Flatheaded Appletree Borer

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Order	Coleoptera
Suborder	Polyphaga
Infraorder	Elateriformia
Superfamily	Buprestoidea
Family	Buprestidae
Subfamily	Buprestinae
Tribe	Chrysobothrini
Genus	Chrysobothris

Scientific Name

Chrysobothris femorata

Common Name

flatheaded appletree borer

Compiled by Whitney Cranshaw, Colorado State University:
Chrysobothris femorata (Olivier)
Coleoptera: Buprestidae

Hosts

Flatheaded appletree borer has a very wide range of food plants including most deciduous fruit, forest and shade trees. Maples and apple are among the more common hosts.

Damage and Diagnosis

Damage caused by flatheaded appletree borer larvae.

The immature stage (a flatheaded borer) tunnels under the bark of trunks and larger branches, producing broad galleries that are tightly packed with fine sawdust frass. Areas of bark where injury has occurred often appear darkened, somewhat sunken and later may split above injuries. On young trees tunneling may girdle and kill the plant; tunnels are more restricted in area on established trees. Injuries are concentrated on the sunny side and most commonly occur on trees suffering sunscald, wounds or that suffer from drought stress.

Life History and Habits

Larvae of the flatheaded apple tree borer.

Larvae are a typical "flathead borer" - pale yellow, legless with a very enlarged thorax. Winter is spent as a larva under the bark. They complete development the following spring, cut a chamber into the sapwood and pupate. Adults may begin emerging by mid spring but peak activity is from late May through June. Adults are dark olive-gray to brown metallic wood borers about 1/2 inch long. The females may be observed searching the sun-exposed sides of trunks of host trees. Eggs are laid singly in bark cracks or near existing injuries and over the course of a month may lay about 100 eggs. Eggs hatch within 8 to 16 days and the larvae chew through the bottom of the egg and begin to tunnel into the tree. Larval development can be rapid and gallery formation extensive in low vigor trees. Development is retarded and tunneling more restricted in trees of high vigor. They continue to feed for several months, becoming dormant during the cold season. There is one generation per year.

Related Species

Two closely related species occur within the region. The Pacific flathead borer (Chrysobothris mali Horn) predominates in the west of the Rockies; the flatheaded apple tree borer in the east. However, their ranges may overlap in the region. Biologies of the two species are similar.

Management

Attacks by flatheaded apple tree borer are concentrated around wounds, cankered areas, and on trees in generally poor health. Healthy trees are less attractive to the egg laying females and the tunneling larvae often are killed by tree defenses, such as oozing sap. By maintaining trees in a healthy, vigorous condition and preventing injuries, problems with these insects can be avoided.

Where sunscald injuries are likely, shade the lower trunk of young trees or use tree wrap to prevent this injury. Whitewashing the trunks can also reduce attacks.

Dying trees and newly cut wood should not be kept near susceptible trees, since large numbers of borers can develop in these materials.

Once the borers are in the trunk, digging them out in late summer or early fall is the only control. This is difficult to do without causing additional tree injury.

Preventive use of insecticides, applied to trunks and branches can limit new attacks. Treatments should be timed to coincide with periods of egg laying and egg hatch.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.