Flatheaded Appletree and Pacific Flatheaded Borer

Pest Description

• adults: 1/2 – 3/4 inch
• larvae: 3/4 – 1 1/4 inches; creamy white with an expanded, flat head region

Flatheaded Appletree Borer

• body is greenish bronze above and beneath; wing covers with light, zigzag bands

Pacific Flatheaded Borer

• body is brown with gray markings on the wing covers

Host Plants, Diet & Damage

• many hosts: apple, pear, stone fruits, beech, cotoneaster, linden, maple, oak, sycamore, willow, etc.
• feeding beneath bark can kill cambium and sapwood, girdling smaller trees
• attack usually occurs around pre-existing damage
• oozing sap from under the bark of fresh boring wounds
• splitting, peeling or flaking bark
• lumpy, water-soaked areas of bark above larval feeding
• hard-packed frass under flaking bark, or in galleries
• oval-shaped exit holes

Biology, Life Cycle & Damaging Life Stage

• overwinter as larvae under bark, sapwood or heartwood
• adults emerge from late spring to early fall (peak in June and July in northern Utah)
• eggs laid on bark, usually near wounds
• larvae are the damaging stage

IPM Recommendations

• Reduce stress and keep trees healthy and damage free.
• Wrap thin-barked trees with horticultural wrap in the winter.
• Prevent mechanical or environmental injury to trees.
• Apply an insecticide (carbamate; pyrethroid) to bark of stressed or injured trees prior to and during peak beetle flight.

For more information, see our Flatheaded Borers fact sheet.