Forest Pests: Insects, Diseases & Other Damage Agents

The bronze birch borer attacks weakened or injured yellow and paper birch trees, as well as gray birch, black birch, poplar, cottonwood, and willow. Usually, the first sign of infestation is browning of the foliage in the upper branches. The tree then slowly declines and eventually dies. Infested branches often appear swollen and discolored.

Full-grown grubs overwinter in cells within the sapwood. From late April until August, adult beetles emerge to lay their eggs beneath flaps of loose bark or lichen, or in cracks or crevices in the bark. The beetle is greensih bronze, ¼ to ½ inch long, with a blunt head and slender, pointed body. When the eggs hatch, tiny larvae bore their way to the inner bark. The larvae are slender with a slight enlargement of the body behind the head. They have two brownish spines at the end of their abdomens. In the fall, after forming cells in the sapwood, the full-grown larvae make galleries between the wood and the bark and pack them tightly with sawdust. These galleries run across the grain of the wood, often girdling the trees. Some galleries may be 4 feet or more in length. Two years are required to complete the life cycle in the North; there is one generation per year in the South.

Larva(e); larva and galleries Photo by David G. Nielsen, Ohio State University

[ Contents ]     [ Previous ]     [ Next ]     [ Home ]