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Pest Information

Two-lined chestnut borer

Two-lined chestnut borer

  • Latin Name: Agrilus bilineatus
  • Common Name: Two-lined chestnut borer
  • Other Names: N/A

Pest Details

Two-lined chestnut borer


This is a native species in eastern North America.


While this beetle was named for its previous status as a pest of chestnut trees, it now attacks primarily oaks, and will feed on many oak species in the eastern half of North America. Trees that are under stress from other factors, such as defoliation by caterpillars, are at particular risk. Adult beetles are active from spring to summer and females fly to upper branches to feed on foliage prior to moving back to major branches and trunks, where the female then deposits eggs in crevices in the bark. The larvae bore into the tree to feed in the cambium layers, potentially girdling the tree and cutting off nutrient and water flow.


Trees infested with the beetle will show wilted leaves on outer branches early in the season. The leaves eventually fall and that area of the branch will die. Exit holes of the adult beetles will be found on the large branches and these have a very distinctive “D” shape, differing from the round or oval exit holes of most other small beetles in this family. The adult beetles range from ¼ to ½ inch long and are black with 2 golden stripes running front to back on their elytra. They are long and cylindrical in shape. The larvae are typical of flat headed borers, with elongate white bodies that are flattened, and with the second segment of the thorax behind the head wider than the rest of the body. The feeding galleries under the bark will be oval in profile and filled with the sawdust-like frass as the larvae moves along.

Characteristicts Important to Control:

Control is difficult once the larvae are feeding within the tree, but they may be killed by systemic insecticides injected into the trunk. Adult beetles may be killed if contact insecticides can be applied to the trunk timed to the first presence of the adult beetles. Healthy trees are generally able to withstand the presence of some of the larvae, so good tree health is important. A number of parasitic wasps also help to reduce the numbers of larvae that survive in the tree.

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