Getting Rid of Gypsy Moths: Preventing Next Year’s Generation Of Caterpillars

After gypsy moth caterpillars have eaten their way through May and June, it can be tempting to think that you’re in the clear. Sure, the creepy hairy crawlers are no longer devouring your tree’s leaves and are no longer depositing shredded leaves and other matter all over your yard.

But in reality, all that has happened is a shift to a different stage in their life cycle. Outside, you’ll begin to see gypsy moths emerging and flitting all over the place. To avoid another devastating feeding frenzy come next May and June, you need to remain on the offensive.

From Caterpillar To Moth

The Gypsy Moth Pupae Stage

The Pupae Stage

Once late June rolls around, the gypsy moth caterpillar enters its pupal (transitional) stage. The pupae are dark brown, shell-like cases approximately two inches long and covered with hairs. They are primarily located in sheltered areas such as crevices in tree bark or leaf litter.

During periods when population numbers are dense, pupation is not restricted to locations where larvae rested. Pupation will take place in sheltered and non-sheltered locations, even exposed on the trunks of trees or the foliage of non-host trees.

Male (L) and Female (R) adult Gypsy Moths

Male (L) and Female (R) adult Gypsy Moths

In 10 to 14 days, adult moths will emerge from the pupae. The male gypsy moth emerges first, flying in rapid zigzag patterns searching for females.   Males, which with a 1.5-inch wing span – are smaller than females.  Male moths are dark-brown and have feathery antennae.

Then the females, laden with unfertilized eggs, emerge. Females have white to cream-colored wings, a tan body, and a two-inch wingspan. They emit a chemical substance called a pheromone that attracts the males.

Click here to learn how to kill gypsy moth caterpillars

Interrupting The Gypsy Moth Life Cycle

At this stage in the game, the goal is to prevent the current generation from birthing the next generation.  If they can successfully mate with a male moth, females lay between 500 to 1,000 eggs. That’s quite a batch of leaf-chewers who will hatch next spring with a voracious appetite!

Since it is the male gypsy moths that fly, the goal is to trap and eliminate as many of them as possible before they can find a female to mate with. The key is to use a device that will attract them using ultraviolet light.

Stinger Insect Zapper®

Stinger Insect Zapper

Stinger Insect Zapper®

One option for eliminating the male gypsy moth population is the Stinger Insect Zapper®. The ultraviolet light given off by this device is within the luminescent range proven effective to lure flying insects. Insects are attracted to the light and killed as they contact the electrically charged inner grid area. These insects then fall through the open base onto the ground.  The protective outer cage helps prevents pets, birds, butterflies and children’s fingers from contacting the charged grids.

When selecting a location to place the Insect Zapper®, keep in mind that the idea is to draw the moths to the unit, so do not put the unit near human activity. Instead, locate the zapper in a location about 25 feet away from the area you are trying to protect.  The Insect Zapper® is designed to protect an area of up to 1/2 acre.


Another option is using a Dynatrap. Like the Insect Zapper®, it uses ultraviolet light to attract flying insects.  The Dynatrap can attract and capture flying insects in both daylight and nighttime and is designed to run 24/7.

Dynatrap Visiglo®

Dynatrap Visiglo®

Also, it features a vacuum action fan that helps to collect in insects that it has lured close to it. The powerful, yet whisper-quiet fan draws attracted insects into the retaining cage. It then keeps those insects from escaping using the vacuum action created by the continuous cycle of the fan. The insects are trapped and will become dehydrated and die.

The retaining cage can be removed, allowing the contents to be periodically emptied into the trash. The screened material on the retaining cage allows what has been trapped in the unit to be seen, and alerting you when the cage needs to be emptied.

Destroying the Eggs


A gypsy moth egg mass on tree bark

If you don’t manage to kill the moths before they’re able to mate (by late July) then you will want to be on the lookout for egg masses. Smaller egg masses (about 0.5 inches long) might contain as few as 75 to 100 eggs, while larger egg masses (up to 1.5 inches long) can contain 700 to 1000 eggs!

The masses will appear until the end of July when the female gypsy moths have all mostly laid their eggs and died, or failed to mate and died anyway.  They are commonly found on trees, lawn furniture, foundations, picnic tables, fallen logs, wood piles, etc.

lichen and fungus in tree bark

Lichen and fungus in bark

The egg masses appear to be a buff color when they’re first laid and will bleach out over the winter when exposed to sunlight and weathering. The eggs can hatch as early as mid-March, so make sure you’re finished by then!

Helpful Hint:  Female gypsy moths like to lay their eggs in areas of tree bark that have moss, fungus, and lichen on it.  These blended colors provide effective camouflage for egg masses. Be sure to inspect these areas carefully so that you don’t miss any egg masses.


Scraping the Eggs

One way to take care of egg masses that are within reach is to scrape them into a container and then drown them in a soapy solution.

Caution:  Wear a safety mask, safety glasses, and gloves when scraping egg masses. This action can expose the scraper to allergenic hairs covering the mass.

Start by filling a 5-gallon bucket 1/2 full with water, and then adding a generous amount of dish soap to it. Then, locate as many of the egg masses as you can find.  Scrape the egg masses off of the surface they’re attached to with a putty knife or similar tool. Collect them in a small bucket, pail or anything that will make it easy to transport them back to your bucket.  Then dump them into the soapy water.

Horticultural Spray

If you don’t want to scrape away a bunch of gross egg masses, you can also saturate the egg masses using a pump sprayer. Spray with a product that contains horticultural oil, such as Bonide’s All Seasons Horticultural Spray Oil® or Rose Rx®.

Treat individual egg masses until they are completely saturated with the solution. You don’t have to worry about removing the masses afterward when using this method.

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.

Blast Eggs and Egg-Laying Moths Off of Trees

For egg masses higher up in trees – usually on the underside of limbs where they meet the trunk – scrapingLittle Big shot logo made in USA by veterans badge and treating with horticultural spray aren’t realistic options.  Your only remaining option is to blast any egg masses and egg-laying female gypsy moths off of the tree with a high-pressure spray nozzle.  We’ve found the Little Big Shot® spray nozzle to be extremely effective in this effort.

Egg-laying female moths may survive your initial blast of water.  They will make their way back to the tree and attempt to climb it again and lay more eggs.  You’ll need to repeat this process over a few days until the all of the female moths have been killed.

Caution: Never burn egg masses. Wear a safety mask when working scraping eggs as the action can expose the scraper to allergenic hairs covering the mass.

Learn more about destroying Caterpillar Egg Masses

 Wrap Up

At Koopman Lumber, we have the products you need to deal with the swarms of gypsy moths flitting around your yard. Stop by your local Koopman Lumber store today!