Azalea Stem Borer – Oberea myops

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Azalea Stem Borer (Oberea myops)

Latin Name: Oberea myops

Common Name: Azalea Stem Borer

Appearance:

The azalea stem borer is a beetle known as the rhododendron stem borer and Blueberry stem borer. It belongs to the Cerambycidae [long-horned borers] family and has a life cycle of two to three years.

  • It spends the winter as a larva, generally burrowing down in the plant, which may be an adaptation for better winter survival.
  • The completely grown larva is yellowish, measuring around 25 mm (1 inch) in length and 3 mm (1/8 inch) in width.
  • The adult is around 14-16mm long (just over 12 inches). An adult beetle’s head, pronotum, and abdomen are all pale orange-brown, but the wing coverings are dark grey.
  • The raspberry cane borer, a close cousin of the beetle, is virtually identical.

Host plants:

Host plants include blueberry, rhododendron, azalea, and mountain laurel.

Territory: The azalea stem borer is found throughout the eastern United States

Damage caused by Azalea Stem Borer:

Azalea, rhododendron, blueberry, and mountain laurel are all infested by azalea stem borers. As the larvae delve lower into the twigs, they wilt and die. Symptoms may mirror those of aerial phytophthora blight at this stage. Infested stems typically fall off at the base later in the season, leaving the plant uneven and ugly. Small plants may entirely snap off.

Life history and Habits:

From mid-May through June, adult azalea stem borers emerge. Eggs are put under the bark between two rows of holes approximately a half-inch apart, eaten through the bark. The larva hatches and bores its way down the twig, through the stem, and finally to the plant’s crown. The base of the stem is severely compromised. The larvae then burrow deep into the roots and spend the winter there. Frass, which resembles coarse sawdust, is discharged from pores in the stem’s bark near the plant’s base. As the larva bores downward into the twigs, they wilt. The larvae pupate in the following year’s spring, or two to three years later.