|Flatheaded Borer - Chrysobothris mali
Larvae Damage on Tree
USDA Forest Service,
www.forestryimages.org University of Georgia / USFS
fruit, forest, and shade trees. Ash, Maple and apple are the most common
hosts. Arborvitae are attacked by a related species.
are pale yellow and legless with an enlarged, flattened thorax. Adults
are dark olive-gray brown metallic wood boring beetles about ½”
stages tunnel under the bark of trunks and larger branches producing a
fine sawdust frass. Tunneling may girdle and kill young trees. Injuries
are concentrated on the sunny side of trees. Beetles most commonly
attack trees suffering sunscald, wounds or drought stress.
CYCLE: Larvae over winter in host plants. In spring, they pupate and bore holes in the host tree. Adults emerge in late spring and lay eggs which hatch into larvae in late summer.
Cultural: Attacks by flatheaded borers are
concentrated around wounds, cankered areas, and on drought-stressed
trees. Healthy trees are less attractive to egg laying
females. Larvae are often killed by the trees defense system which
oozes sap. Dying trees and newly cut wood should not be kept near
susceptible trees since large numbers of borers can develop in these
materials. Once borers are present in the trunk, digging them out in
late summer or early fall is the only control. This is difficult to do
without causing additional injury.
Chemical: Spinosad can be applied in late spring to tree trunks.