Apricot-Peachtree borer

Synanthedon exitiosa

Pest description and crop damage Adult male is a steel-blue, clear-winged moth, the female is similar in appearance but has smoky-colored wings and an orange band around her abdomen. Both male and female moths are approximately 1 inch in length, with males slightly smaller than females. Adult flight is usually from late June through September and eggs are laid at or on the base of the fruit tree. Larvae burrow in the crown and roots, girdle young trees, and weaken others. A single larva is capable of girdling a newly-planted fruit tree. Full-grown larvae are 1 to 1.5 inch long with a whitish body and a brown head.

Biology and life history The borer overwinters as a larva under the tree bark, usually below the soil surface. As temperatures rise above 50°F in the spring, larvae resume feeding on the tissues under the bark. Reaching maturity during May through June, the larvae pupate. Adult moths emerge beginning in June and continue to emerge through September. Eggs are laid quickly after mating. The young larvae hatch after 8 to 10 days and bore immediately into the base of the tree. Larvae in the bark above the soil surface usually do not survive the winter in cold areas.

Pest monitoring In late fall or early spring, scout for signs of borer infestation and larval feeding near the base of the tree trunk near the soil surface. Larval presence can best be detected by globs of gum/sap mixed with a granular brown frass that appear at the base of infested fruit trees.

Management-cultural control

Protect the base of the fruit tree from larval entry by placing a plastic or metal cone or barrier around it before egg laying begins. The cone should be pushed 1 to 2 inches into the soil and should fit snugly around the trunk at the top to prevent the tiny larvae from getting beneath it. Alternatively, if there are only one or a few apricot trees in a home orchard, it is quicker and cheaper to control this insect by "worming." Use a pocket knife, wire or some pointed instrument to remove dirt around the tree and dig out the larvae.

Management-chemical control

Spray applications and, more importantly, pesticide residues on the trunk of the tree can prevent newly-hatched larvae from boring beneath the tree bark and entering the woody trunk where they are protected from all insecticide sprays.

Management-chemical control: HOME USE

  • azadirachtin-Some formulations are OMRI-listed for organic use.
  • kaolin-When sprayed on leaves, trunks, and fruit, kaolin acts as a repellant to some insects. Some formulations are OMRI-listed for organic use.
  • lambda-cyhalothrin-Highly toxic to bees.
  • pyrethrins-Highly toxic to bees. Some formulations are OMRI-listed for organic use.
  • zeta-cypermethrin-Highly toxic to bees.

Management-chemical control: COMMERCIAL USE

Spring and summer sprays

  • esfenvalerate (Asana XL) at 2 to 5.8 fl oz/100 gal water of dilute spray (4.8 to 14.5 fl oz/A of concentrate). REI 12 hr. PHI 14 days. Extremely toxic to fish and aquatic invertebrates; avoid spray drift and runoff to surface waters. Do not spray more than 0.375 lb/A per season, with no more than 0.3 lb/A between bloom and harvest.
  • Isomate (Isomate PTB) at 100 dispensers/A (0.51 fl oz ai/A). Place prior to moth emergence in the spring. These dispensers release a synthetic insect pheromone that disrupts insect mating. Dispensers must be placed in the orchard before adult mating and egg-laying flight begins in late June or when the first moths are captured in pheromone traps. Careful scouting and monitoring are necessary to use this product effectively.