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Bark Beetles

Pest

Bark beetles are small wood boring insects that tunnel beneath the bark of trees and shrubs. They are significant because their feeding galleries disrupt the flow of water and nutrients, which can lead to the rapid decline or death of the host plant.

Bark Beetles on a plant
Photo: Gilles San Martin, CC BY-SA

Symptoms by part

Stems

Small circular exit holes on the bark surface, piles of fine sawdust or frass around the base of the trunk, and patches of discolored or wilting foliage.

Causes

  • Drought stress that weakens the tree defense system.
  • Physical damage to the trunk from lawn equipment or storms.
  • Overcrowded planting conditions that limit airflow and vigor.
  • Presence of dying or recently fallen wood nearby that attracts breeding populations.

Could be confused with

  • Ambrosia beetles · Ambrosia beetles push out toothpick like frass tubes from their entrance holes, whereas bark beetles typically leave fine, powdery dust.
  • Woodpecker damage · Woodpeckers create large, ragged holes while hunting for larvae, while bark beetle exit holes are perfectly round and tiny.

Treatment

  1. Prune and destroy infested branches immediately to reduce the local beetle population.
  2. Remove and dispose of severely infested trees to prevent the spread to healthy neighbors.
  3. Water trees deeply during dry spells to help them maintain the sap pressure needed to push out invading beetles.

Without chemicals

  • Keep trees healthy with proper irrigation to ensure they can produce enough resin to repel attackers.
  • Remove dead or dying wood from the landscape to eliminate breeding sites.
  • Avoid wounding trunks with lawn mowers or string trimmers.

Chemical options

  • Lambda-cyhalothrin, apply as a trunk spray to the bark during the adult flight period, follow the label.

Preventing it

  • Maintain high tree vigor through consistent watering during dry periods.
  • Promptly remove any storm damaged or dead wood from the property.
  • Thin out overcrowded stands of trees to improve overall health and reduce stress.

Season

The warm growing season when temperatures are high enough for adult beetle flight and colonization.

Spread risk

Moderate

Severity

High

When to act

Act as soon as you notice sawdust or exit holes on the trunk. If the tree shows widespread canopy dieback, it is likely too late to save and you should hire a tree surgeon to remove it safely.

Think it's Bark Beetles?

This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Can I save a tree once bark beetles are inside?
If the infestation is light and the tree is otherwise healthy, you may be able to save it by improving its water intake and removing infested limbs. If the beetles have already girdled the trunk, the tree will not recover.
Do bark beetles attack healthy trees?
While they prefer stressed or dying trees, large populations can sometimes overwhelm and kill healthy trees by sheer force of numbers.

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This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.