American Plum Borer Euzophera semifuneralis (Walker)

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Arthropoda
Subphylum	Hexapoda
Class	Insecta
Subclass	Pterygota
Infraclass	Neoptera
Superorder	Holometabola
Order	Lepidoptera
Superfamily	Pyraloidea
Family	Pyralidae
Subfamily	Phycitinae
Tribe	Phycitini
Genus	Euzophera

Scientific Name

Euzophera semifuneralis

Common Name

American plum borer

Solomon, J. D.; Payne, J. A. A guide to the insect borers, pruners, and girdlers of pecan and hickory. Gen. Tech. Rep. SO-64. New Orleans, LA: USDA Forest Service. Southern Forest Experiment Station; 1986. 31 p.

Importance

The American plum borer, Euzophera semifuneralis (Walker), a pest of pecan and hickory, has a wide host range, being especially troublesome to fruit trees (Blakeslee 1915, Pierce and Nickels 1941). It is widely distributed throughout the United States and is also found in Canada, Mexico, and Columbia, South America (Heinrich 1956, Forber 1890). It is primarily a pest of trees in poor vigor, usually attacking trees that have been mechanically wounded or infected by canker-type fungous diseases. The larvae rarely succeed in establishing themselves on healthy, uninjured trees. Damage results from the larvae feeding in the cambial area, sometimes girdling and killing small trees. It may also be found feeding on the callus tissue of recently grafted or budded trees. Graft failures are sometimes attributed to this borer.

Description

The adult has a light-gray body with grayish-brown forewings that have a broad, wavy band of black and brown markings (fig. 5A) (Blakeslee 1915, Heinrich 1956, Forbes 1890). The hindwings are smokey gray with a distinct black margins. The wingspan ranges from 17 to 25 mm. Eggs vary from dull white when deposited to pink or brown as incubation progresses. Each egg is oval and measures about 0.6 mm long and 0.4 mm in diameter. The larvae is white when newly hatched but the color varies from dull white to pinkish or reddish brown as it developes (fig. 5B). The head is dark brown and the cervical shield is pale yellow with black margins on the sides. Full-grown larvae range from 16 to 28 mm and average about 25 mm in length. The pupa is brownish black and is found inside the white silken cocoon.

Evidence of Infestation

The most obvious sign of infestation is an accumulation of dark-brown or black frass adhering to the bark at the site of attack (Blakeslee 1915, Pierce and Nickels 1941). The frass typically is made up almost entirely of excrement pellets stuck or adhering loosely together by sap exudate and silken threads. Attacks are limited almost entirely to trees with mechanical wounds, frost damage, sun scalds, disease cankers, pruning wounds, and recent grafts and buds. Patches of dead or diseased cambium or partially girdled stems are favored sites for invasion. Larvae, larval burrows that extend into the living tissue, and accumulations of frass can be exposed by lifting pieces of dead bark. The presence of one or more loosely woven cocoons of white silken threads under the bark is very characteristic of the American plum borer. The white silken cocoons distinguish this borer from the dogwood borer, which has dark-brown or black cocoons usually entirely covered with frass. Attacks may be found on trees and branches of all sizes, but they are most commonly found on the lower trunk just above the groundline.

Biology

The insect overwinters as a larva in a white silken cocoon under loose bark near the entrance to its feeding burrows (Blakeslee 1915, Pierce and Nickles 1941). Pupation occurs within the cocoon during March and early April and lasts 20 to 30 days. Adults emerge during April and May. The females mate and begin ovipositing 1 to 3 days after emergence and deposit eggs for 1 to 4 days. Females deposit from 12 to 74 eggs singly on twigs or in small groups in cracks and crevices of the bark of suitable host trees. The eggs hatch in 8 to 14 days and the young larvae seed wounds, cankers, and other suitable sites to begin feeding. The larval development period is 4 to 6 weeks. The mature larvae construct loosely woven cocoons of white silken threads under the bark for pupation. The pupation period for summer broods lasts 10 to 18 days, about half the time required for spring pupation. There are two or more generations per year. Larvae may be found almost continuously, indicating considerable overlapping of broods.

Control

Because the insect is largely incapable of establishing itself in healthy, vigorous, uninjured trees, damage is unlikely except when trees suffer from frost injury, sun scald, mechanical wounds, or canker-type fungous diseases (Blakeslee 1915, Kelsey and Stearnes 1960, Pierce and Nickles 1941). Therefore, good cultural practices that prevent such injuries help to minimize damage from the American plum borer. Five ichneumonid parasites, Mesotenus thoracicus (Cress.), M. gracilis Cress., Itoplectis marginatus (Prov.), Pimpla sp., and Idechthis sp., help to suppress infestations. An unidentified threadworm parasite has also been reared. Predators include larvae of the ostomid, Tenebriodes corlicalis Melsheimer, ants, and woodpeckers. Chemical control is possible but seldom needed.