Should I be worried about the fuzzy caterpillars that are defoliating my oak?

Over the past month or so, the Infoline has gotten many questions about one particular group of hairy caterpillars, the tussocks. Not only are they feeding heavily on many different types of woody, deciduous plants, but in the case of the hickory tussock moth they are also giving some people a painful, itchy rash.

The bodies of tussock caterpillars are coated with dense hairs. These hairs are hollow and can puncture the skin when the caterpillars are handled or disturbed, causing allergic reactions in sensitive individuals. These hairs, combined with striking color patterns, serve as effective deterrents and defenses against predation. Hickory tussock moth caterpillars are white with prominent black tufts of hair along their bodies. Very few bird species are willing to eat them. Rashes from most tussock caterpillars don’t last very long, except in the case of the hickory tussock moth caterpillar, which can cause a severe reaction. Although not everyone is allergic, it’s always best to avoid touching any tussock caterpillars with bare skin.

In addition to causing aggravating rashes, tussock caterpillars are also capable of consuming large amounts of plant material in short order. Most species conspicuously feed during the daylight hours on the upper surfaces of leaves, and many species will feed on just about any woody plant. Hickory tussock moth caterpillars prefer hickory, American hornbeam, ash, elm, and oak, but will feed on numerous other plants too. Fortunately, because most of this feeding occurs in the late summer and early fall, it does little to harm overall plant health since trees and shrubs are preparing to drop their leaves in just a few short weeks anyway.