Fortunately, nature is now helping with their control: A natural fungus and a virus have kept their numbers in check for the last 10 years or so and aerial spray is not needed in as many areas in Virginia as during the highest outbreak years.
The baby caterpillars emerge from their egg masses usually at the end of April to early May in the Shenandoah Valley and Piedmont. They go through five instars, eating more vegetation as they get larger and become adults. The caterpillars are unmistakable with two rows of red and blue dots and long dark hairs. Pupation occurs in June or July, depending on elevation, and by then, the damage to trees and shrubs can be significant if populations are high. The adults moths breed - the female moth is quite large, averaging about one and a half in length - and lays her signature tan egg mass on tree trunks, the underside of limbs or the sides of structures. The larvae overwinter, emerging again the following spring.
It is believed that a new outbreak occurred in Oregon when an automobile part was sold on Ebay: the vehicle from which the part was taken was parked under a tree in the East and an gypsy moth had laid an egg mass on the part. It was installed on a vehicle in Oregon, the caterpillars hatched and a new infestation occurred. Each egg mass can contain up to 500 larvae.
It is difficult to predict when gypsy moth populations will once again increase in Virginia but hopefully we will not experience the substantial tree mortality that previous outbreaks have caused.