Chestnut timberworm
Melittomma sericeum (Harris)
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. Chestnut, oak. American chestnut, before its
demise, was the preferred host (Hopkins 1894); now found chiefly in white oak
(USDA FS 1985).
Range. An eastern species, range corresponds closely with that
of American chestnut in the eastern United States (Snyder 1927).
Description
Adult. Slender, elongate, chestnut brown beetle with deflexed
head, clothed with fine, silky hair, 11 to 15 mm long (Herrick 1935, USDA FS
1985).
Larva. White to yellowish brown, smooth, elongate, and
cylindrical with a large, yellow, rounded head partially covered by enlarged
hood-shaped tergum of prothorax (Peterson 1960). Ninth abdominal segment
enlarged and conspicuously armed with dark brown scooplike structure bearing
many toothlike spines. Full-grown larvae 15 to 18 mm long.
Biology. Adults deposit eggs in cracks and crevices on the
surface of wood, often at wounded sites (Hopkins 1894, USDA FS 1985).
Young larvae bore directly into wood, forming tiny holes that are scarcely
visible. As larvae grow, galleries are enlarged and extended for many
centimeters through the sapwood and heartwood. Pupation occurs in cells
constructed near the surface. New adults chew circular exit holes.
The life cycle has not been established, but a generation probably requires
several years.
Injury and Damage. Fine powdery frass may be found at tiny holes
that initially are barely visible. Attack sites are found in both sapwood
and heartwood and most often are associated with wounds and broken or decayed
branches (Herrick 1935, Hopkins 1894); dying trees, stumps, and fresh-cut logs
are also attacked. Holes in lumber are generally unstained or only
slightly stained, round, and vary from 0.3 to 6.4 mm in diameter (Snyder
1927). Most American chestnut was killed by the mid-1900's by chestnut
blight, a disease introduced from the Orient in the early 1900's (Clapper and
Gravatt 1943). Diseased and dying trees were riddled by chestnut
timberworms. Nearly every tree of merchantable size contained some
injury. Lumber from such trees was downgraded to "sound wormy,"
resulting in sizeable losses. Today, affected lumber is considered
character marked and sold as "wormy chestnut" for decorative purposes
at handsome prices.
Control. Minimizing wounds from harvesting equipment, stand
improvement work, wildfire, and other insect borers can help to reduce
infestations and losses (Craighead 1950).
Damage wormy chestnut lumber. James Solomon,
USDA Forest Service. |
Damage wormy chestnut lumber - close-up. James Solomon,
USDA Forest Service. |
Damage dead chestnut and live sprouts. James Solomon,
USDA Forest Service. |
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