Special to the OBSERVER
The Gypsy Moth was originally brought from Europe by Leopold Trouvelot to the United States in 1869 in an effort to improve the silkworm industry. Several cases of the larvae were overturned in a windstorm near Boston and the larvae were released into the forests of Massachusetts. Within 20 years the species caused serious harm to those forests. Since that time millions of acres of forest lands have been defoliated in the northeast. In 1991 and 1993 ships from Russia and Germany introduced the species to the northwest and the Carolinas.
Gypsy moth caterpillar.
The picture shows a female adult moth laying eggs on tree bark. Notice the darker color under her wings, this is the egg sac. The caterpillars are usually black and quite hairy with two double rows of spots from front to back. The first five pair of spots are blue and the second six pair are orange to red. The female adult is white and black, and the male is grey and black.
The larval (caterpillar) stage is the one that does all of the damage to the trees by eating the leaves until the tree is completely defoliated. A vigorous hardwood tree can survive this damage but cannot survive two or more defoliations. Oak trees are their favorite, however they also like the leaves of apple, basswood, cherry, elm, hemlock and maple. In a severe outbreak of Gypsy moths, any vegetation is at risk.
The caterpillars disperse over long distances in various ways; the main two ways include hitch-hiking a ride on cars and trucks in the egg stage, while the hairs on the caterpillar stage contain air pockets that allow them to be blown on the winds for many miles a day.
There are a number of ways you can control Gypsy moths around your home that do not require the use of pesticides or insecticides. Use a common garden hose with a spray attachment and spray your trees with insecticidal soap. This will kill a great many of the caterpillars you have on your trees very quickly. Just plain water can kill them if you have good water pressure.
An effective way to eliminate them is the use of barrier bands; that wrap around the trunk of your trees. The bands can be purchased at local nurseries or department stores that have garden centers. The bands are coated with a sticky substance that traps the caterpillars when they try to cross over them; simply scrape them off when the trap is covered. You may have to replace the bands if they become worn. You can do the same thing with burlap strips. You just tie some twine around the trees and drape the burlap over the twine. The caterpillars hide under the burlap when they come down from the trees. Just scrape them into a jar of soapy water.
You might be wondering why we are talking about the caterpillar stage when they are in the adult moth stage right now; one of the best control methods is done in late September. Find the egg sacs where the adult moth has laid them on their favorite trees and scrape the sacs off and destroy them. If you don't, in the spring the eggs will hatch and there will be around five hundred caterpillars in each egg sac, so destroying them this fall is much easier then dealing with them in their larval stage next year!
Rick Martin: Cornell Cooperative Extension Master Gardener