GYPSY MOTHS AND TAKOMA PARK

February 2001

The gypsy moth is considered a serious threat to forest, shade, and fruit trees and ornamentals in our area. In infested areas, populations fluctuate over time in response to various factors. When gypsy moth populations are higher, the threat of significant defoliation occurs. Damaging levels of defoliation usually occur in areas where oaks are the most abundant tree. When heavy infestations occur, economic and ecological impacts can occur. Also, the numerous caterpillars become a nuisance to people. Proper identification of the insect and various control measures can help reduce gypsy moth infestations and the damage they cause.

Gypsy moths are often confused with other common caterpillars, including tent caterpillars, that emerge during the spring and summer. Gypsy moth egg masses are 3/4 to 1 ½ inches long and are covered with fine yellow or buff colored hairs from the female's abdomen which then turn gray. Gypsy moths overwinter in these yellow egg masses that are attached to tree trunks, underside of branches, on the ground under loose stones, boards, firewood, lawn furniture, birdhouse, the sides of houses and picket fences.

Gypsy moth larvae hatch during May and June. These newly hatched larvae are approximately 1 millimeter in length (first instar) and will remain on the egg mass for several days before they crawl into treetops to feed. Similar to the cankerworm, some larvae will spin a strand of silk thread and dangle until it is moved back and forth by the wind. After the first instar, larva feeds for several days it will shed its skin and grow to about 10 millimeters in length (second instar). The second instar can be identified by its black color with a visible light brown band down its back. The third instar is approximately 15 millimeters in length and can be identified by its ten pairs of blue dots down its back. Several instars may be present at one time and the second and third instars will feed in the treetops during the day creating damage that looks like shotgun holes. This usually occurs during most of May.

During the fourth instar, the caterpillar is approximately 25 millimeters in length and are black with spiny hairs and colored spots. The first five pairs of spots remain blue while the last six pairs of spots turn red. It is at this stage that the eating habits of the caterpillar change. They will hide on trees during the day in shaded areas and will crawl up the trees to feed at night. Some caterpillars will even climb all the way down the tree to finding hiding places on the ground during the day. At dusk, they will return to the treetop to feed all night. This feeding activity usually occurs in late May. In June, the caterpillars begin to eat entire leaves and can defoliate a tree when high concentrations are feeding.

Male caterpillars reach their maturity during their fifth and final instar while female caterpillars reach maturity during a sixth instar. These mature caterpillars feed ravenously in June and are responsible for most of the defoliation. In late June, when there is a large gypsy moth population, the mature caterpillars will leave defoliated trees in search of more food or hiding places to pupate. They will often be spotted on houses, decks, picket fences, lawn furniture and even in houses. This activity usually occurs until early July.

Adult moths appear from their pupal cases around late June to early July. The female moth, which can not fly, will then crawl up the tree to attract a male, mate and deposit her eggs. This usually occurs from late June to the middle of July. Neither the male nor the female moth eats leaves. The adults live only for a short period of time.

When planting new trees in Takoma Park, you may want to think about planting species that are generally resistant to gypsy moth infestations. Trees which gypsy moths prefer to eat include oak, apple, willow, and birch to name a few. Examples of trees which gypsy moths generally do not prefer to eat are ash, sycamore and black locust.

Another method to control gypsy moth populations is to scrape off and destroy egg masses from all infested trees and structures. Egg masses should be removed and destroyed before April when the eggs begin to hatch. Wear gloves to protect yourself from the insect hairs. Egg masses should be placed in bags for disposal or into a solution of soapy water. It is helpful to notify the City of Takoma Park or, more importantly, the Maryland Department of Agriculture (MDA) when removing egg masses. The MDA performs egg counts for gypsy moths every fall so it is very important to notify them when egg masses are located and/or removed so their counts will be accurate.

There are two banding methods that can destroy gypsy moths. The first technique is the sticky barrier band. This prevents the caterpillars from crawling up the trunks of the trees into the canopies where they feed. This sticky band should be in place before the eggs hatch, before the end of March, and must be maintained all season. This barrier band can prevent the primary invasion of newly hatched caterpillars from those egg masses found on houses, picket fences, leaf litter, woodpiles and lawn furniture. It will also prevent secondary invasions of caterpillars including those caterpillars that dangle from silk threads to be moved by the wind, those that fall out of the tree due to wind and rain, and those that migrate out of already defoliated trees in search of food.

