Oak stem borer
Aneflomorpha subpubescens (LeConte)
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. Oak, chestnut. White oak preferred but black,
southern red, blackjack, post, willow, and water oaks have also been listed as
hosts (Beal and others 1952).
Range. Eastern United States from Pennsylvania south to Florida
and west to Oklahoma (Linsley 1963). Collected most often in the
Appalachian Mountains from Georgia northward.
Description
Adult. Very narrow, extremely elongate longhorn beetle, 15 to 18
mm long and only about 3 mm wide (Knull 1946, Linsley 1963). Beetles
generally light brown to reddish brown with semierect brown pubescence.
Tips of elytra notched and bispinose. Antennae slightly shorter than body
in females, slightly longer than body in males, and equipped with single short
spines on third and fourth segments.
Larva. Very slender and cylindrical, with body thickly covered
with fine, white setae that become golden on thorax. Grown larvae
yellowish except for light brown mandibles and tergal plates; up to 18 mm long.
Pupa. Head and thorax glabrous; posterior half of abdomen has
prominent spines.
Biology. Adults emerge late May through July and deposit eggs at
leaf bases, mostly on small twigs near the tops of seedlings and sprouts (Knull
1946, Linsley 1963, USDA FS 1985). Newly hatched larvae burrow into the
twig and tunnel within the branch toward the main stem. Larvae make tiny
round holes in a straight line to eject frass. As the larvae grow, they
consume and hollow out the woody part of the stem, often cutting the stem off or
causing it to break off in sections. During late summer and fall, larvae
typically make their way to the base of the plant and enter the root collar and
upper roots to overwitner. They usually cut off the main stem just above
groundlines and plug the open gallery tightly with fibrous frass. During
spring, they prepare pupal chambers between two wads of frass within the gallery
and pupate (Champlain and others 1925). New adults chew through the upper
wad of frass to emerge. There is one generation per year (Beal and others
1952, Craighead 1923).
Injury and Damage. Attacks usually begin in a small branch near
the top of the plant but sometimes in a small twig on a side branch.
Seedlings and sprouts 20 to 70 cm tall and 6 to 25 mm in diameter at the root
collar seem most susceptible. Larvae tunnel in the twig down to the main
stem or trunk and then to the root collar or below. Examination reveals a
single straight row of small round holes 3 to 6 mm apart along the branch or
twig and down the main stem to the groundline. Frass is extruded through
these holes and can be found in small piles at or near the base of the
plant. Larvae hollow the stem, sometimes cutting or girdling portions so
that sections break. A stem may be completely hollowed, leaving only a
shell. Browning foliage and dying terminals, branches, or entirely dead
seedlings are quite noticeable during the growing season. Dying leaves
remain attached to the plant as flags of continuing infestation.
Occasionally, this borer becomes abundant and kills a high proportion of the oak
regeneration in parts of the Southeast (USDA FS 1985).
Control. Little is known of natural enemies. Some evidence
of woodpecker predation has been observed. No direct controls have been
investigated.
Larva(e) and damage to red oak (figure 165 e in USDA Forest Service Ag. Handbook AH-706, 1995). James Solomon,
USDA Forest Service. |
Damage to seedling and sprouts. James Solomon,
USDA Forest Service. |
Damage series of holes made in oak seedling. James Solomon,
USDA Forest Service. |
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