WHAT IS THE BRONZE BIRCH BORER?

The Bronze Birch Borer Agrilus anxius Gory is a wood-boring Buprestid beetle native to North America. Bronze birch borer adults are slender, dark, iridescent, often greenish bronze beetles, 7-12mm long.

Hosts

While all species of birch can be attacked, White-barked Birch varieties are more susceptible than others.

SYMPTOMS

Bronze Birch Borer injury includes dieback that begins in the upper portion of the tree’s canopy, a lumpy appearance to branches where galleries are present, and D-shaped exit holes in the bark created by emerging adults. Rusty-colored stains may also be visible on bark in the area of entrance or exit holes

Treatment Timing and Prevention

Plant Birch in a cool, moist, shaded environment. They do not grow well in an open, sunny, exposed area, such as the middle of a large, open yard or the exposed south or west side of a building. Further, this species prefers to l ay eggs on trees growing in full sunlight. Keep birch trees healthy by watering and fertilizing as needed.

Soil-applied systemic insecticides as well as trunk injections, for the larger trees, have been shown to greatly reduce injury and protect the tree(s) from this pest.

Insect Life Cycle

The adult female deposits her eggs in the cracks and crevices of susceptible Birch trees in late May or June. The larvae hatch about ten days later, boring into the wood of the host tree and feeding on interior tissue of the bark. They continue to mine their intricate feeding tunnels actively until fall, then form a cell at the end of a tunnel where they overwinter. Larvae pupate the following spring and emerge as adult beetles through telltale “ D-shaped “ holes cut into the bark. Adults feed on the tender young foliage for about a week before laying their eggs and can be seen moving around the sunny side of the tree.

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