Family- Sesiidae

The lesser peachtree borer was first reported in Pennsylvania in 1868. Since then, it has been found in all sections of the United States and Canada. In many respects, the lesser peachtree borer is similar to the peachtree borer. It differs from the peachtree borer in that the moths emerge over a long time during the summer. Also, the larvae do not confine their activity to the trunks, scaffold limbs and branches.

Egg: Eggs of the lesser peachtree borer are cinnamon- or rust-brown and oval in outline, and they average 0.62 mm long by 0.39 mm wide. The surface of the egg is finely netted. Egg incubation takes from 7 ½ to 8 ½ days.

Larva: The larva of the lesser peachtree borer is similar to that of the peachtree borer and other clear-wing moths. The length of the full-grown larva is 20 to 26 mm. The head is yellowish brown, the cervical shield is light yellow, and the body is creamy white, sometimes tinged with pink and slightly translucent. The larva has three pairs of short thoracic legs. Abdominal prolegs are almost absent but bear one transverse band of crochets (hooks).

Newly hatched larvae are about 0.65 mm long. The head is yellowish brown and the body is translucent white. Larval growth is completed after six larval stages, or instars.

Cocoon: Cocoons are from 12 to 20 mm long and elongated. They are constructed from chips of bark and frass held together by silken strands. New cocoons are light yellowish brown; older ones are rust-colored. The pupation period during May averages about 23 days.

Pupa: Pupae vary from 10 to 17 mm long. They are elongated and cylindrical and light tan. The head has a hard chitinized cutting plate for cutting through the cocoon. Wings, legs and mouthparts are identifiable on the ventral (underside) side of the pupa. Abdominal segments have rows of spines on the seventh abdominal segment; female pupae have only one row.

Adult: Both sexes have clear wings; the only colored areas are the wing edges and veins. The head, thorax, body, legs and antennae of both sexes are metallic blue-black with pale yellow markings. The female wing span measures 15 to 26 mm; the male wing span measures 15 to 23 mm. In both sexes, the second and fourth abdominal segments are bordered in pale yellow bands. In general, the male is slightly smaller and more slender. The finely tufted antennae of the male make it easy to distinguish between the two sexes.

Both the male and the female lesser peachtree borer resemble the male peachtree borer. However, the second and fourth abdominal segments of the lesser peachtree borers bear yellow bands, while the male peachtree borer has a yellow band on the posterior margin of each abdominal segment.

Cultivated food plant hosts include peach, plum, sweet cherry, tart cherry, apricot and nectarine. Wild crop hosts include wild black cherry, wild red cherry, beach plum, wild plum and Juneberry. The lesser peachtree borer occurs in all fruit-growing sections of the United States and Canada.

The larvae of the lesser peachtree borer commonly occur under the bark in wounded or injured portions of the tree. They may be found in injured or diseased trunks, scaffold limbs or branches. Pruning wounds, valsa cankered areas, insect-injured areas are locations of infestation. The lesser borer can become established only in tissue preciously injured by some other cause – it cannot establish itself in healthy tissue.

Once established in an injured area, the larvae feed freely on the tender growing bark at the margins of the injured area. If not controlled, they may enlarge the wounded area by feeding until the entire branch or limb is girdle, resulting in death of the limb. Borer infested trees are especially susceptible to attack by the valsa canker fungus organism.

The presence of borers is revealed by the sap flowing from wounded areas, which contains brown frass from the larvae.

Temperature, principally during the spring, probably influences the development of the pupae and the emergence of the adults more than any other factor. Also, favorable high temperatures during the summer induce a partial second generation late in the season. Tree injury from mechanical harvesting that results in bruised or open wounds in the bark of the limbs and trunk of the tree has been chiefly responsible for changing the status of this insect from a minor to a major pest of cherries.

The lesser borer passes the winter in carious stages of larval growth from the second to the sixth instar. In the spring, the larvae feed for a while, then burrow to the surface of the outer bark, leaving only a thin disk of bark over the mouth of the burrow. The larva constructs a cocoon in the burrow from bits of frass and bark. The pupa, with its head directed toward the moth of the burrow, pushed through the cocoon and disk of bark. The pupal stage varies from 20 to 30 days.

During favorable weather, mating occurs within an hour after the moths emerge, and oviposition takes place shortly after mating. The female deposits eggs in cracks and crevices near injured areas. Usually two to four eggs are deposited at a single location. Almost 98 percent of the eggs are deposited in injured areas between ground level and 8 feet up, with the highest percentage being deposited within 3 to 4 feet of ground level.

Depending on the temperature, egg hatching occurs in seven to 10 days. Then the young larvae invade the wounded tissue and start feeding.

Moths of the lesser peachtree borer are in flight from late May through September in the northern states. In the southern states, emergence occurs earlier in the season and there are two complete generations in a year. In the north central states, peak emergence may occur from early June to mid-July, depending on the location. There is a single continuous generation each year, but in some years in some locations, a partial second generation may occur.

Examine the trunk, scaffold limbs and exuded gum for frass. Place pheromone traps in trees early in the season. Depending on location, this may vary from early April to mid-May. In southern locations where there are two generations, replace the caps and traps for the second generation. Because the pheromone for the lesser peachtree borer is species-specific, other clearwing moths such as the peachtree borer and dogwood borer will not be caught in these pheromone traps.

A hydraulic gun with low pressure is used to apply an effective pesticide to the trunk and scaffold limbs. The first application should be made about 10 to 14 days after first emergence. Spray to runoff. Pheromone traps should be employed for timing of male emergence.