Twolined Chestnut Borer
Agrilus bilineatus |
| USDA Forest Service. 1979. A guide to common insects and diseases of forest trees in the northeastern United States. Northeast. Area State Priv. For., For. Insect and Disease Management., Broomall, PA. p. 123, illus. |
The twolined chestnut borer attacks various hardwoods, especially chestnut and several species of oak. Trees weakened by drought or defoliation are most susceptible to attack. Larvae mine in the inner and outer wood, and a heavy attack may girdle and kill the tree.
Beetles overwinter as pupae in cells constructed in the outer layers of sapwood and sometimes in the bark. In spring the adults emerge through characteristic D-shaped holes in the bark. Eggs are deposited on the bark in late spring and early summer. Young larvae bore directly through the bark to the phloem, where they excavate winding galleries in the inner bark and outer wood of the main trunk and larger branches. Mines run back and forth in all directions. Heavily attacked trees are girdled and eventually die. The attack usually begins in the top of the tree, extending downward as the tree weakens. In the North, the beetle has a 2-year cycle; in the South, only 1 year is required.
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