What Can I do if I have Gypsy Moth on my Property?

Cultural Control

One of the most basic things you can do to reduce gypsy moth damage is to plant a variety of tree and shrub species on your property, taking care to include some plants that are less preferred by gypsy moth. This can be difficult, as gypsy moth feeds on over 300 species of trees and shrubs in Pennsylvania. Gypsy moth caterpillars prefer to eat oak, apple, alder, aspen, basswood, birch, poplar, willow, hawthorn, hemlock, tamarack (larch), pine, spruce, and witch hazel. Plants that gypsy moth usually avoids include ash, butternut, black walnut, locust, sycamore, yellow poplar (tulip tree), ferns, mountain laurel, redbud and rhododendron. The DCNR encourages you to plant species that are native to Pennsylvania on your property to avoid the escape of invasive plants into wild habitat where they may threaten wildlife. Remember not to go overboard by planting too much of any one species on your property. Even if it is not favored by gypsy moth, these plants may be attacked by other invasive species that might someday arrive in Pennsylvania.

Another simple thing landowners can do to avoid gypsy moth damage is to keep the species they plant healthy. Sick or stressed trees are easy prey for gypsy moth caterpillars, because their natural chemical insect defenses are compromised. Healthy, vigorous plants tend to resist attack and have a better chance of surviving a severe gypsy moth infestation. You can keep your plants healthy by irrigating them in drought conditions. Most trees need about an inch of water per week during the growing season. You can have your soil tested at your local extension office to determine if fertilization is recommended. If so, apply fertilizer to trees in early spring to ensure an adequate supply of nutrients for vigorous growth. Pruning trees and shrubs of broken, dead and diseased branches can also keep them healthy. Late March or early April is a good time to prune many trees and shrubs, provided that flowering has concluded. Lawnmowers and weed killers can negatively affect your trees and shrubs by physically or chemically damaging roots. Remove grass around the base of your landscape plants and apply a layer of mulch around them. This will help the trees retain moisture and provide a buffer from your lawnmower.

Finally, landowners should remove unused objects in your yard that may provide shelter for gypsy moths, such as signs, tires, lumber or junk piles, or cinder blocks. Gypsy moth parasites and predators such as mice, shrews, ground beetles, birds, flies, and wasps work more efficiently when their prey is out in the open. Therefore, removing these artificial resting places will aid natural enemies in reducing gypsy moth populations on your property.

Mechanical Control

Mechanical gypsy moth controls do not involve the use of insecticides or natural enemies. Mechanical techniques that landowners with a limited number of susceptible trees can use to control gypsy moth include burlap banding to remove caterpillars, scraping, destroying female moths and destroying egg masses.

Burlap bands are actually traps designed to provide sheltered resting sites for caterpillars. This practice capitalizes on the behavior of older gypsy moth caterpillars to migrate to the lower bole of the tree during the day to rest in a sheltered area, while they feed at night in the tree canopies (except in extreme outbreak conditions). The burlap band is a 12 - 18 inch wide band of burlap cut a little longer than the distance around the tree. Wrap the burlap around the tree at your chest height, overlapping at the ends, and tie securely around the middle with twine or nylon cord. Fold the top half of the band down over the bottom to form a loose band. Band all of the preferred gypsy moth food trees on your property. Check under the band each day by lifting the band and scooping all resting gypsy moth caterpillars into a jar of detergent solution using a spoon. Landowners should apply burlap bands to trees around mid-May and continue to service them until around late July.

Because female gypsy moths cannot fly, they must crawl from pupation sites to mate and lay their egg masses. Search for white female moths on tree trunks, loose bark flaps, tree houses, bird feeders, picnic tables and other dry, sheltered areas from early July until mid-August before they lay their eggs. Use a spoon to push gypsy moth females into a jar of detergent solution.

Each nickel to quarter-sized egg mass that you destroy eliminates from 500 to 1,000 caterpillars from next year's gypsy moth population. Search for egg masses in the same sheltered areas preferred by female moths any time between July and the following April, since eggs don't usually hatch until late April in southern Pennsylvania. Use a spoon to scrape egg masses off surfaces where they are attached. It is important not to leave scraped egg masses on the ground, as eggs can survive under the snow in the winter. Eggs should be placed in a jar of detergent solution or burned. Do not paint egg masses residing on tree trunks with oil, grease, tar, or creosote, because this can soak through the bark and kill living tree tissue. Allow detergent solution used to collect caterpillars, adult females and egg masses to soak at least a day before discarding to ensure that all collected gypsy moths have been killed.

Gypsy moth traps use attractive chemicals called pheromones to lure and capture brown male moths. Unfortunately, these traps are not effective in controlling this insect. They should only be used for monitoring populations during late June and early July. If you collect 50 or more moths in each trap, you should search for egg masses.

Although none of the mechanical methods mentioned above are likely to be effective during peak outbreaks of gypsy moth, they may be a cost-effective way to decrease defoliation on your property during periods when populations are low to moderate.

Chemical Control

Chemical control may be the best way to control gypsy moth in situations where populations are extremely high or when large tracts of land need management. Trees or shrubs less than fifty feet in height may be sprayed with a backpack mistblower or high pressure garden sprayer. Insecticides containing BT (i.e, Dipel, Thuricide, Caterpillar Attack) are a widely available and effective treatment for gypsy moth. It is important that the product you choose includes the active ingredient "Bacillus thuringiensis, var. kurstaki" rather than "israelensis," "San Diego," or "tenebrionis," as these products will only work against fly or beetle larvae, NOT gypsy moth. Follow label instructions for application of gypsy moth chemicals exactly.

For taller trees, landowners may need to hire a licensed pesticide applicator to treat for gypsy moth. Call several reputable tree service companies for pricing, ask for references, and be sure to check with local clients they have served.

During gypsy moth outbreaks, the Commonwealth of Pennsylvania, in cooperation with the US Forest Service and participating counties, conducts a spray program for qualifying applicants who live in forested residential communities. Currently BT and the chemical form of a gypsy moth virus known as Gypchek, are the only chemical controls used in this program in Pennsylvania. Contact your county gypsy moth program coordinator through the county commissioner's office for details on the program.

Participate in the Gypsy Moth Suppression Program.

For private landowners, the County authority will determine if a property will qualify to participate in the gypsy moth suppression program. Landowners must contact their County gypsy moth coordinator by July 15 to have their property evaluated, and to be considered for inclusion in the following year's gypsy moth suppression program. Properties that receive treatment in any given years gypsy moth suppression program are evaluated and approved in the year that precedes a gypsy moth suppression program. For example, private forested areas sprayed in 2008, were evaluated and approved by their County authority in August of 2007. You can check the listing of County gypsy moth coordinators

Gypsy Moth Links

Penn State Extension Gypsy Moth Fact sheet

USDA Forest Service Gypsy Moth Web page

USDA Forest Service Gypsy Moth Leaflet

Gypsy Moth Home

Forest Pest Management Home