Printer Friendly

Gypsy on the move.

A Landowner's-eye look at the latest inroads of this voracious forest pest and the newest tactics for controlling it.

Some months ago, walking through the house-adjacent portion of our hundred-acre forest "backyard," I realized anew how special May can be. The phoebes and towhees were beginning their morning songs, the wood thrush was down-ridge, and the ovenbird was starting his "teacher" chant. Close by, an unseen buck snorted a challenge to my presence, and I could see that a bear had been scratching for a meal in the fallen pine. A pileated woodpecker rummaging through the oaks drew my attention to the large, dark green leaves the trees were producting this year and reminded me of two previous springs when this was not the case.

I thought back to May 1989 when, after decades of on-site labor and planning, my husband and I finally realized our mid-life goal--retirement in a mountainside wilderness that borders Virginia's Shenandoah National Park. At long last, the structures were in place that would enable us to enjoy comfort as well as beauty, our goodbyes to fellow educators had been said, our suburban residence had been sold, and we were sure that rarely had luckier souls ventured into a forest home. But our happiness soon turned to shock.

Swinging into our lives on countless silky threads on that warm, early May day were what would soon become millions of minute black "things." We were experiencing our first major encounter with larvae of the gypsy moth --a pest that would create frustration, economic loss, allergic reactions, and periodic limits on enjoyment of our new outdoor Eden.

Following that jolting introduction, we learned--first-hand and through frantic phone calls to experts, community meetings, and perusal of scads of printed matter--about this insect that defoliated nearly 13 million acres of our nation's trees in a single season (1981) and threatens the forest environment we prize.

Many scientists believe that the gypsy moth (Lymantria dispar) evolved in the Far East and subsequently spread throughout the temperate regions of Eurasia, where a number of natural enemies keep the insect in balance. The gypsies were accidentally introduced into this country in Medford, Massachusetts, in 1869 when they escaped from a laboratory experiment in silkworm breeding. Since then, the insect has shown remarkable adaptability, mobility, and ability to increase at an accelerating rate.

Starting from its now-infamous origination point on Myrtle Street in Medford, the insect occurs today in more than half of the states in our nation and has caused untold timber loss as well as millions of dollars spent annually in control measures and research. In addition to economic factors, the aesthetic effects on forested areas are dramatic. Stands defoliated by July are commonplace, and the lack of acorns from those weakened trees poses a serious threat to the wildlife that depend on them.

In heavily infested areas such as the mountains where our home is located, the larvae and their frass (excrement) literally rain on outdoor activities from early May into July. When outside, it's impossible to enjoy liquid refreshment without covering the glass at all times, and even with that precaution you will likely find that somehow the insects have polluted it. Besides being extremely unpleasant, the foreign matter requires constant cleanup and diligence (falling on a slippery deck is one of the hazards).

The critter may also cause allergic reactions. My own response was similar to having a cold, but rashes occur in some individuals who contact the larvae hairs. On occasion the reaction can be caused merely through contact with laundry that has hung outside.

How does this small creature wreck such havoc in a two-month period? The tiny larvae emerge from buff-colored egg masses (containing up to 1,000 eggs each) at about the same time as the appearance of leaves in spring. Trailing silky threads, they begin a dispersal process to reach acceptable food sources. The leaves of oaks and aspen are the preferred food, but in laboratory experiments, the moths have eaten about 500 species of plants. The caterpillars feed, grow, and molt in a series of four- to 10-day stages five for males, six for females.

In late June or early July, eating ceases and for 10 to 14 days the fully developed larvae pupate in brown cases sometimes attached to previous resting sites. Upon emerging as an adult moth, the white female, which does not fly, releases a pheromone to attract the smaller but mobile brown male. The male, unlike most moths, is a daytime flier. After mating, the female deposits her eggs in a mass, thereby exhausting her stored energy, and dies soon after.

The eggs remain in the mass during the winter until the larvae emerge in the spring to start the reproductive cycle again. Since each female can produce hundreds of eggs, the stage is set for a geometric increase in the population the following year.

The trees left behind respond in several ways. If fewer than half the leaves are removed, most trees will experience lack of growth and perhaps loss of individual limbs. If the foliage is substantially stripped, the tree will drop the remainder and refoliate with a second, less productive crop of leaves. This process stresses the tree by using energy reserves needed for winter sustenance.

Trees weakened by defoliation are more susceptible to the ravages of disease organisms, other insects, and drought. Although many hardwoods can withstand one defoliation, other trees are more likely to die. Most mature hemlocks, for example, will be killed by a single defoliation--and gypsy moths will eat hemlocks if they are hungry enough and no hardwoods are available. This fate is unacceptable in our view, as our driveway is lined with several hundred large hemlocks.

