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FS ShieldForest Health Protection, Southern Region


Corthylus columbianus (Hopkins)

Importance. - This beetle occurs over much of the East and south to Georgia and Arkansas. It attacks oaks (particularly red oaks), maples, birch, basswood, sycamore, yellow poplar, and elm, damaging the trunks of live trees of all sizes. Damaged wood cannot be used for veneer, cooperage, and furniture.

Identifying the Insect. - Adults are black to reddish-brown cylindrical beetles about 1/5 inch ( 4 mm) long. The larvae are white, legless and C-shaped.

Pupae and adult

Pupae and adult. (Click for detail. JPG 34K).

Identifying the Injury. - Holes less than 1/10 inch (2 mm) in diameter are bored straight into the sapwood until the tunnel nears the heartwood, turning right or left. Damage is conspicuous in log ends. Streaks of stain originating from the tunnels are called flagworm defects.

Staining on bark at point of attack

Staining on bark at point of attack. (Click for detail. JPG 34K).

Biology. - Adult beetles construct galleries. Eggs are laid in chambers along the main tunnel where the larvae live and develop. Larval food is a white fungus that grows on the gallery walls. There are two to three generations per year.

Control. - There is no apparent relationship between tree vigor and susceptiblity. No natural enemies have been found. Protection of veneer-quality trees with insecticides should be considered.