Common name: Flat-headed apple tree borer
Scientific name: Chrysobothris femorata
Hosts: The flat-headed apple tree borer (Chrysobothris femorata) is a common species that feeds on many deciduous shade and fruit trees. Common hosts include apple, black walnut, silver maple, white and black oak, pear, hickory, willow, sycamore, and tuliptree. Newly transplanted trees and trees under stress are particularly susceptible. Healthy trees can often tolerate some damage from the borer. The flat-headed apple tree borer is native to much of North America.
Damage
Flat-headed apple tree borer adults will feed on leaves, but this damage is relatively minor. The real damage is done by the larvae, which tunnel under the bark into the vascular tissues. The larvae produce long tunnels, but will partially fill them with excrement. This damage can girdle a tree, leading to dieback of branches.
Areas where larvae are tunneling can often be identified by sap oozing out of cracks in the bark. These cracks can become entryways for secondary pests and diseases.
The borer can attack both weakened and healthy trees. In healthy trees, the larvae may be killed by a heavy flow of sap and this can minimize damage.
Life Cycle
Flat-headed apple tree borer overwinters as pupae in the heartwood of the tree. Adults begin to emerge from the tree in spring, and adult emergence can continue throughout summer.
The adult borer is a beetle about ½-inch long, somewhat flattened and varying in color from dark brown to gray.
Newly emerged beetles will feed and then mate.
Each female can lay about 100 eggs. The eggs are laid in the crevices of the bark and are laid singly, rather than in masses. The eggs hatch into cream colored larvae.
The larva has a very small black head and behind the head is an obvious flattened segment which gives this insect its common name. The newly hatched larva enters the bark near the areas where it hatched out of the egg. The larvae spend the season making long tunnels under the bark and feeding on the vascular tissues.
As they mature, the larvae bore into the heartwood of the tree and enter into the pupal stage for the winter.
There is one generation per year.
Management
Cultural Management
Trees and shrubs of low vigor, or in a weakened state of health, are especially susceptible to borer attack.
Prevention is the key in controlling wood-boring insect pests.
Grow only trees and shrubs that are adapted to the area and site. Keep plants healthy and vigorous through proper planting, mulching, watering, fertilizing, pruning, and winter protection practices. Protect trees from injuries. Remove dead limbs or trees promptly to avoid infestations. Remove bark from felled trees if stored for firewood.
Biological Management
There are naturally occurring enemies of this native pest. These include some species of parasitic wasps and predatory beetles, as well as woodpeckers. These natural enemies can help reduce borer populations, but will not always give complete protection.
Chemical Management
Systemic insecticides and trunk sprays are available to manage this pest.
The pesticide information presented in this publication is current with federal and state regulations. The user is responsible for determining that the intended use is consistent with the label of the product being used. The information given here is for educational purposes only. Reference to commercial products or trade names is made with the understanding that no discrimination is intended and no endorsement made by The Morton Arboretum.
For more information, contact The Morton Arboretum Plant Clinic at 630-719-2424 or plantclinic@mortonarb.org.