How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Synanthedon exitiosa
(Reviewed 11/09, updated 11/09, pesticides updated 9/15, corrected 1/19)
In this Guideline:
Description of the Pest
Peachtree borer eggs are laid during the summer on the bark of trees. Larvae overwinter in the tree trunk. They feed in the crown area and burrow up into the tree. At maturity, a larva is about 1.25 inch long and has a light-colored body and a dark head. In late spring, larvae pupate near the entrance of their burrows or in the soil. Adults emerge from May through September; they are steel-blue to black clearwing moths with a 1-inch wingspan.
Peachtree borers can girdle and kill young trees. Older trees can withstand the damage unless there are many larvae or the tree is attacked several years in a row.
Look for the presence of frass and gum at the bases of trees when monitoring orchards in spring. Also check trees in the fall for signs of peachtree borer activity. At this time, you can kill larvae by carefully using a knife or wire to probe the trunk. Mark any that you find, and return to treat them the following spring. Treat by spraying the tree trunk from the scaffold to the soil line. Apply the insecticide with a hand-held sprayer to the tree trunk from the juncture of the main scaffold limbs to the soil line. Cover the trunk thoroughly, using enough spray material so it will run off to form a small puddle at the base of the tree. Use from 0.5 to 1.5 gallons per tree, depending upon the size of the trunk. Remove suckers and pull soil away from the base of the tree before treating. Two applications are recommended to protect during the prolonged period when adults are active, one in mid-May when adults are first detected and one in the middle of July. Be careful to observe preharvest intervals and use low-pressure sprays to avoid contaminating fruit.
In other areas of the United States, pheromone mating disruption has worked well for controlling this pest in crops where it is a regular problem. However, this technique has not been studied in California because peachtree borer is only an occasional problem.
Keep tree bases free of vegetation to improve spray coverage when treating for this pest, especially in the Central Valley. Also, heat and dryness reduce the survival of eggs and larvae, and keeping vegetation away from the tree bases provides a drier environment.
UC IPM Pest Management Guidelines:
Insects and Mites
J. A. Grant, UC Cooperative Extension, San Joaquin County
Acknowledgment for contributions to Insects and Mites:J. Colyn, Mid-Valley Ag. Services
M. Devencenzi, Devencenzi Ag. Pest Mgmt. and Research
P. McKenzie, Mid-Valley Ag. Services