Key Features
- D-shaped holes in trunk
- Zig-zag pattern under bark
- Metallic adult beetles
Symptoms
Flatheaded apple tree borer is a common problem for trees subject to the stress of transplanting. Infested trees can be killed outright by the girdling grubs, or be snapped in half during a wind storm after the late stage weakens branches by feeding in the heartwood of limbs. Beetles will often attack south sides of the trunk causing splits and cracks. Mature white, larvae are up to 1" long. Metallic adults emerging from "D" shaped exit holes are 1/2" long and metallic.
Biology
Wintering as a pupa or late stage grub, most adults emerge in May and fly throughout the summer. Adult females lay single eggs on the bark surface in cracks and crevices that hatch into larvae that bore beneath the bark to feed on the vascular tissue beneath. Later stage grubs bore into the heartwood and weaken limbs. There is one generation per year.
Management Recommendations
Minimize plant stress during the first three years after transplanting through adequate watering and wrapping trees to prevent frost cracking. Consider applying an insecticide to the trunk (permethrin, bifenthrin), before adults begin to fly, and again in July to protect these trees. A soil insecticide (imidacloprid or dinotefuran) can be applied as an alternative once each year. Be sure to wait until after maples have completed flowering to apply these soil insecticides. Nursery producers can use products containing imidacloprid and cyfluthrin.
Effective Pesticides
Active Ingredients include: Bifenthrin, Cyfluthrin, Dinotefuran, Imidacloprid, Permethrin
Resources
