Goldenrod Borer
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Hosts
Baccharis, goldenrod. Goldenrod is mentioned as the host in early reports, but recent unpublished findings suggest that baccharis, especially eastern baccharis, is a common host (Barnes and Lindsey 1921, Bennett 1963, Cashatt 1972, Kimball 1965).
Range
Like the closely related O. balanotes, primarily an eastern species reported from Massachusetts and New York south to southern Florida and west to Colorado and Utah (Barnes and Lindsey 1921, Cashatt 1972). Also recorded from Quebec (Forbes 1923).
Description
Adult
Slender-bodied moth with long legs, narrow wings, and cream colored with slightly darker brown markings (Cashatt 1972, Fernald 1898). Forewing brownish white with indistinct brown dash extending from base, which fades out toward cleft. Hindwings uniformly brownish white with silky luster. Wingspan ranges from 14 to 29 mm. Body light brownish white dusted with brown scales. Distinguished from other stem-boring pterophorids by its smallness and distinct spot at base of wing cleft.
Larva
Creamy white and light brown, and 12 to 18 mm long. Head, thoracic shield, and dorsum of caudal four or five abdominal segments brown. Abdomen terminates into a dark brown anal plate with two pronglike processes and long hairs.
Pupa
Long (10 to 15 mm) and slender, light brown.
Biology
Moths emerge during most months, depending on latitude (Cashatt 1972, Kimball 1965). Although most specimens have been collected during June and July, emergence has occurred as early as February in Florida and as late as October in New York. In goldenrod, larvae initially bore into branches (Fernald 1898), but by mid-September they abandon the branches, move down the plant and bore into the main stem a few centimeters above the groundline. Here, larvae bore downward into the roots, where they overwinter. During spring, larvae work their way back to the aboveground entrances, enlarge the galleries, plug openings loosely with frass and debris, and pupate in the galleries. Empty fresh galleries in main stems of baccharis have been found during fall, indicating the possibility of larval movement. Galleries in baccharis are long and cylindrical, similar to those made by O. balanotes, but slightly smaller. This borer has one generation per year.
Injury and Damage
New attack sites in baccharis can be recognized by sap oozing from the bark and fine yellowish brown frass in bark crevices. Frass becomes course granular and is often clumped at round gallery entrances. Long, slender galleries are just beneath the wood surface. Larvae tunnel in the main stem and branches, sometimes causing breakage of host parts.
Control
Nothing is known of natural enemies, and direct controls have not been needed.
References
Solomon, J.D. 1995. Guide to insect borers of North American broadleaf trees and shrubs. Argic. Handbk. 706. Washington, DC: U.S. Department of Agriculture, Forest Service. 735 p.
