Gypsy Moth ()
The gypsy moth,Lymantriadispar, is one of North America's most devastating forest pests. The species originally evolved inEurope and Asiaand has existed there for thousands of years. In either 1868 or 1869, the gypsy moth was accidentally introduced near Boston, MA byE. Leopold Trouvelot. About 10 years after this introduction, the first outbreaks began in Trouvelot's neighborhood and in 1890 the State and Federal Government began their attempts to eradicate the gypsy moth. These attempts ultimately failed and since that time, the range of gypsy moth has continued tospread. Every year,isolated populationsare discovered beyond the contiguous range of the gypsy moth but these populations areeradicatedor they disappear without intervention. It is inevitable that gypsy moth willcontinue to expand its range in the future.
The gypsy moth is known to feed on on the foliage of hundreds of species of plants in North America but its most common hosts are oaks and aspen. Gypsy moth hosts arelocated through most of the coterminous USbut the highest concentrations of host trees are in the southern Appalachian Mtns., the Ozark Mtns., and in the northern Lake States.
Gypsy moth populations are typically eruptive in North America; in any forest stand densities may fluctuate from near 1 egg mass per ha to over 1,000 per ha. When densities reach very high levels, trees may become completely defoliated. Several successive years ofdefoliation, along with contributions by other biotic and abiotic stress factors, may ultimately result intree mortality. In most northeastern forests, less than 20% of the trees in a forest will die but occasionally tree mortality may be very heavy.
Forest Effects
Despite over 100 years of presence in North America, researchers are still at a loss to explain and predict the extent of the changes in forest vegetation likely to take place through gypsy moth disturbance. A major concern is the potential loss of economically critical and ecologically dominant oak species (Quercus, spp.). Most studies of forest compositional changes with gypsy moth defoliation indicate that less susceptible species will dominate the forest, so in effect, forests may have fewer gypsy moth problems in the future.
Natural Enemies
A variety ofnatural agentsare known to kill gypsy moths in nature. These agents include over 20 insect parasitoids and predators that were introduced over the last 100 years from Asia and Europe.Small mammalsare perhaps the most important gypsy moth predator, especially at low population densities. Birds are also known to prey on gypsy moths but at least in North America this does not substantially affect populations. A nucleopolyhedrosisvirususually causes the collapse of outbreak populations and recently an entomopathogenicfungusspecies has caused considerable mortality of populations in North America.
Management:
Over the last 20 years, several millions of acres of forest land have been aerially sprayed with pesticides in order tosuppressoutbreak gypsy moth populations. Though some areas are treated by private companies under contract with land owners, most areas are sprayed under joint programs of state governments and the USDA Forest Service. Your localextension servicecan provide more detailed information about programs in your area.
The USDA, State and local governments also jointly participate in programs to locate anderadicatenew gypsy moth populations in currentlyuninfested areas. Most of these projects focus on populations of European origin, but recently severalAsianpopulations have been discovered and eradicated in the US and Canada.
In 1992, the USDA Forest Service began a pilot program to test the feasibility of slowing the spread (STS) of the gypsy moth in North America.STS pilot programscurrently exist in North Carolina, Virginia, West Virginia, and Michigan.
Management
Air temperatures of minus 20°F or colder during the winter will destroy exposed eggs. Unfortunately, numerous egg masses are deposited on rocks, near the base of tree trunks and these may be covered with an insulating blanket of snow. Freezing temperatures in early May, after hatch, may also kill many larvae.
Nonchemical- When the caterpillars are half-grown, many of them feed at night and crawl down the tree in the morning to seek shelter during the day. Tree trunks may be encircled with a 14-18 inch wide piece of burlap or similar material. Place it at about chest height and arrange it so it hangs apronlike around the tree trunk. Tie off the center of the burlap band with string and fold the top portion down over the string. This burlap apron provides a place under which larvae rest and can later be killed. The apron must be checked daily, and all “trapped” larvae and pupae should be destroyed. This technique works best in light to moderate infestations from late May through early July or until males begin to fly. This management method is usually effective enough to keep defoliation levels less than 50% of the tree’s crown. A few shade trees can be well protected with this method. Do not expect this technique to be effective on trees that are part of a heavily infested forest.
Male moths readily respond to the female’s sex pheromone. Males can be attracted to traps baited with a synthetic pheromone; however, such traps are not effective control measures. These traps do assist in monitoring an area for low level populations of this pest.
Biological Control- There are some native predators and parasitoids that attack life stages of this key pest. Several introduced species of fly and wasp parasitoids of the gypsy moth are established in Pennsylvania. Parasitoids and predators do not provide an immediate solution to an infestation. However, once a gypsy moth population collapses, their value is exhibited by helping maintain populations at low levels for extended periods of time. These parasitoids and predators appear to be contributing to stabilizing the gypsy moth population in several areas of the state. Native predators, such as birds, white-footed mice, and ground beetles assist in keeping this key pest at tolerable levels.
A naturally occurring virus called the “wilt” has resulted in massive mortality of caterpillars causing populations to collapse in areas of severe defoliation. Although the virus is always present, it seldom affects the larval stage until they are under stress, due to overcrowding or reduced food availability. In recent years during wet spring weather, the fungal insect pathogen, Entomophagamaimaiga, has also caused collapse of heavy infestations of this pest in many areas of Pennsylvania.
Chemical- Several insecticides are registered for effective management of this key pest. Applications should be made according to label directions after the majority of eggs have hatched during early to mid-May, when larvae are small. Be sure that small larvae have dispersed and they have begun to feed causing the characteristic shothole injury to host plant foliage. To maintain good plant health, applications should made before serious defoliation occurs.
Gypsy Moth(
It is thecaterpillarsthat do all the damage to trees. Gypsy moth caterpillars emerge in late April and feed on many types of trees until July. Caterpillars are easy to identify because they are large and hairy, with five pairs of blue tubercles (bumps) in front, and six pairs of red tubercles in back.
Gypsy moths' favorite trees andshrubsinclude: oaks, basswood, birch, Sweetgum, willows, and Witch Hazel. Some other trees they will eat include: hickories, maples, Black Cherry, American Elm, Sassafras, hornbeam, and Eastern White Pine.
Sometimes they eat other species too, but they never eat Eastern Redcedar, dogwoods, or ash trees. Because moths never eat them, these trees are helped by the moths which get rid of theircompetition. Caterpillars eat huge amounts of leaves, often stripping an entire tree, or even a whole section of forest, bare. This is called "defoliating.
When gypsy moths defoliate a tree, it cannot feed itself and it will die. Many of the trees European Gypsy Moth caterpillars eat, especially oaks, supply wildlife with food andshelter. Therefore, this insect is very dangerous for animals and even people. Scientists are trying to find ways to control gypsy moths.
Fortunately, gypsy moths have manypredators, including: birds, frogs, toads, skunks, raccoons, foxes, turtles, snakes, beetles, squirrels, chipmunks, bats, shrews, and lizards.
These caterpillars have an interesting behavior called "ballooning." They climb to the top of a tree and spin a silk thread which they let dangle. When the wind catches the thread, the caterpillar lets go and goes for a ride. Sometimes the wind carries the caterpillar far, but most of the time they land near the base of the tree.