Arborvitae: Flat-headed and shothole borers

Biology

Flat-headed borer attacks are most severe on declining plants. The 1⁄2″ adults are either brown to metallic gray or black with red or orange markings, depending on species. The larvae mine under bark and may girdle plants. Weeping sap, depressions in the bark, and split bark are symptoms of feeding. Shothole borers are primarily a concern on weakened or declining plants. The adults are small (1⁄10″), red-brown to black beetles. They feed on twig tips of healthy plants, mining the terminal portions for about 6″. Damaged tips die back, producing symptoms of flagging which may be conspicuous in ornamentals. The larvae (bark beetles) feed beneath the bark on the trunk, leaving characteristic “shothole” symptoms (tiny holes in the bark) when they emerge. Larval feeding may also be associated with weeping sap on the trunk.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

• Provide proper culture.
• Healthy plants are less likely to be attacked by boring beetles.
• Avoid wounding plants, which may attract adult beetles.
• Follow recommended transplant methods

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

• None recommended

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