Small bug, huge threat

Image courtesy of
Image courtesy of

During the summer when the trees are covered in leaves, it seems that only the following season will endanger the trees. However, this is not the case. During late spring and early summer, starting around mid-May, gypsy moths hatch from their eggs and devour millions of acres of trees. The gypsy moth caterpillars eat over three hundred species of trees and shrubs, but prefer oak trees. 

In 1869, the gypsy moth was introduced in Medford, Massachusetts, by Leopold Trouvelot, a French astronomer. Trouvelot wanted to develop a species of silk moth that was resistant to disease, in an effort to strengthen the silk industry. However, a few of the moths escaped into the wild and bred. Though sprays to keep the moths away are sometimes released, the gypsy moths still devastate forests around the nation. The United States Department of Agriculture and the Animal and Plant Health Inspection Service predicts that there will be approximately 685 million acres infested by gypsy moths by the year 2010. 

Because deciduous trees naturally lose their leaves, it may seem as if the gypsy moths are bringing no harm to the trees by eating the leaves. However, the gypsy moth caterpillars rapidly rid the tree of its leaves, forcing the tree to use its reserves of water to grow new leaves. By straining to replenish itself by using its energy and water reserves, the tree suffers weakened natural defenses. These defenses are needed for the upcoming cold seasons, and if it is not protected well enough, the tree may die.  

Gypsy moths typically defoliate over one million acres of forest in North America each year, but in 1981, the gypsy moths set a record. The larvae had defoliated 12.9 million acres of trees in one year – an area larger than Rhode Island, Connecticut and Massachusetts combined. Some adult gypsy moths even lay their eggs on transportation vehicles, such as cars, trucks and boats. Then the eggs hatch and are introduced in a new area, starting the infestation in a new location. In the wooded suburbs, gypsy moth larvae are commonly found crawling everywhere: on walls, in the street, on outdoor furniture, and even inside homes. When the infestation is at a very high rate, one can sometimes even hear the larvae chewing, and will find droppings of the caterpillars wherever the larvae have been. 

Loss of foliage on the trees affects other life as well. According to the Wisconsin Department of Natural Resources, “trees weakened [by gypsy moths]…stop making nuts, sometimes for years, and wildlife [loses] a food source that they depend on. While the trees are bare, predators can easily find nests and songbirds may lose their young. Lack of shade from the tree makes water temperatures warmer, which lowers the amount of oxygen in the water for aquatic plants and animals. A dense canopy of leaves also buffers the violence of summer storms. When that protection is lost, rainwater erodes the soil and lowers water quality in streams. Fish and other aquatic animals can be stressed during this period before trees [grow new leaves].”

Nearly everyone knows that trees are needed for human survival, but it is not often that people think of a mere moth as one of the biggest threats to one of our most-needed resources. Gypsy moths may be frequently seen this season, but as time goes on, we may be seeing them even more.