WSU Extension

Hortsense

Arborvitae : Flat-headed and shothole borers
(revision date: 4/23/2014)


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

Non-Chemical Management
  • 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
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images
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Caption: Shothole borer infestation holes
Photo by: A.L. Antonelli
Caption: Shothole borer hole
Photo by: K. Grey
Caption: Bark beetle (very similar to shothole borer)
Photo by: A.L. Antonelli