Gypsy-moth populations advance to new areas, build up to outbreak numbers, and then wane for a number of years, only to repeat the cycle over and over. According to Jim Space, director of the U.S. Forest Service's forest pest management program, the moth is now entrenched from Canada south to North Carolina and from Ohio west to central Michigan, with isolated infestations in a number of other states.

The USDA Animal and Plant Health Inspection Service (APHIS) undertakes eradication of small outbreaks. For large moth populations, the Forest Service picks up 50 percent of the cost of cooperative projects, with state and local jurisdictions each covering 25 percent. Budget deficits may require landowners to be added to the cost-sharing mix. Although total eradication is improbable, those who work closely with this forest menace are optimistic about maintaining the populations at economically and socially tolerable levels using environmentally sound measures. Even as this adaptable, prolific creature carves out new territory every year, scientists in laboratories in many locations are learning more about its ways and developing technology to control the devastation it creates. Much of the research "is conducted by USDA labs and land-grant institutions," says Edward Connor, director of the University of Virginia's Blandy Experimental Farm.

A number of studies center around the naturally occurring nuclear polyhedrosis virus (NPV), which is specific to gypsy moths and causes epidemic disease and death in dense populations. The Forest Service has developed a formulation of the virus registered as "Gypchek"--that is in use as a pesticide. But problems exist. At Penn State, entomologist Jack Schultz and his colleagues are studying the relationship of tree chemistry and the virus. "We have confirmed that the more a tree is defoliated, the less effective is the virus," he says.

Also, ultraviolet rays kill NPV, and rain washes it from foliage. Connor's group has worked with a coating that holds the virus in place and reduces the ultraviolet effect. At the USDA Agricultural Research Service (ARS) lab in Beltsville, Maryland, research entomologist Martin Shapiro and his colleagues have developed a potent NPV strain and enhanced its effectiveness by including a laundry detergent additive.

Another project involves encouraging natural enemies of the moth introduced from Europe and Asia, where 50 to 100 species of natural enemies exist, according to Roger Fuester of the ARS Beneficial Insects Introduction Research Laboratory.

Boyce Thompson Institute research associate Ann Hajek has been studying the effects of the Japanese gypsy-moth fungus Entomophaga maimaiga. "We placed the fungus in 34 sites in areas recently invaded by the gypsy moth," she says. "Some sites experienced a 75 percent mortality due to the fungus alone."

As my husband and I watched winter turn to spring and back to winter in 1989 and 1990, we learned that we were not helpless against this forest ravager. We contacted local and federal officials for information, and through the assistance of Stephanie Springer, our county's dedicated gypsy-moth coordinator, we became involved with the Appalachian Integrated Pst Management (AIPM) program.

AIPM, a five-year project initiated by Congress in 1987, is funded through the Forest Service and operates in 38 Virginia and West Virginia counties. According to Gary McAninch, AIPM coordinator for Virginia, the objectives of the program are "to demonstrate that we can slow the spread and reduce the impact of the gypsy moth, develop a model for use in other parts of the country . . . and develop a computerized information system for use in many areas."

AIPM employs a variety of intervention techniques, including aerial application of viral, bacterial, and chemical pesticides in high-density moth populations, and, in low-level populations, release of sterile life stages, moth trapping, and mating disruption through dispersal of commercially produced sex attractants.

Not everyone agrees with gypsy-moth intervention. At Shenandoah National Park, management is limited to high-priority areas. In 1991, for example, 1,160 acres were treated in a "priority suppression zone" along Skyline Drive, in campgrounds and other "people" areas, and in sections with unique natural features, while approximately 40,000 acres of the park were left to be defoliated.

Another controversial issue is the use of pesticides. In most cases, the decision to use chemicals will be influenced by the number and kind of trees affected, the degree of defoliation, proximity of the property to a heavily infested area, and a prediction of severe infestation from eggmass counts the previous fall. In the past, insecticides like DDT have been used that have harmful environmental impacts, but those used today are more limited in their effects.

Based on advice we were given, we thinned our oak forest to increase the vigor of the remaining stand. In the midst of a severe outbreak in 1990, our forest was included in the AIPM aerial spraying plan. While we cheered from our deck, Bacillus thuringiensis (Bt), a bacterium that causes infection and starvation when eaten by caterpillars, was sprayed along our creek. Elsewhere on our ridge, the even more effective diflubenzeron, was applied.

