Plant Industry - Plant Protection Section
Identifying the gypsy moth
The two gypsy moth lifestages that are easiest to identify are the caterpillar and egg mass. Unfortunately, pupae and moths can be easily confused with other species.
The egg mass is tan or buff colored and hairy. It is typically oval in shape, about the size of a quarter. Females tend to lay their eggs in sheltered places such as on the underside of a tree limb or in tree bark furrows, although they can be laid anywhere a female is able to crawl (lawn ornaments, play equipment, car wheels, house siding, etc). In North Carolina, egg masses are present from August through April, though the remnants of egg masses linger year-round.
The caterpillars are the most colorful (and damaging) stage. After hatching, they are very small (roughly 1/16 inch in length); however, just prior to the onset of pupation they reach their largest size, 1.5 to 2.5 inches in length. Hatch is not a single event – it can occur over a time period as long as a month. Caterpillars have a bright yellow head capsule, and five pairs of blue dots followed by six pairs of red dots on its back. It is very hairy. Caterpillars may be found from late March to late May in North Carolina.
Unlike some of its look-alikes, the gypsy moth weaves no webs.
Eastern tent caterpillar larvae look similar in size and coloring to gypsy moth larvae. However, eastern tent caterpillars, as the name suggests, weave tents in tree branch crotches, where they live gregariously. They feed on most members of the rose family, most prominently black cherry, but also apples and hawthorns. While their tents are unsightly and a completely defoliated tree is not very attractive, they almost always do not do significant damage to the trees. They only have one generation per year, and after the caterpillars have finished feeding (usually by May or June), the trees will leaf out again.
Because the defoliation comes so early in the growing season, eastern tent caterpillar does not usually cause permanent damage. It is more of a nuisance. However, if you would like further information on this insect, please refer to this INFORMATION SHEET from the Kentucky Cooperative Extension.
Fall webworm larvae are also similar in size and coloring to gypsy moth larvae. They also weave tents, however, these tents are usually located at the ends of branches. Like eastern tent caterpillars, the result of an infestation of fall webworm is ugly, but they almost always do not do significant damage to the trees. They also have one generation per year. Additional defoliation from these insects will not happen until next fall. Defoliation first appears around August. Since the defoliation happens only toward the end of the growing season, the majority of the leaves’ potential photosynthesis for the year has already occurred.
There are several options for control of fall webworm. The most obvious is to clip and burn (or otherwise destroy) branches below the tents. If necessary, there are also several different insecticides registered for fall webworm. Please refer to this INFORMATION SHEET from Penn State Cooperative Extension.
Fall cankerworm larvae are harder to spot, but distinct from gypsy moth larvae. They have an inchworm-like habit and defoliate oaks, maples, elms, hickories, ashes, and cherry. Unlike fall webworm and eastern tent caterpillar, it can be damaging. Please refer to this INFORMATION SHEET from the Penn State Cooperative Extension.
If you suspect that you have a gypsy moth infestation, please call us immediately. However, if you are sure of an infestation of any of these three pests, please contact your local Cooperative Extension office. (http://www.ces.ncsu.edu/index.php?page=countycenters)