Adult flatheaded apple tree borers are approximately 1/2 inch in length with a flattened appearance. They vary in color from a dark metallic brown to dull gray or may appear greenish bronze and brass colored. Some adults of this species emerge from pupation in the spring, while others continue to emerge throughout the summer and into the fall as local temperatures allow. Females may lay approximately 100 eggs during their lifetime, and hide them singly in bark crevices. Larvae are legless, yellow-white in color, with black heads and an expanded region just behind the head. They enter the bark just behind where the egg is laid, especially if the host plant is otherwise stressed or the egg was laid in an area with damaged bark. Healthy and vigorous trees may be able to kill the larva with heavy sap flow. Flatheaded apple tree borer larvae that are successful in boring into their hosts create long galleries just beneath the bark, feeding in the phloem. Tunnels may become partially filled with sawdust-like frass or excrement. Injured areas beneath the bark may become depressions and the bark may eventually split at these locations. As the larva reaches maturity, it bores deep into the heartwood where it pupates. This occurs either in the fall or the spring. After adults emerge, they may do some feeding at the base of twigs, however it is the larval or immature stage of this insect that primarily does the most damage to its hosts.
Larvae of this insect may girdle trees, particularly those that are under additional abiotic and biotic stress. Newly transplanted trees and shrubs are often most susceptible to injury from the flatheaded apple tree borer or other native wood-boring buprestid beetles.
Look for signs of dieback on branches. Larval activity may be detected by observing white, frothy sap oozing from cracks in the bark. Look for galleries created by the larvae in areas where bark is cracking. Adults may be seen occasionally.
Regular fertilization and irrigation or managing host plants to reduce their stress, including planting trees and shrubs on the right site under the proper growing conditions will greatly reduce the potential for attack by the flatheaded apple tree borer. Avoid planting trees too deep, as those conditions are apparently very attractive to this wood boring beetle. According to some reports, horticultural tree wraps used around the trunks of newly transplanted trees may help reduce the chances of flatheaded apple tree borers becoming established. Keep newly planted trees and shrubs vigorous until their root systems are established at the new location.
The flatheaded apple tree borer is a native insect and has natural enemies that help manage populations. These include the ichneumonid wasps Labena grallator and Crytohelcostizus chrysobothridis, the chalcid wasp Phasgonophora sulcata, and the braconid wasp Atanycolus rugosiventris. Predators include the clerid beetles Chariessa pilosa and Chariessa pilosa onusta, the asilid fly Andrenosoma fulvicaudum, and various woodpeckers.
Abamectin (NL)
Acephate (NL)
Azadirachtin (NL)
Bifenthrin (NL)
Chlorpyrifos (N)
Cyantraniliprole (NL)
Emamectin benzoate (L)
Flonicamid+cyclaniliprole (N)
Imidacloprid (L)
Neem oil (NL)
Permethrin (L)
Pyrethrins (L)
Pyrethrin + sulfur (NL)
Spinosad (NL)
Active ingredients that may be applied systemically include: abamectin (injection), acephate (injection), azadirachtin (injection, soil drench), cyantraniliprole (soil drench, soil injection), emamectin benzoate (injection), imidacloprid (soil drench), and neem oil (soil drench).
When used in nurseries, chlorpyrifos is for quarantine use only.
Make insecticide applications after bloom to protect pollinators. Applications at times of the day and temperatures when pollinators are less likely to be active can also reduce the risk of impacting their populations.
Note: Beginning July 1, 2022, neonicotinoid insecticides are classified as state restricted use for use on tree and shrub insect pests in Massachusetts. For more information, visit the MA Department of Agricultural Resources Pesticide Program.
