Common Insects and Mites: Bark beetles

Biology

One or more species of bark beetle attack virtually all trees in the Pacific Northwest. Most bark beetles are secondary pests, attacking trees already stressed from other causes. However, one particular group, the turpentine beetles, attack the collar area of some conifers, and are considered primary pests. Bark beetles measure from 1/8″ to 1/4″ long, and may appear cylindrically-shaped, and shiny brown or black with a somewhat reddish tint. Adults, larvae, or pupae overwinter under bark. Adult beetles emerge in the spring (around May), leaving tiny “shotholes” in the bark. Some have more than one emergence period. Adults feed on bark, occasionally girdling and killing entire trees. After feeding, the adult beetle lays eggs in galleries under the bark of branches, trunks, or in branch crotches of diseased or weakened trees. Adults will also lay eggs in recently cut wood when the bark is intact. The adult galleries are typically arranged parallel to the grain of the wood, while the larvae make secondary galleries more or less perpendicular to the main gallery. Beetles emerging from trees will seek out and infest other trees. The beetles must be present in sufficient numbers to overcome the resistance of the host tree. Trees attacked by bark beetles rarely survive. Uniform, single-species stands of older trees are particularly susceptible.

Management Options

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

Non-chemical Management

Select non-chemical management options as your first choice!

• Avoid injury to trees, especially during spring and summer. Adult beetles are attracted to wounds.
• On elm, control of bark beetles is essential to prevent the spread of Dutch elm disease.
• Maintain plant health. Healthy plants are less susceptible to infestation. Select the proper plant for the site and provide proper cultural care.
• Remove damaged or infested limbs in spring before adult beetles emerge. Also remove dead or dying trees. Remove and destroy bark from freshly cut wood, or burn or bury wood.

Chemical Management

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

Chemical control of bark beetles is not 100% effective. If a pesticide is used, apply material registered for use on the host plant to the trunk and lower limbs. Avoid contacting foliage. Apply generally in late spring or when adults are active.

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