The gypsy moth was actually brought to the United States in 1869 in an attempt to start a silkworm industry. The gypsy moth is an example of an experiment gone horribly wrong. Needless to say, the silkworm industry experiment failed with the moth escaping soon afterwards to become, over the past century, a major pest in the northeastern United States and southeastern Canada.
The insect larvae, which are caterpillars, emerge from their eggs beginning in early spring and continuing through mid-May to start the devastating tree damage. Devouring mostly at night, the caterpillars crawl from leaf to leaf eating all the way. And they are not fussy eaters. During the daylight hours, larvae generally seek shade from the sun. But even during the day, if the investation is heavy, the caterpillars have been known to eat away the leaves continually. As the gypsy moth larvae grows, it moults - five moults for males and six for females. Feeding mostly occurs in the period between each moult which is known as the instar stage. Every time the caterpillar moults becoming bigger, its appetite also becomes larger, as might be expected. This feeding frenzy continues until mid-June or early July. Then the caterpillar enters the pupal stage emerging, finally, as a moth. Both male and female moths exist only to reproduce once with the male moths flying to find the females who are too heavy to fly. Depending on the location, after the females lay their eggs from July to September, moths of both sexes die.
Unfortunately, the devastation is not limited to just a few trees. The gypsy moth caterpillar has a preference for the leaves of deciduous hardwood trees such as maple, elm, and their favorite, oak. However, gypsy moths can also feed on apple, alder, birch, poplar and willow trees. And as the caterpillar grows, it will attack evergreens like pines and spruces. Gypsy moths appear to dislike ashes, sycamores, butternuts, black walnuts, dogwoods and balsams. But during heavy infestations, the competition for food will drive the caterpillar to attack almost any tree or shrub around.
The tree damage can range from light to almost complete defoliation depending, of course, on the degree of infestation. Most deciduous trees can survive a moderate degree of defoliation. Many trees can even survive one complete defoliation by the gypsy moth caterpillar. But if the tree continues every year to be attacked, it can fatally weaken the tree leaving it exposed for further damage from other devouring insects and vulnerable to disease.
