Two-lined Chestnut Borer - Agrilus bilineatus

The two-lined chestnut borer an endemic beetle native to North America that attacks stressed or weakened oak trees. Larvae of the beetle construct galleries in the inner bark of trees, cutting off the flow of water and other nutrients.  This causes drought-like symptoms and tree death from the top down.  Two-lined chestnut borer is found throughout the eastern US and west to the Rocky Mountains.  Alone, two- lined chestnut borer may act as a natural thinning agent for aging or weakened stands.  However, combined with other stresses, (ex. European Gypsy Moth defoliation), two-lined chestnut borer may become a more significant cause of mortality.

Robert A. Haack, USDA Forest Service, Bugwood.org