Flatheaded Appletree Borer and Pacific Flatheaded Borer
Chrysobothris femorata; Chrysobothris mali
Flatheaded appletree borer (Joseph Berger, Bugwood.org)
Flatheaded appletree borer larva (James Solomon, USDA Forest Service, Bugwood.org)
- 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
- 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.