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Longhorned Beetles/Roundheaded Borers



Authors as Published

Eric R. Day, Manager, Insect Identification Lab, Virginia Tech






Larvae up to 3 1/4 inches (80mm) or more.


Adult longhorned beetles are medium to large cylindrical beetles, usually brown, reddish brown, or black in color. They are sometimes mottled or banded with white or gray. Larvae (roundheaded borers) are brown, reddish brown, or black. They are sometimes mottled or banded with white or gray.


Adults are called longhorned beetles because of their long and distinctive 11-segmented antennae, often longer than the beetle's body. The thorax and wing covers on some species bear small, stout spines. Roundheaded borers (larvae) are elongate, cylindrical, and have large gnawing mandibles. The name roundheaded borer refers to the enlarged thorax directly behind the head.




Most of the hundreds of species of roundheaded borers are found in weakened, dying, and dead trees. In addition, they feed on felled trees, stumps, and cut firewood. A number of species can also be found on healthy trees. Roundheaded borers feed under the bark and in the sapwood of trees. Adults often emerge from firewood that is brought into the house and may cause concern. They will not infest structural wood and are a nuisance only. Life Cycle: Many species emerge in the spring, while others emerge at other times during the growing season. Some may emerge over a two- to three-month period. Some species do not feed as adults, but others may spend some time feeding at flowers. Adults lay their eggs on weakened and damaged parts of the tree. The larvae bore into the tree, feeding under the bark at first, and later bore into the heartwood. They may take one to several years to mature before they pupate inside the tree just under the bark.

Type of Damage

Roundheaded borers feed under the bark and in the sapwood of trees. They bore long holes as they feed and weaken and destroy the wood. Infested trees are often rendered unusable for commercial purposes. A number of species in this family attack live, healthy trees, including locust borer, dogwood twig borer, azalea stem borer, sugar maple borer, red oak borer, white oak borer, and the round-headed apple tree borer. The pine sawyer feeds on weakened and stressed live trees.

Longhorned beetles do very little damage to trees and spend most of their time feeding on the pollen of flowers. A few species, commonly referred to as twig pruners, will kill small branches and twigs.

Control Methods

Prevention (Non-chemical)

Sanitation and prompt action are the best control against these borers. Felled timber should be removed from the woods as soon as possible. Secondly, the bark should be removed from the logs to prevent infestation. Wounded, damaged, or otherwise weakened areas of the tree are susceptible to borer attack and should be pruned or chemically treated to prevent borer infestation. Trees watered, fertilized, and maintained in vigorous condition suffer few borer attacks.

Treatment (Chemical)

 Insecticides recommended for treatment are given in the Virginia Pest Management Guides available through your local Virginia Cooperative extension office.


Virginia Cooperative Extension materials are available for public use, re-print, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.


Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg.


May 1, 2009

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