Sassafras Borer
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Hosts
Sassafras, spicebush. Sassafras is preferred (Champlain and others 1925). Adults have been collected on sumac, but this is not likely a larval host (Mutchler and Weiss 1923).
Range
Throughout the eastern United States, from Pennsylvania south to Georgia and west to Arkansas and Michigan, and in Ontario (Champlain and others 1925, Fattig 1947, Gosling and Gosling 1977, Hicks 1962).
Description
Adult
Large, elongate, slender longhorn beetle measuring about 17 mm long an 3.8 mm wide (Beal and others 1952, Knull 1946). Dark brown antennae extend beyond tips of elytra in males but do not reach tips in females. Head, prothorax, ventral surfaces, and legs brownish yellow (Knull 1946) to brick red (Beal and others 1952). Elytra covered with gray pubescence on black ground color. Pronotum broader than long, constricted in front and rear, with one median and two lateral callosites. Elytra elongate with tips truncated and surfaces faintly ridged longitudinally and densely and coarsely punctate.
Larva
Mature larva very elongate, slender, cylindrical, smooth, shiny, and sparsely covered with short, yellowish brown hairs (Craighead 1923). Head brown and remainder of body pale yellow. Larvae legless, body segments gradually decrease in width from front to rear; 16 to 26 mm long.
Pupa
Yellowish with darker eyes, mouthparts and wingpads; 15 to 18 mm long.
Biology
Adults emerge from late June to early August in Michigan (Gosling and Gosling 1977), during May and June in North Carolina (Beal and others 1952), from late April to early June in Mississippi. Females deposit eggs singly in niches chewed in the bark of terminals and near the tips of small branches. The egg niche is made between a double row of punctures chewed by the female, which ring the stem, girdling it and killing the shoot (Beal and others 1952). Larvae feed downward, enter the main stem, and eventually bore into the base of the stem and the larger roots. Galleries are made in the wood (center of small stems) and may be 1 m or longer, but gallery lengths of 60 to 90 cm are most common. While tunneling in the stem, larvae periodically bore short galleries at right angles to the main gallery and through to the bark surface to eject frass (Craighead 1923). They pupate in early to mid-April in the South in the gallery near ground level. Emerging adults chew exit holes directly through the bark. In the North, this borer requires 2 to 3 years to complete the life cycle (Craighead 1923). In the Piedmont of North Carolina, one generation per year has been reported (Beal and others 1952), whereas, in Mississippi, larvae of two sizes are commonly found, indicating a 2-year life cycle.
Injury and Damage
The first evidence of infestation is wilting foliage on the terminal and branch tips (Craighead 1923, Beal and others 1952). Closer examination of the twig just below the wilt reveals a double ring of punctures around the stem with an egg niche between. As larval boring progresses toward and down the main stem, small holes may be present at regular intervals in the bark, through which frass is extruded. The frass consists mostly of short, cylindrical, excrement pellets, grayish yellow to light brown, and adhering end to end in strands up to 10 mm long. By the end of the second season of an attack, the entire young plant may be dead from extensive mining at the base of the main stem and in the larger roots. Young living sassafras trees from 6.3 to 51.0 mm in diameter are susceptible to attack. Adults leave irregular oval exit holes roughly 3 mm by 4 mm in the bark. Young plants, primarily large seedlings and young saplings, may be tunneled and frequently girdled and killed. Young growth in old fields and field borders has suffered most from infestation. This borer has commonly caused extensive mortality of young sassafras trees on the Piedmont of North Carolina and on similar sites in other states in the South (Beal and other 1952).
Control
Woodpeckers capture small numbers of larvae and pupae as indicated by excavation holes extending into the larval galleries. Direct controls are rarely needed except in ornamentals. Newly infested terminals and branches should be pruned just below the wilted and girdled sites and burned to destroy the young larvae.
Gallery
 Photo by James Solomon, USDA Forest Service, Bugwood.org |  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.
