AZALEA
STEM BORER
CAUTION: This information was developed for North Carolina and may not apply to other areas.
Azalea stem borers (aka rhododendron stem borer and blueberry stem borer) are slender long-horned beetles about 1/2 to 5/8 inch
long with yellowish brown heads and thoraxes. The wing covers are yellowish
gray with dark outer margins, and there are 2 black spots on the thorax.
The egg has been described as "yellow". The eggs occur under the bark.
The
azalea stem borer is a slender, yellow, legless grub found inside the stem.
No description is available for the pupa.
Adult azalea stem borers emerge from mid-May through June. Eggs are inserted under the bark between two rows of holes chewed through the bark about 1/2 inch apart.
The larva hatches and bores down the twig into the stem and eventually all the way to the crown of the plant.
The stem is greatly weakened at the base. The larvae then bore down into
the roots where thy spend the winter. Coarse sawdustlike frass is expelled
through holes in the bark of the stem and at the base of the plant. Infested
twigs wilt as the larva bores downward inside. The larvae pupate the following
spring.
Cutting off and burning infested stems as soon as they are noticed in the growing season is recommended for control. If shrubs have been reinfested year after year, it may be helpful to protect the plants with a pyrethroid insecticide such as permethrin or cyfluthrin. This should give adequate control if applied in spring after the new growth has emerged and hardened off somewhat in mid-May and again in early June. Consult the North Carolina Agricultural Chemicals Manual for specific recommendations. Look in the Trees and Woody Ornamentals section, under "Any Plant: Borers". Be sure to read and follow all label instructions.
Helpful Link: Arthropod Pests of Azalea
Published by North Carolina Cooperative Extension Service
Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.
