Forest Health: Twolined Chestnut Borer

The twolined chestnut borer, Agrilus bilineatus (Weber), belongs to the beetle family Buprestidae. The word "chestnut" refers to the beetle's past status as a principal pest of American chestnut, Castanea dentata.

The twolined chestnut borer is found from the Maritime Provinces of Canada, west to the Rocky Mountains, and south to Florida and Texas.

This slender black beetle has impacted oak-hickory stands in the northern portion of the Daniel Boone National Forest. Oaks are the primary host for this pest, causing mortality in the oldest and weakest trees. Infestations are a reflection of forest age and environmental stress.

Importance. This borer attacks red and white oaks throughout the East. Trees weakened by drought, insect defoliation, or other factors are most susceptible. Larvae mine the cambium, resulting in girdled trees. Mortality can be extensive in weakened stands.

Identifying the Insect. Adult beetles are about 1/5 to 1/2 inch (6 to 12 mm) long, slender, and black, with a light yellowish stripe on each wing cover. Larvae are white, slender, flattened, and about 1 inch (25 mm) long, with two spines at the rear end.

Identifying the Injury. Larvae excavate winding mines in the inner bark and outer sapwood of the main trunk and large branches, frequently girdling the tree. Attacks usually begin in the upper tree canopy and extend downward as the tree continues to weaken. D-shaped adult emergence holes are evidence of infestation.

Biology. Adults emerge during spring and early summer and deposit eggs in bark crevices. Eggs hatch in 10 to 14 days. The larvae burrow through the bark and cambium. They overwinter in cells in the bark and pupate the follwing spring. There is one generation per year.

Control. Control is mainly a matter of preventing attacks through cultural practices that promote tree vigor. Spraying to protect foliage from insect defoliators is recommended in some areas.

Forest Insect and Disease Leaflet on Twolined Chestnut Borer

Forest Pests of North America

Forest Health Protection Southern Region

Insect Threats

Gypsy Moth | Hemlock Woolly Aldegid | Southern Pine Beetle | Sudden Oak Death

Other Forest Health Topics

Four Threats to Forest Health | Forest Health Initiative | Red cockaded woodpecker | Invasive Species | Prescribed Burning

Title: Chestnut Borer
Last Updated: July 27, 2009