Peachtree Borer, Synanthedon pictipes
Peachtree borers are the most destructive pest of stone fruits such as peach in Colorado. The larvae chew underneath the bark of the tree which can weaken and sometimes kill the plant.
Description and Life Cycle
Larvae of the peachtree borer cause damage to fruit trees. Upon hatching from eggs, young larvae immediately tunnel into the sapwood of the tree, usually through cracks and wounds in the bark. Larvae range from 1.25 to 3.5 cm in length and are white with a brown head. The grub-like larvae chew underneath the bark at the base (crown) of the tree and on larger roots.
The insects spend winter as partially grown larvae below the ground or under the bark. With the return of warmer soil temperatures larvae resume feeding. Most injury is produced in mid-to late spring as the larvae mature. The larvae complete their development and pupate in late May through early July. Pupation occurs in a cell made of silk, gum and chewed wood fragments, located just below the soil surface.
The adults emerge within a month and in the process often will pull out the pupal skins, which may be seen around the base of the trunk. Adults of the peachtree borer are also known as clearwing borer moths that somewhat resemble wasps and are active during the daytime. Adults are dimorphic – females and males have distinct body and wing coloration. Females have one broad orange band across the abdomen while males have two or more smaller bands across the abdomen.
The first adults, males, may emerge as early as mid-June. Females usually follow by a couple of weeks. Mating and egg laying occur during July and August, and female moths lay eggs on the bark of the lower trunk and in soil cracks near the tree base. Eggs generally hatch in about 10 days.
James Solomon, USDA Forest Service, Bugwood.org.
Peachtree borer injury at the base of a young peach tree.
Eugene E. Nelson, Bugwood.org.
Peachtree borer larvae on peach tree roots.
Joseph Berger, Bugwood.org.
Adult male and female peachtree borers.
- The peachtree borer is the most destructive insect pest of peach, cherry, plum, and other stone fruits in Colorado
- Injury results from larval feeding, which chew beneath the bark of the lower trunk and larger roots. Adult peachtree borers are a clear-winged moth which are active during the day
- Insecticide sprays applied to the lower trunk when eggs are being laid can prevent new infestations
All stone fruits in the genus Prunus, which include peach, cherry, plum, prune, nectarine, apricot, and several ornamental shrubs are susceptible to damage by the peachtree borer. The gouging wounds produced by larval feeding can be extensive and may seriously weaken or kill the tree, but it may not be obvious unless the area around the base of the tree is examined closely. External evidence of peachtree borer tunneling is a wet spot on the bark or presence of oozing, gummy sap. Most injuries occur along the lower trunk beneath the soil line. Lower branches rarely receive injuries. (Note: Oozing wounds on peach that produce an amber-colored gum may be caused by cytospora canker. Information about this fungal disease can be found here).
Traps can be used to determine when adult peachtree borers are locally active. Various designs of traps, usually with a sticky bottom, are used to capture adult males. Moths are are lured into the trap by a chemical (sex pheromone) that mimics what female peachtree borers use to attract mates. When adults are found in the traps, it indicates that mating and egg laying is taking place. Larvae can be removed from the bark using a knife; however, care must be taken not to cut into undisturbed bark.
Peachtree borer is most easily controlled by sprays of insecticides applied to the lower trunk and base of the tree. These are preventative sprays that target the eggs and early larval stages exposed to the bark of the tree. Once larvae have migrated into the tree, insecticides are not effective. Since egg hatch begins about 9-10 days after the moths emerge, insecticidal sprays should be applied 7-14 days after the first peachtree borer moths are captured in the traps. Generally, trunk sprays should be applied around the first week of July. To be effective, the insecticide must have some residual activity, allowing it to kill young peachtree borer larvae emerging from eggs for several weeks after application.