News Release - (SCFC HQ, Columbia) Since late April, homeowners have begun to notice the caterpillars of the common oak moth, Phoberia atomaris. South Carolina Forestry Commission staff say this caterpillar has been found feeding primarily on post oaks and other white oaks in the Anderson, Chapin, and Irmo areas, but they could show up anywhere in the state.
"This is a native pest which leaves a yucky calling card," said Laurie Reid, insect and disease specialist with the Forestry Commission. "At one residence, the caterpillars were found wandering from the host tree on to the porch and into the garage, leaving a long trail of rusty colored vomit."
The common oak moth occurs sporadically through the eastern United States, from Massachusetts to Florida, and west to Texas and Kansas.
There is only one generation (egg, larva, pupa, and adult) per year; the ground-dwelling pupa is its "overwintering" stage. Early each spring just before buds break, adults emerge from the pupa and mate. Female moths lay eggs and the caterpillars binge on the newly emerging leaves.
Identification
The caterpillars are variable in color: they are smooth, brown mottled with white, tan, and black; the prolegs on the third abdominal segment are half the size of the prolegs on the fourth abdominal segment, which are smaller than the prolegs of the fifth and sixth abdominal segment. On the seventh abdominal segment there often is a conspicuous white spot above the spiracle (holes in the bug through which it breathes).
Damage
The tattered foliage or completely defoliated trees, caterpillar frass (waste material), and wandering caterpillars can be a nuisance to homeowners, the SCFC's Reid warns.
"However, there is no long-term affect for most healthy trees and most trees will put out another flush of leaves," she added.
Typically, trees which have been defoliated by this oak moth caterpillar for many years in a row and which happen to be stressed by other factors may experience some damage (such as limb loss) or, in the worst cases, tree mortality.
Natural enemies usually keep the caterpillar numbers in check and, according to Reid, the experience won't last too long anyway. "Luckily for homeowners, in the next few weeks the caterpillars will form an underground pupa where they will remain for the rest of the summer and through the winter."
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