Red-shouldered bostrichid
Xylobiops basilaris (Say)
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. Hickory, pecan, persimmon, black locust, oak, redbud,
mulberry, elm, Osage-orange, apple, ash, peach, honey-locust, pear, poison
sumac, poison ivy, eucalyptus. Hickory, pecan, and persimmon are favored
hosts, but the range is diverse, occasionally including conifers and some vines
(Beal and others 1952, Fisher 1950)
Range. Eastern half of the United States from Florida north to
New York, west to Texas and Kansas and in southeastern Canada (Fisher 1950).
Description
Adult. Brownish black to dark reddish brown beetle with basal
half of elytra reddish to brownish yellow, 3.3 to 7.0 mm long and 1.5 to 2.5 mm
wide (Beal and others 1952, Fisher 1950, Gill 1924). Wing covers taper to
oblique angle at posterior end, edges armed with three conspicuous teeth on each
side. Antennae, palpi, and tarsi brownish yellow.
Larva. Yellowish white, wrinkled, C-shaped, 5 to 6 mm
long. Small globular head with mouthparts extending forward. Thorax,
and especially prothorax, greatly enlarged with three pairs of conspicuous legs.
Pupa. Pale yellow (Lugger 1899).
Biology. Adults emerge during summer and fly in search of
suitable host trees, where they bore through the bark and into the sapwood (Gill
1924, Lugger 1899). Adult tunnels are constructed across the grain just
under the bark surface in sapwood. Tunnels may girdle limbs and trunks of
small diameter. Eggs are deposited at intervals along the sides of
tunnels. Larvae feed mostly in sapwood and to some extent in heartwood,
tunneling parallel to the grain. They spend winter in galleries, mostly as
mature larvae, but sometimes as pupae or adults. Adults often bore into
healthy twigs for food and shelter and commonly spend the fall, winter, and
spring in galleries within twigs and branches. A generation can develop in
1 year under optimum conditions, but longer periods are sometimes required.
Injury and Damage. Stressed, dying, and recently dead trees are
most susceptible to attack (Beal and others 1952, Gill 1924, Moznette and others
1931). Branches that fail to bud in spring and flagged branches having
withered and brown leaves, along with girdled and fallen branches, are good
indicators of infestation. Inspection of such branches reveals one round
entrance hole 2 to 3 mm in diameter adjacent to one or more buds or leaf
scars. Branches are easily broken at these sites because they have been
partially to completely girdled beneath the bark. Emerging beetles leave
many 2- to 3-mm round exit holes that give the appearance of shotholes (Gill
1924). Dissection of infested branches reveals numerous parallel galleries
filled with very fine, powderlike frass. The round frass-packed galleries
are most characteristic when viewed in cross section. Infested trees cut
for use as wood products can be quickly destroyed if not processed
promptly. These insects may cause some twig dieback and possibly hasten
the death of trees already stressed or dying from other causes, but the threat
to healthy trees is minimal.
Control. Natural control includes four species of hymenopterous
parasites--Bephratoides n. sp., Ecphylus flavus Marsh, Glyptodoryctes
caryae (Ashmead), Wroughtonia ferruginea (Brues), and an unidentified
dipteron (Beal and others 1952, Burks 1979, Marsh 1979). Because borers
present little threat to healthy well-kept trees, good cultural practices should
be followed to maintain tree vigor (Moznette and others 1931). Sources of
infestation can be eliminated by promptly removing and destroying all dead and
dying twigs, branches, and prunings. Any dying or dead trees to be used
for wood products should be processed promptly with assurance that boards do not
contain wane edges with bark that encourage beetle attack.
Damage cross section of riddled pecan bolts. James Solomon,
USDA Forest Service. |
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