Peachtree Borer

Peachtree borer eggs are laid during the summer on the bark at the base of trees. Larvae overwinter in the tree trunk near the soil line. They feed in the crown area and burrow up into the tree. At maturity, a larva is about 1-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 clearwinged moths with a 1-inch wing span.

(View photos of borer damage)

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 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 infested trees that you find, and return the following spring to apply insecticide by spraying the trunk from the scaffold to the soil line.

• Remove suckers and pull soil away from the base of the tree before insecticide application.
• 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.
• 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.

You can use pheromone traps to monitor adult emergence. They are useful for determining the presence of peachtree borers. The pheromone lure may be listed as peachtree borer or greater peachtree borer, but do not use lesser peachtree borer lures. Be sure to properly identify the moths that are trapped; other clearwing moths, the strawberry crown borer for example, may be attracted by the peachtree borer pheromone. For higher peachtree borer numbers, pheromone bucket traps work better than other pheromone traps.

1. Place the traps in trees before the end of April at 3 feet or lower, hanging freely within the canopy.
2. Maintain them through September, changing lures at the recommended interval (usually one month) and the trap bottoms when they become dirty and lose stickiness.
3. If they catch large numbers of male peachtree borers (approximately 5 to 10 or more per week), apply a trunk-applied insecticide utilizing the technique described above.
4. Return later and examine the trees carefully for signs of feeding activity.

Pheromone mating disruption has been successfully used in other states but is not currently registered in California.

Keep tree bases free of vegetation to help reduce problems with peachtree borer, especially in the Central Valley. Heat and dryness reduce the survival of eggs and larvae.

• Photos of borer damage