How to Manage Pests

Pests in Gardens and Landscapes

Flatheaded borers

Adult borers are beetles that are often metallic (coppery, blue, black, or green), particularly on the lower surface and upper abdomen. Their bodies are flattened, elongated or oval, and typically have longitudinal grooves on the wing covers. The larvae are light colored and have a distinctive shape with a flattened enlargement just behind the tiny head.

Identification of species | Life cycle


Flatheaded borers attack aboveground portions of trees that have been previously injured by sunburn or other causes. Tunnels excavated beneath the bark by the borer larvae may cause a wet sappy area on the bark of the main trunk, which may later crack. Limbs or trees may be killed.


Prevention is the most effective management. Stressed trees are most likely to be damaged. Properly plant species that are well adapted to that location and provide them with proper care. Avoid pruning from spring through summer when adults are active. Protect trees from injury. Remove and dispose of dying limbs and dead trees. Do not pile fresh-cut wood near trees; beetles may emerge from it and attack nearby plants. Provide proper irrigation. Sprays are not generally recommended, but may provide some control when treating adults of alder and bronze birch borers.

Flatheaded borer
Pacific flatheaded borers larva

Rough bark
Rough bark caused by the flatheaded borer

Statewide IPM Program, Agriculture and Natural Resources, University of California
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