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FS ShieldForest Health Protection, Southern Region

RED OAK BORER,

Enaphalodes rufulus (Haldeman)

Importance. - This is a major pest of red oaks, accounting for millions of dollars in losses from defects and degrade in lumber. Valuable shade trees in parks and cities are sometimes attacked, but are rarely killed.

Identifying the Insect. - Adult borers are longhorned beetles. Their antennae are very long, almost doubling their 1 -inch (25 mm) body length. Their rust brown color blends well with the bark surface, and they are rarely seen. The pale, robust larvae have very small legs on the thorax.


Adult

Adult. (Click for detail. JPG 47K).


Identifying the Injury. - The first signs of attack resemble the fine frass produced by ambrosia beetles. As the larvae bore into the tree, sap begins to extrude from the attack points. Within the tree, tunnel diameters gradually increase from pinhole size to about 1/2 inch (12 mm) in diameter as larvae grow. Tunnels are 6 to 10 inches (15 to 25 cm) long and are often accompanied by discolored and decaying wood. They are usually within 6 inches (15 cm) of the pith.

Biology. - The red oak borer has a 2year life cycle. Eggs are laid in midsummer in roughened areas or near wounds, and larvae tunnel under the bark for the first year. In the second year, the more damaging wood tunneling commences. Prior to pupation, the larvae chew round exit holes through which they later emerge as adults.

Control. - Removal of brood trees significantly reduces the pest population. Measures aimed at encouraging stand vigor will discourage attack. Infested, high value shade trees may be treated with insecticides.