Gypsy Moth Frequently Asked Questions

Gypsy moths are eating my trees. What can I do?

This year, if you have a severe gypsy moth caterpillar problem in your forest, there is little you can do to prevent defoliation unless you have your property sprayed. In May, you can spray an insecticide (see below). After May, however, caterpillars are too large and spraying is ineffective.

If spraying is not an option, there are a few things property owners can do to minimize damage and help control the population on a small number of trees. One method is to tie a piece of burlap around the bole of the tree at breast height. When caterpillars emerge they will congregate under the burlap where they can be removed and killed.

To help important landscape trees after defoliation, using fertilizer spikes and watering thoroughly during dry periods may help the tree survive.

For next year, for a small number of trees, landowners can scrape off egg masses within reach. If masses are all over the tree, this practice probably won't be effective.

How do gypsy moths affect my trees? Will my trees die?

Gypsy moth caterpillars feed on the tree's leaves, affecting its ability to photosynthesize.

A single defoliation will not kill a tree unless the tree is already under stress. Trees impacted by the caterpillars will most likely push out a new set of leaves in several weeks. Two or three years of defoliation in a row will severely impact a tree, causing dieback and increasing its susceptibility to root diseases and attack by other insects.

What tree species do gypsy moths feed on?

Gypsy moths impact mostly oak trees. They also feed on alder, apple, aspen, basswood, beech, birch, boxelder, hawthorn, larch, willows and witchhazel. Larger caterpillars also feed on pine and hemlock.

How do I sign up my property for next year's spray program?

Property owners impacted by gypsy moth this year should call their county Gypsy Moth Coordinator. (In most cases it is a staff member within the county Conservation District.) You can check the list of county coordinators.

To qualify for the DCNR coordinated spraying program, landowners need a minimum of 23 forested acres around a residential structure. Not all 23 acres need to be owned by the concerned landowner. Contact your county coordinator to request a survey of your area, and the coordinator will explain how the spray zone around a residential structure is determined.

When will my area be sprayed?

Spraying will begin in early May and will be completed soon after Memorial Day. Operations will begin in southern Pennsylvania and move northward. Contact your county gypsy moth coordinator for specific information about your area. You can also check the DCNR Forestry website for spray program updates. Spray schedules can change due to weather conditions and other operational constraints.

What insecticide is used in the DCNR spray program?

DCNR contracts for the use of a biological control insecticide, commonly called Bt (Bacillus thuringiensis var. kurstaki). The commercial name is FORAY 76B. Bt is a bacteria that is sprayed on the tree’s foliage. The bacteria remains effective for 7 to 10 days. Caterpillars ingest the bacteria when they feed on the foliage. The bacteria can take several days to take effect. Not all caterpillars die as a result of spraying. Bt can only affect certain leaf-eating caterpillars that are in the larval stage at the time of spraying.

Bt is sprayed at a rate of one-half gallon per acre and is not mixed with any other chemicals or any other material.

Is Bt harmful to people or pets?

No. Some people, however, are sensitive to insecticides. Some individuals may develop minor irritation of the skin, eyes or respiratory tract. The effects are relatively mild and transient and are usually seen only in staff working on the project. If you have any concerns you should contact your physician.

My automobile was sprayed. What can I do to remove the tiny spots?

There is nothing in FORAY that will cause damage to automobile finishes. This product is formulated to stick to the surface of leaves when it dries. Therefore, it is easiest to remove from any surface while it is still wet. To remove dried Foray from any surface, simply soak the dried droplets with water and then sponge or wipe with a soft cloth. A cleaning product normally labeled for car washing may be needed if the dried spray has been on the surface for awhile. The sooner the surface is cleaned, the easier it will be to remove the spray droplets. If the automobile's paint is old, oxidized, and/or severely weathered, Foray will adhere to this porous surface; it will be more difficult to remove. A large bath towel may be soaked and placed upon the painted surfaces for several minutes to allow the Foray deposits to become rehydrated. This will make the spray deposit easier to remove. In extreme cases, several soakings with a wet towel may be required.

I am not included in the state spray program in 2009. How can I get my property sprayed this year?

Property owners not included in the state-coordinated spraying program this year can contract privately with either aerial or ground applicators. Partnering with neighbors can make the cost more affordable. Ask the applicator about what products they will spray. Some insecticides will also kill beneficial insects. In addition to Bt, other insecticides used by private applicators are DIMILIN and CONFIRM. Both of these insecticides must also be applied to the foliage and be eaten by the caterpillars to be effective.

Check the list of private aerial applicators. Also look in the phone book for Pest Control Services, Tree Service, or ISA Certified Arborists for ground applications.

Will gypsy moths always be a problem in PA's forest?

Gypsy moths are established in Pennsylvania and will be here for a long time. Gypsy moth infestations are cyclical; there are peaks and valleys in the population. Outbreaks usually last about 3 years with approximately 5 to 10 years between. Wet springs help keep populations lower because they encourage the growth of a fungus that impacts gypsy moths. Dry springs give gypsy moths the advantage.

Gypsy moth populations in the Poconos are still a problem but are in decline in some areas due to viral and fungal diseases. The outbreak in the central and south-central portions of the state are in their third year and noticeable caterpillar mortality was observed in the south-central counties due to disease in 2008. However, we expect another year of defoliation in 2009 especially in the central part of the state.

Online Resources:

www.fs.fed.us/ne/morgantown/4557/gmoth/

www.na.fs.fed.us/spfo/pubs/fidls/gypsymoth/gypsy.htm

www.na.fs.fed.us/spfo/pubs/pest_al/gm/gm.htm

www.aphis.usda.gov/plant_health/plant_pest_info/gypsy_moth/index.shtml

www.invasivespeciesinfo.gov/animals/eurogypsymoth.shtml

www.pittsgrovetownship.com/GypsyMoth2008/76BLabel.pdf

www.pittsgrovetownship.com/GypsyMoth2008/76BMSDS.pdf

Foray Forestry Manual from Valent Biosciences

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