Sassafras borer
Oberea ruficollis (Fabricius)
From: 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.
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.
Larva(e) in gallery. James Solomon,
USDA Forest Service. |
Adult(s). James Solomon,
USDA Forest Service. |
Damage girdle & oviposition site in middle of girdled spot. James Solomon,
USDA Forest Service. |
[ Contents ]
[ Previous ]
[ Next ]
[ Home ]
|