Homeowners can either buy a commercial sticky barrier band or make a homemade band. Commercial sticky barrier bands may be hard to find as this product comes and goes depending on current gypsy moth trends. One brand available for sale to Takoma Park residents is Repel'M III®. Homeowners are also encouraged to contact their local hardware store and/or garden center for a similar product.

If commercial sticky barrier bands are hard to find, one can be made by using duck tape and tanglefoot. Simply apply the duck tape around the tree so the sticky side will adhere to the bark. Then take a stick, or tongue depressor, and apply the tanglefoot to the duct tape. Tanglefoot can also be found at home and garden centers. The caterpillars will get stuck in the tanglefoot while they are attempting to crawl back into the treetops. Do not apply tanglefoot directly on the tree.The second technique in combating gypsy moth infestations is burlap bands. This creates a resting and hiding place for the larger caterpillars that crawl down the tree during the day to rest. This burlap band should be in place before the end of April and must be maintained all season.

Simply wrap the tree with burlap that is at least 18 inches wide and long enough to wrap completely around the tree and to overlap slightly. This burlap band should be placed approximately 6 to 12 inches above the sticky barrier band. Place string or twine in the middle of the burlap strip and fold the top portion over, creating a 9 inch flap. AT LEAST ONCE A DAY inspect the underneath side of the burlap and remove and destroy any and all caterpillars, pupae, moths and/or egg masses. Using gloves or tweezers to remove the insects, which is recommended as some people are allergic to the caterpillar's irritant hairs, place the caterpillars in a bucket of soapy water to destroy them. Then place the destroyed caterpillars in a bag and place in the garbage.

When using burlap bands, it is imperative that the band be inspected AT LEAST ONCE A DAY. Burlap bands provide a resting and hiding place for the insect that can permit populations to build if the egg masses, caterpillars, pupae and moths are not removed. Homeowners who are not willing to check the burlap band on a regular basis and destroy the insects should not use the burlap band. Burlap bands that are not routinely maintained will do more harm to a tree than good.The use of sticky barrier bands is an effective technique to manage gypsy moth infestations in individual settings. They protect foliage by reducing the total number of caterpillars reaching the treetops to feed. Burlap bands are also a gypsy moth management tool if they are maintained and, more importantly, inspected on a regular basis. Both methods can provide additional protection even if your property is sprayed for gypsy moths. The City of Takoma Park Department of Public Works will sell burlap and the commercial gypsy moth tape Repel'M III®. Takoma Park residents can purchase one roll of Repel'M III® for $7.00 and three yards of burlap for $3.00. Items will be on sale at the Finance Department located in the Municipal Building at 7500 Maple Ave.

Gypsy moth populations can also be controlled with the use of insecticides. Every fall since the early 1980's, staff members from the Maryland Department of Agriculture (MDA) have conducted gypsy moth egg counts in the City of Takoma Park. During the fall and winter of 2000, the MDA performed their annual gypsy moth egg count in the City and found an area where there is a significant threat of defoliation. As the result, an area of 400 to 450 acres in the City of Takoma Park will be treated via aerial spraying in May 2001. Aerial spraying is a cooperative

effort to control the gypsy moth between Federal, state and county agencies. The insecticide used for this spraying will be Bacillus thuringiensis, a natural occurring spore-forming bacteria that during sporulation, produces a toxic protein. When ingested by the gypsy moth larvae, this protein will kill the caterpillar. [Map of areas to be sprayed.]

The MDA will notify those property owners inside the 400 to 450 acre area, as well as those homeowners within 250 feet of the spray area (buffer zone), with a map of the area and a letter describing the spraying. MDA representatives will review the plans for gypsy moth spraying at the Takoma Park Municipal Building on Monday, March 12, 2001 during the Council meeting. They will discuss and answer questions and/or concerns regarding their egg count results and the aerial spraying program.

For the history of the gypsy moth, some great pictures and the like,
please check

USDA Forest Service gypsy moth pages
Virginia Tech gypsy moth server
Delaware Cooperative Extension's Gypsy Moth Homepage
Oregon's Department of Agriculture gypsy moth page

Text from Todd Nelson, City Arborist.
Pictures on this page courtesy of Maryland Department of Agriculture and Virginia Tech.