Red Oak Borer

The red oak borer, Enaphalodes rufulus, is a native pest of oaks (Quercus) throughout the eastern United States. While infestations usually do not lead to tree mortality, the wood is often severely damaged, resulting in degraded timber and a loss of lumber value (US Forest Service 1989).

Adult red oak borers are mostly nocturnal and are active in mid to late summer. They are large light-brown longhorned beetles, 1 to 1 ¼ inches in length (Solomon 1995). Female antennae are about as long as the body and male antennae are up to twice as long as the body. Larvae are thick and white with dark mandibles.

Red oak borers have a two-year life cycle (Donley and Acciavatti 1980). Adults emerge in mid-summer to mate and lay eggs. Eggs are laid in bark depressions, under lichen patches, or under vines on the bark’s surface. The newly hatched larvae burrow under the bark to feed upon the vascular tissue. Larvae over-winter within the tree. During the next season the larvae begin feeding upon the wood of trees, creating large mines. Pupation occurs early in the following season. New adults emerge in mid-summer through large exit holes. Throughout the southern Appalachians, adult emergence is synchronized to occur in odd-number years (Donley and Acciavatti 1980). Evidence of infestations include fine frass, discolored bark patches, oozing sap, and exit holes (Solomon 1995).

Red oak borer infest many different species of oaks in the eastern United States. Red oaks tend to be more susceptible than white oaks with the most common hosts being northern red oak (Q. rubra), black oak (Q. velutina), and scarlet oak (Q. coccinea); all of which are common throughout the southern Appalachians (Solomon 1995). Woodpeckers feed heavily upon larvae, often reducing larval numbers by as much as 40% (Donley and Acciavatti 1980).

Since red oak borer infestations are a natural part of the ecosystem and rarely lead to tree mortality, the ecological damage to the southern Appalachians is minimal. However, the large mines created within the wood of many oaks do affect the economic value greatly.