How to Manage Pests

Pests in Gardens and Landscapes

Pest identification and confirmation—Borers

The four major boring insects that damage trunks and limbs of deciduous fruit or nut trees are the Pacific flatheaded borer, the peachtree borer, the shothole borer, and the American plum borer. The adult Pacific flatheaded borer is a hard, dark, mottled beetle with a bronzy cast. Larvae have a distinctive flattened enlargement just behind the head. Shothole borers are tiny black beetles; larvae are tiny grubs that curl into a C shape. Both beetles attack trees that have been previously injured or weakened by sunburn or other causes. Peachtree borers bore into undamaged trunks of young trees.They are a problem on stone fruits but not other fruit or nut trees. Damage may be primarily in the crown area or lower part of the trunk or just below the soil line. The adult is a steel blue to black moth. Larvae are light brown or pinkish with a darker head. American plum borer larvae are white with a darker head. Adults are gray moths with brown and black markings. Larvae bore into the tree leaving reddish orange frass.

Flatheaded larva
Flatheaded larva

Flatheaded adult
Flatheaded adult

Peachtree borer larva
Peachtree borer larva

Peachtree borer adult
Peachtree borer adult

Amer. plum larva
Amer. plum larva

Amer. plum adult
Amer. plum adult

Shothole borer adult
Shothole borer adult


Statewide IPM Program, Agriculture and Natural Resources, University of California
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