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More gypsy moth mayhem?
BY CHARLES GARRATT • STAFF WRITER
 | | A gypsy moth caterpillar munches away on a leaf. During periods of major infestations, the moths can defoliate trees. In 2000, more 18,000 acres of woodland were defoliated in Bath County. The caterpillars have done their work for this year and are turning into moths which lay eggs and then die. (Photo by USDA Forest Service, Forestry archives, bugwood.org) |
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WARM SPRINGS - State forester John Wright told the Bath County board of supervisors last week the gypsy moth population may experience another devastating explosion next year in Bath or Highland counties.
"What we have learned," he said Monday, "is that once you have gypsy moths, you always have them." The population is cyclic, he explained.
There may be little sign of gypsy moths for a number of years and then, boom: areas of defoliation. Wright said people should be on the look-out for small areas of defoliation and egg masses now and in coming weeks.
Bath County was hit hard in 2000 when 18,244 acres were defoliated, placing the county first among Virginia counties impacted that year. A number of factors combined to reduce the population in following years, said Wright.
 | | Everyone should be on the lookout for gypsy moth egg masses like these. Female moths will lay eggs under tarps, on structures, trees, campers, just about anywhere. Scrape the egg masses into a container of bleach, ammonia or kerosene to kill the eggs. (Photo by Pennsylvania Dept. of Conservation and Natural Resources, Bugwood.org) |
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The moths are "right here in Bath County, we just don't know it yet," Wright said. "The key is finding egg masses right now."
With hundreds of square miles of forest land in Bath and Highland, Wright cannot check all the places where moth populations may be building.
Some nearby counties have experienced significant defoliations this year. The Peters Mountain and Salt Pond Mountain areas near Mountain Lake in Giles County have many large areas of defoliation, according to Andy Roberts, entomologist at VA Tech.
Roberts said it is difficult to monitor a growing moth population, even from the air. The state maps areas of defoliation each year using ground and aerial surveys, but only checks areas where defoliation is reported.
 | | Gypsy moth pupae cover this tree near Mountain Lake in Giles County on Monday. A female adult is laying eggs in the right center of the photo while other egg masses are scattered on the bark. The pupae will mature into adult moths in the coming days. (Photo courtesy Andy Roberts, VA Tech) |
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The Virginia Department of Agriculture has a cost-share program to help landowners pay to spray woodlots infested with gypsy moths. The program requires the county to be well-organized, Roberts said. Last week, at the urging of Wright, Bath supervisors authorized county administrator Bonnie Johnson to look for a coordinator for the program.
To receive approval to spray and certify lands qualifying for spraying takes several months, Wright said. The coordinator must be in place by November for the county to be prepared for spraying next spring.
The spray program is only for private landowners and stateowned forest land, Wright added. The federal government handles forest service and other government property, he told supervisors.
 | | State forester John Wright explained the life cycle of the gypsy moth to supervisors last week. The specimens mounted in this frame illustrate all but the larvae or caterpillar stage of the forest pest. It is only the caterpillar that damages trees while it feeds. Bath and Highland may face another major out break next year according to Wright. (Recorder photo by Charles Garratt) |
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Two different agents are used to spray in this area and both have potential impacts on other species, said Roberts. BT, Bacillus thuringiensis, is a naturally occurring soil bacteria toxic only to moth and butterfly larvae.
BT is the most commonly applied aerial insecticide against the gypsy moth and is available to homeowners without requiring pesticide applicator certification.
An insect growth regulator, Dimilin®, interferes with the caterpillars' ability to develop normally. It is restricted to licensed pest control applicators. Roberts said Dimilin® has the potential for wider damage to other species, especially aquatics, than BT.
However, the survey and public hearing process address issues of safety and populations of nontarget species tend to recover quickly, said Roberts.
The spray program will be available to landowners if the number of egg masses per acre is above a certain threshold. The program will split the spray cost 50/50 with the landowner.
Individual egg masses may be scraped from trees and other objects into a container of bleach, ammonia or kerosene to kill them, according to the U.S. Department of Agriculture. The process is tedious but may be effective in protecting individual trees in a landscape planting.
The gypsy moth does not actually kill the tree, said Roberts. A healthy tree can withstand one or two defoliations, he noted. But if the tree is already stressed by drought, defoliation may kill it.
Also, on the rocky shallow soils in the mountains, a tree may not have enough nutrients available to recover from defoliation, said Roberts. And a weakened tree is more susceptible to disease and may be killed by a more common disease or insect.
Wright is concerned for older trees in the forests and woodlots which may have slow growth and are already weakened. Last week, he pointed out a number of older oak trees along U.S. 220 he suspects could be killed by a single defoliation.
Gypsy moths were first detected in Bath and Highland counties in 1986, said Roberts. For more than 10 years, traps were placed around the counties to monitor the spread. Once the moth became established in the two counties, trapping moved south and west to monitor the spread.
Only the larvae or caterpillars damage trees. The gypsy moth prefers oak, aspen, willow, birch, apple and basswood. But during major infestations when food is short, the older caterpillars will feast on hickory, maple, elm and many conifers.
Gypsy moths are sometimes confused with varieties of tent caterpillars which build silken "tents" in trees. The gypsy moth caterpillar does not make a tent.
The young caterpillar will use a strand of silk to travel after it hatches. The tiny caterpillar climbs to the top of a tree, spins a thread of silk and catches a ride on the wind, traveling up to hundreds of yards, said Roberts. The process is called ballooning and is also used by spiders.
After the caterpillars feed for about six weeks, they form a hard shell covering called a pupae and change into adult gypsy moths. The process takes about 10 days. The adult moths hatch and live only a few days. They do not feed.
The female moth does not fly but may crawl a short distance to find a place to lay eggs. The female releases a scent, called a pheromone, to attract flying males. The pheromone is used in traps to attract and capture the male moths.
The egg masses may contain hundreds of eggs and live through the winter. The masses are covered with hairs from the females body to help protect them. The eggs hatch in the spring and the tiny young caterpillars set off to feed.
The "gypsy" name implies the moths like to travel. Roberts explains the moths do not spread by flying or travel of the young caterpillars. Rather, the adult female caterpillar will search for a place to pupate. When populations are high, the caterpillar may end up falling on or crawling to campers, vehicles, structures and other objects.
When the female moth emerges, eggs are then laid on the object or vehicle which then can transport eggs to a new location.
Transportation of fire wood and infested forest products such as timber also spreads the moth.
During the last infestation in Bath, people reported being able to hear the caterpillar munching in the trees and droppings falling almost like rain in the late spring.
A spray program combined with a natural virus and an introduced fungus reduced the populations in recent years, said Wright. The fungus seems to be most effective during wet springs.
If conditions are right, the population can explode in a short time, defoliating anything from a few acres to thousands.
The gypsy moth is a native of Europe and was accidentally released in the U.S. in the late 1800s near Boston, Massachusetts. The pest has spread steadily southwest through the Appalachian hardwood forest.
The first defoliation in Virginia occurred in 1984. As of 2001, 4.5 million acres had been defoliated in the state, according to the Virginia Extension service. The leading edge of the spread is now in southwest Virginia, said Roberts.
For more information visit: gypsymoth.ento.vt.edu/vagm/ index.html on the web or contact John Wright at (540) 839-2260.
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