Two Lined Chestnut Borer

The two-lined chestnut borer is a serious pest which most frequently attacks oaks, chestnuts and beech. The larvae from this insect form meandering galleries in the phloem, which can be seen under peeling or stripped bark on infested branches or stems. Reduced uptake of water and nutrients in infested trees causes leaf wilting and dieback from the top of the tree downward. There is a "dead, red, green" appearance from the top down. This is from dead leaves, wilting leaves and then the green leaves of the host tree. Even after normal fall leaf drop, many of the effected dead, brown leaves will remain attached to the tree. The larvae are white, segmented, flattened and about 2.5 cm long when mature. The beetles are 6-10 mm in length and bluish-black as adults. This pest gets its name from the two pale lines which run the length of the wing covers. The adults emerge through D-shaped exit holes, and generally begin to appear in early June.

The best protection from the two-lined chestnut borer is prevention. This pest attacks weakened and stressed trees, so attention should be given to maintaining tree health by watering during drought, mulching, and minimizing damage to the root zone that could cause root injury and stress. When symptoms of two-lined chestnut borer are visible it is nearly impossible to save the infested limbs. These branches and deadwood should be removed if choosing to save the tree. High value trees at risk for infestation by the two-lined chestnut borer may be treated preventatively with a pesticide soil injection in the fall or early spring. Trees infested with two-lined chestnut borer may be similarly treated, although trees with serious decline are unlikely to be saved.

Contact Plant Health Solutions for proper diagnosis and to develop a treatment plan. 

  • Two-lined chestnut borer
  • Two-lined chestnut borer
  • Two-lined chestnut borer
  • Two-lined chestnut borer