Shothole borer

Insect

Shothole borer

Scolytus rugulosus (Müller)

Coleoptera: Scolytidae

Distribution: Most fruit-growing states and provinces in eastern North America.

Photos

When the insects are abundant, fruit clusters wilt and associated leaves become brown. Arthur Agnello, Cornell Univ.
D

The adult is stocky with a hard black body (A) and antennae, leg segments and tips of elytra reddish brown; its head is not visible from above. The larva is a legless grub, pinkish white, and slightly enlarged just behind the reddish head (B).

Crops Affected: apples, cherries, peaches, pears, plums

Damage

Attacks all deciduous fruit trees; normally found in dead or dying wood, but can be attracted to living trees that are in a somewhat unhealthy condition. Adult produces small (1 mm) holes through the bark on the twigs of fruit trees (C), especially above a bud or other projection. Holes are sometimes indicated by sawdust or borings on the bark. On stone fruits, the holes are usually covered and sealed in by dried droplets of gum, which resemble tear drops. The female constructs an egg gallery about 2.5 cm long under the bark, parallel with the grain. Larvae are present year-round inside branches. When the insects are abundant, fruit clusters become wilted, and associated leaves become brown (D), resembling a fire blight infection.

Management

Remove all piles of wood with bark from adjacent area; destroy any damaged or dying limbs. An insecticide can be applied against adults when active, but is rarely required.

Similar Species

Peach bark beetle (Phloeotribus liminaris), which has a brown body with yellow hairs.