.

Thuricide® (also often referred to as “BT”) is most effectively applied when gypsy moth caterpillars are still small or at the first sign of infestation. Create a mix 4 teaspoons of Thuricide® per gallon of water, then apply using a pump sprayer. Apply the mix thoroughly to the upper and lower leaf surfaces, but not to the point of excessive runoff. Be sure to agitate the mix regularly while spraying. The treatment can be repeated in two weeks.

Eight® provides economical, contact and residual insect control for up to 4 weeks.  It may be applied to homes and other areas to stop infestations. It is available in concentrate, ready-to-use spray bottle, and hose-end sprayer formats. If using the concentrated format, use 1 Fl. oz. in 1 gal. of water.  Apply as a thorough spray, wetting leaves and branches to the dripping point. Try to penetrate dense foliage. Spray in the late afternoon or evening, when the temperature ranges from 50˚ to 75˚F and when there is little or no wind. Spray at the first sign of insects. Repeat as necessary; use intervals of 4-8 days. Do not exceed 16 applications per season.

Captain Jack’s Dead Bug Brew® contains Spinosad, a naturally-derived insecticide used around the world for the control of a wide variety of insect pests. It has even been approved for use in organic agriculture by numerous national and international certifications!  It is available in concentrate, ready-to-use spray bottle, and hose-end sprayer formats.  If using the concentrated form, make sure to carefully follow the mixing guidelines on the product label. Using a pump sprayer, apply the mix uniformly onto the leaves to the point of runoff. Uniform coverage of upper and lower leaf surfaces is essential for effective insect control.

Honey bees are vital to life as we know it, therefore we always need to be aware of our actions on these little pollinators! Both the organic and synthetic solutions above are deemed safe for bees. However, always follow these tips:

1) Never spray anything on open or budding flowers.
2) Never spray anything where bees are active.
3) Ideally spray late in the day after bees are gone and the solution has time to dry before potential contact with bees.

If you have a large area you will need to spray, you can also rent the Stihl® SR430 Backpack Sprayer from either our Uxbridge or Grafton Rental Departments.

This gasoline-powered liquid-only backpack sprayer delivers a large spraying range, reducing the time it takes you to treat large areas. Its high performance pressure pump provides a constant flow of product with no loss of pressure, regardless of the spray angle. While the engine is running, the pump also continuously mixes and agitates the tank contents, delivering a more consistent application of product.

Encourage Birds To Visit Your Propertybird eat caterpillar

There are a variety of bird species known to prey on gypsy moth caterpillars, including bluejays, blackbirds, nuthatches, cuckoos, chickadees, towhees, vireos, northern orioles, robins, catbirds. By selecting a high-quality Blue Seal bird feed from Koopman that these species prefer to consume, you can draw these birds to your property. Once in the yard, these birds will find a juicy caterpillar to be a delectable treat.

Interrupt The Gypsy Moth Life Cycle

Throughout the rest of the year, there are several easy preventative steps you can take to disrupt the gypsy moth life cycle, especially destroying their egg masses in order to prevent your property from being overrun with newly hatched caterpillars during the next spring.

gypsy moth egg massKeep Your Yard As Clean As Possible Year Round

Remove piles of old wood, dead branches, stumps, etc., where the adult female moth is likely to lay egg masses in the late summer. Also, remove any hiding places on the trees themselves; ivy, bark flaps and dead branches.  Carefully inspect buildings such as toolsheds, garages, and tree houses, as well as stone walls, wood piles, and fencing for hidden egg masses.

Destroy Any Egg Masses In Early Spring

NOW is your first chance to stop the destructive Gypsy Moth Caterpillar!  Use Bonide’s Organic All Seasons Oil and cover all visible egg sacks in your area. Do not remove the egg sacks from the tree, spray them right where they are. All Seasons Oil can be used as a concentrate (then added to water and sprayed) or also available in a ‘ready to spray’ and a ‘ready to use’.  The All Seasons Oil is a surfactant and will coat the eggs eliminating the oxygen and prevent the eggs from hatching.

To prevent caterpillars from devouring your tree’s leaves, this will need to be done before mid-AprilYour ounce of prevention by mid-April can prevent the mess of chewed up leaves and gypsy moth waste.

Destroy Any New Egg Masses In Late Summer

If you weren’t able to prevent caterpillars from emerging from their egg masses in May, eating all your leaves, and then going into their pupae stage, you can still take action to destroy the egg masses that will appear in late summer.   You can use the same products and procedures as listed above in the instruction for destroying egg masses in spring.

Remember, every egg mass that you soak today will make a difference going forward!! 
If you are able to treat as many egg masses as possible, you can prevent next spring’s generation of caterpillars from hatching. Good luck!!!

Read the full blog here


Wrap Up

By attacking the gyspy moth at each stage of its life cycle, you can begin to make headway against an established population. To stock up on all of the products you’ll need to combat these hungry, hairy invaders, stop by your local Koopman Lumber store! We’ve got the friendliest, most knowledgeable staff around. We’ll be glad to help you arm yourself with the tools and know-how you need to protect your trees.