Baccharis Borer
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Hosts
Baccharis, bayberry. Baccharis and bayberry groups reported as hosts (Cashatt 1972, Forbes 1923); recent unpublished findings suggest that eastern baccharis is a major host.
Range
Primarily a southeastern species, found from southern Florida north to Maryland and New Jersey and west to Texas and Arizona (Barnes and Lindsey 1921, Cashatt 1972, Forbes 1923, Kimball 1965).
Description
Adult
Largest of stemboring pterophorids, slender-bodied moth with long legs and narrow wings (Barnes and Lindsey 1921, Cashatt 1972, Meyrick 1908). Forewings cleft and brownish white with dark spots at vein tips and indistinct brown dash line extending from base to near cleft. Hindwings pale brown. Wingspan varies from 30 to 42 mm. Light brown to brownish white or tan with indistinctly striped abdomen, whitish antennae, and pale brown legs.
Egg
Yellowish white, oval, and about 0.54 by 0.33 mm.
Larva
Creamy white with brown markings and 18 to 25 mm long when mature. Head dark brown around the mouthparts, with light brown mottling elsewhere. Thoracic shield with brown granulations. Anal plate brown and hardened with two prominent prongs and ringed with long hairs. Crotches in uniordinal semicircle.
Pupa
Slender, tannish brown, and 16 to 22 mm long.
Biology
Adults emerge every month, depending on location (Barnes and Lindsey 1921, Cashatt 1972). In Florida, moths have been found during all months, but mostly in late winter and spring. Emergence is recorded during July and August in Maryland, August in Arizona, July and October in South Carolina, and from June to November in Texas; reared entirely during September in Mississippi. Most deposit eggs on the bark of hosts. Larvae enter the bark and make long, narrow, nearly straight galleries in wood. Most attacks occur in the main stem and less frequently in branches. Entrance holes have been found from just above the groundline to 1.5 m. Larval galleries always enter bark and wood at an oblique angle, and nearly always extend downward into the roots, sometimes as much as 10 cm below ground. Although the galleries are in the xylem, they are usually only a few millimeters beneath the wood surface. Completed galleries range from 15 to 23 cm long and 4 to 5 mm in diameter. Pupation occurs freely within the gallery for 16 to 19 days, without a pupation chamber. Empty pupal skins at various locations in galleries indicate that moths eclose from the pupae within galleries, unlike many other woodboring Lepidoptera in which the pupae move to the exit holes for adult emergence. There appears to be one generation per year, with considerable overlapping of broods in some areas.
Injury and Damage
The earliest evidence of attack is sap-stained spots, often mixed with fine frass on bark. Later, round to oval entrance holes 2 to 4 mm in diameter, often with yellowish white frass adhering to bark below entrances, become noticeable. Dissection of infested stems reveals the long cylindrical nearly straight galleries and sometimes tunneling larvae. Bark occasionally cracks open along shallow galleries and forms long bark scars that show evidence of previous infestation. Small stems, particularly branches, sometimes break at injured sites. Heavy infestations have been found recently in thickets of eastern baccharis near Jackson, Mississippi.
Control
Ichneumonid parasites--Telelucha sp.-- have been reared from specimens in Mississippi, but rates of parasitism have been low. Direct controls have not been low. Direct controls have not been needed. This borer is being studied by Australian scientists as a possible biocontrol agent for weed Baccharis spp. in pastures.
Gallery
 Photo by James Solomon, USDA Forest Service, Bugwood.org |
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.
