Flatheaded Appletree Borer

flatheaded borer


All fruit trees


Two species occur in the Intermountain West, Pacific and appletree flatheaded borers. Larvae overwinter inside the tree, and emerge as adult beetles in June-August (northern Utah). This insect is usually only a problem on stressed trees (drought, wounding, etc.) or when populations are high in an area. Apple and peach seedlings have been attacked under these conditions


Oval-shaped exit holes; sawdust-like frass; loose, dead tree bark. The larvae can eventually girdle trunks which will kill young trees and heavily-attacked trees.


Watch for adult beetles May-July.

Treatment Threshold

No threshold determined.

Degree Day Model


Management Considerations

The key to management is to maintain healthy trees and remove sources of beetles, such as old orchards. Preventive trunk sprays may be necessary to kill larvae before they tunnel into trunks.