Prior to the spraying, larvae and frass covered our home, decks, ornamental shrubs, trees, garden, and even us whenever we ventured outside. Two weeks after the spraying, in the middle of a rainy spell, the caterpillars began to disappear. The difference was miraculous. We cleaned up carcasses and crossed our fingers.

When May 1991 came, we watched anxiously for signs of the dreaded caterpillars. But thanks to the cooperative efforts of many individuals, groups, and agencies, the insect did not materialize in damaging quantities. Once again, we are a happy human family in the midst of a forest home where deer, raccoons, bears, squirrels, and birds have resumed normal activities--and where the gypsy moth, for this year at least, was stopped in its tracks. AF

1967 52,373 0
1968 80,123 60
1969 255,829 830
1970 972,833 10,500
1971 1,945,224 598,200
1972 1,369,130 404,060
1973 1,773,846 856,710
1974 750,905 479,590
1975 464,451 317,880
1976 865,442 732,310
1977 1,596,019 1,296,550
1978 1,259,246 452,892
1979 643,609 8,552
1980 5,005,389 440,500
1981 12,872,725 2,527,753
1982 8,171,191 2,351,317
1983 2,383,368 1,360,824
1984 992,655 450,642
1985 1,709,300 581,113
1986 2,412,900 987,819
1987 1,329,653 880,335
1988 719,302 312,092
1989 2,995,559 1,506,790
1990 7,374,816 4,357,700
1991 4,000,000 est. 1,230,000

This listing of acres infested from 1967 through 1991 clearly shows the ebb and flow of gypsy moth outbreaks, both in the U.S. overall and in Pennsylvania, where more defoliation has occurred than in any other state.


An invasion of the voracious Asian gypsy moth has officials in tile Pacific Northwest scrambling. Entomologists theorize that the Asian moth mall have hitchhiked here aboard ships. Stowaways that have jumped ship in U.S. ports, if left unchecked, could decimate the region's deciduous and coniferous forests as well as homeowners, yards.

Unlike the North American or European gypsy moth, which prefers deciduous trees and is capable of flight only if it's a male, the Asian moth also has a taste for conifers and both of its sexes can fly. Healthy deciduous trees can recover from defoliation, hut conifers cannot survive any significant loss of needles.

"On the East Coast, the North American gypsy moth with its flightless female took 130 years to move from Boston to western Pennsylvania," says Mary Beth Lang, information officer for the Washington State Department of Agriculture. "Here, if the Asian strain can fly 20 miles, it's not going to take that long to move. The Asian gypsy's a much bigger problem to contain if it should become established. "

U.S. Department of Agriculture entomologists have confirmed at least three captures of the Asian strain, Lymantria dispar, in Washington and another in Oregon. The pest has also been found in British Columbia, which will begin eradication this spring. So far, most of the finds are near ports.

In Asia, the moth is at the peak of its population cycle, according to Lang. In the Russian port of Vladivostok, the moths are attracted to lights on docks when ships are being loaded.

On board ship, the females lay eggs that hatch in transit. The larvae are blown off when the ships arrive in U.S. ports. Also, unhatched eggs may be overlooked during inspection and move off the ships to develop into adults on U.S. soil. It appears that moths moved off ships in Tacoma, Washington, and one was trapped as far as 20 miles away.

"In September," Lang says, "we did some inspections and did find a ship with viable egg masses on it and also one with empty egg masses. Both had been in Puget Sound ports during last spring. We are seeing a lot of signs pointing to the need to take action now. "

Officials with the U.S. Department of Agriculture, the U.S. Forest Service, and state agriculture departments recently began developing a plan for detecting and eradicating Asian gypsy moths. "There are still issues that have to be decided and resolved," says Robert Nave, a Department of Agriculture official. "It's going to depend on plans yet to be made, as well as funding. "

A plan is expected to be in place sometime this spring.

Doris Pond is a retired teacher who monitors the gypsy from her home in Stanley, Virginia.
COPYRIGHT 1992 American Forests
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:includes related article; gypsy moth
Author:Boyd, Vicky
Publication:American Forests
Date:Mar 1, 1992
Previous Article:New hope for forest communities.
Next Article:Report from Lucy's Woods.

Related Articles
Taking AIPM at the gypsy moth.
How to minimize moth mayhem.
Saving forests the natural way.
Gypsies and beetles and frass - oh, my!
Fungus routs gypsy moth outbreak.
Caterpillar bodies not built for speed.
Humans blamed for gypsy moth spread.
Squelching gypsy moths: what's hot and what's not in the arsenal against leaf eaters.
Fly may be depleting U.S. giant silk moths.
Insecticide gets help from gut bacteria.

Terms of use | Copyright © 2017 Farlex, Inc. | Feedback | For webmasters