Species

Lymantria dispar
Class: Insecta
Order: Lepidoptera

Related species
Gypsy Moths can be mistaken for eastern tent caterpillars, forest tent caterpillars, and tussock moths, all of which are defoliating insects.

Host/Site

Gypsy moths, though present throughout the US, are more prominent in the south and northeast US. They feed on tree foliage, most commonly oak, aspen, willow, birch, apple, and basswood trees. They have also been reported feeding on an additional 300 tree species.

As recently as 2009, the Washington State Department of Agriculture claims to have eradicated every gypsy moth infestation from becoming established in the state. If a large infestation is located over multiple acres, it is recommended to contact the WSDA.

Depending on the size of the tree, the larvae and caterpillars can be out of reach within the canopy. Developing larvae feed on leaves during the day and are dormant in the canopy at night. Adult larvae feed at night. In the daytime they move down the tree, resting in places such as crevices in the bark and shrubbery on the ground.

Identification

Appearance
Gypsy moths have multiple appearances throughout their development. Young larvae can be dark in color with orange coloration on the back. Most visible, however, are older larvae that have blue and red tubercles along their backsides. They also have black markings on the head that resemble eyespots.

Once adult moths emerge, males can be distinguished by their brown coloration with black markings on wings and feathery antennae.

Female moths are white, have brown markings, and do not have feathery antennae like males.

Indicators
The most vivid indicator of gypsy moth caterpillars is the blue and red tubercles that run down the backsides of adult caterpillars.

For moths, locate both white and brown winged moths in the same region. This will indicate male and female gypsy moths and suggest mating for next season is underway.

Life Cycle
Gypsy moth's have a single generation cycle per year. Egg masses that have overwintered on tree trunks and branches begin to hatch usually in early spring. Egg masses are brownish beige in color and can be covered with hair from the egg-laying female.

Once larvae hatch, they begin to eat foliage and grow over an inch in length as adult caterpillars. After 4-6 weeks, the larvae undergo a two week transformation from pupae to adult moths.

Female moths do not fly, but begin preparing for mating. Females release pheromone, a chemical used to attract male moths. After mating, females lay the egg mass that can contain one thousand eggs. Both male and female moths stop eating and die off once egg masses are laid. These eggs last through winter and hatch the following spring.

Natural Enemies

Gypsy moths do have natural enemies, though they are not relied upon for population eradication. Over twenty insect parasitoids and predators can limit gypsy moth populations. A nucleopolyhedrosis virus contaminates populations while an entomopathogenic fungus species also has lessened populations in the US.

The most effective vertebrate for control includes the white-footed mouse.

Monitoring

Look for egg masses, larvae, caterpillars, or moths on the trunks and in the branches of trees prone to outbreaks in Spring when they are reemerging.

Action Threshold

Action must be taken immediately if gypsy moth infestation is noticed. Without intervention, trees can be defoliated completely. This cannot happen in a single season, but gypsy moth hatching over 2-3 consecutive years or in conjunction with drought could lead to tree mortality.

If a tree is defoliated heavily in the first year of infestation, it can still live. Healthy trees can live without 30 percent of its foliage for several years. Neglecting a gypsy moth infestation, however, can lead to over 50 percent of defoliation and eventual death.

Cultural and Physical Controls

For a small infestation (1-3 trees), physical controls are recommended.

For caterpillars, tree banding is used to trap caterpillars and larvae that are trying to make their way along tree trunks.
Wrap burlap around a section of the trunk during Spring. Older larvae will collect beneath the burlap mistaking it for a shelter. Collect the caterpillars daily, and place them in soapy water before disposing them.

Sticky bands can also be used, although burlap is recommended first. Sticky bands are composed of duct tape around the trunk with a sticky substance applied to the surface of the tape.

For egg masses, spraying a 50/50 solution of soybean oil and water reduces the eggs ability to hatch. Sprays should be frequent and coupled with physical removal and destruction of egg masses before hatching, if possible.

However, banding and physical removal of eggs are not feasible for large areas of infestation. Again, contact your state's dept. of Agriculture for further instruction.

Biological Controls

Bacillus thuringiensis (Bt) bacteria, when sprayed on an infected tree, interferes with the digestive system of the caterpillars, leading to death within 7- 10 days.

Entomophaga maimaiga is a fungal disease that is effective in reducing gypsy moth populations.

For higher population densities, the gypsy moth nucleopolyhedrosis virus (NPV) can be used. See Chemical Controls below.

Also, a tiny wasp, Ooencyrtus kuvanae, lays its eggs in gypsy moth eggs within egg mass. Wasps hatch instead of the moth larvae.

Chemical Controls

For large tracts of land that are infested with gypsy moths, aerial applications of pesticides are used. These applications are generally coordinated through a local or state agency.

One product, Gypcheck, has been argued to be specific to gypsy moth removal only and bears no negative effects to both people's health and environment. This product contains the nucleopolyhedrosis virus which infects only gypsy moths.

Refernces

"Gypsy Moth—Unwelcome in Washington State!" Washington Dept. of Agriculture. Dec. 2008. 15 Jan. 2009. <http://agr.wa.gov/PlantsInsects/ InsectPests/GypsyMoth/default.htm#Factsheet>.

"Gypsy Moth in Virginia." Virginia Tech College of Agriculture and Life Sciences. Virginia Tech University. 15 Jan. 2009. <http://fubyss.ento.vt.edu/vagm/>.

"Gypsy Moth in Wisconsin." Wisconsin Dept. of Natural Resources. University of Wisconsin Extension. 15 Jan. 2009.
<http://www.uwex.edu/ ces/gypsymoth/>.

Liebhold, Sandy. "Gypsy Moth in North America." Northeastern Research Station. Oct. 2003. US Forest Service. 15 Jan. 2009. <http://www.fs.fed.us/ne/morgantown/4557/gmoth/>.

McManus, M., et. al. "Gypsy Moth." Forest Insect & Disease Leaflet 162. Oct. 1989. US Dept. of Agriculture Forest Service. 15 Jan. 2009. <http://www.na.fs.fed.us/SPFO/pubs/fidls/gypsymoth/gypsy.htm>.