In the late 1860?s a misguided French artist and scientist named Etienne Leopold Trouvelot returned from France to his American home in Medford Massachusetts with egg masses of the gypsy moth. The reasons for transporting the alien insect remain shrouded in history but the wily gypsy moth managed to escape the confines of Trouvelot?s laboratory and infested oak trees behind his home. Trouvelot notified local officials of this accident but to no avail. No early steps were taken to eliminate this pest and it established in the hardwood forests of New England. In the intervening 140 years gypsy moth has become the most significant pest of hardwood trees like oak, beech, and hickory in the eastern United States.
During years of peak activity in the early 1980's the gypsy moth was responsible for defoliating more than 12 million acres of forest and shade trees nationwide. The gypsies moved south and west from New England spreading their wave of destruction. By the early 1990's, gypsy moth was well established in our area and more than 130 thousand acres of trees were defoliated in Maryland in 1990. To help protect our urban and natural forests from this pest, state governments cooperate with their federal partner, the US Forest Service, to track the movement and abundance of gypsy moths. These agencies also work together to slow the spread of this pest in its relentless march. Within the generally infested area of the gypsy's range, which includes Maryland, Virginia, and the District of Columbia, government agencies supervise and coordinate large-scale efforts to reduce gypsy moths when populations are high and on the rise. In our area these programs include aerial sprays of insecticides. The high water mark for spray programs in Maryland was 1990 when more than 200 thousand acres were treated. Last year was also a record year for the gypsy moth in Maryland.
For the first time since 1979 not a single acre of forested land was treated by the state. One of the key factors holding the gypsy moth at bay is a fascinating fungal disease called Entomophaga maimaiga. This fungus is a native of Asia and was released in New England. In 1989 an epizootic of Entomophaga decimated gypsy moth populations in seven Northeastern states. It has since spread throughout much of the range of gypsy moth where it maintains the gypsy at innocuous levels in most years. However, this year the gypsy has returned. In my favorite gypsy moth patch in College Park this week, I observed tiny gypsy moth larvae hatching from buff colored egg masses left on the tree by fertile female moths last summer. These hairy black caterpillars were munching oak leaves with their relatives the forest tent caterpillars. We met a close relative of the forest tent caterpillar called the eastern tent caterpillar in the March 20 episode of bug of the week: Time for tents - Eastern tent caterpillar, Malacosoma americanum. Please click on the link to learn more about Eastern tent caterpillar.
Unlike last year, gypsy moth populations are on the rise and the state of Maryland will treat more than 25,000 acres of forested land to suppress this pest. The counties included in the 2006 Gypsy Moth suppression program are: Allegany, Carroll, Cecil, Frederick, Garrett, Harford, Howard, and Washington. To view the areas to be treated in these counties just click on the name. Exactly why gypsy moths are on the upswing in our area again, no one knows for sure. Perhaps, the drought that began last summer and continues into this spring reduced the ability of the fungus, Entomophaga, to attack and kill gypsy moth caterpillars. Scientists with the US Forest Service have discovered an intriguing pattern of waxing and waning in gypsy moth populations in cycles or 5 to 10 years for several decades. What drives these cycles is a biological riddle yet to be definitively resolved. Whatever the reason, we know for certain that the gypsies are back. Go out and have a look at your oak trees. Small holes in the leaves could be an indication the gypsies or forest tent caterpillars have set up camp at your home.
We thank Robert Tichenor, Forest Pest Management, Maryland Department of Agriculture for a lively and informative discussion of the gypsy moth status in the state. For more information on the history, biology, and management of the gypsy moth, please visit the following web sites.