Pigeon tremex
Tremex columba (Linnaeus)
J.D. Solomon – Research Entomologist (retired), Southern Forest Experiment Station - Southern Hardwoods Laboratory, USDA Forest Service
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. Beech, elm, hickory, maple, oak, poplar, apple, pear,
sycamore, hackberry. Prefers maple and beech, but readily attacks hickory,
elm, and oak (Blackman and Ellis 1916, Stillwell 1967). Attacks other
species less frequently.
Range. Throughout the United States and southern Canada west to
the Rocky Mountains with a few records from Utah, Arizona, and southern
California (Doane and others 1936, Ives and Wong 1988, USDA FS 1985).
Three geographic races, with race 1 common in southeastern Canada and the
northeastern United States, race 2 common in the southeastern United States
north to Pennsylvania and west to Utah, and race 3 in the Rocky Mountains.
Some overlap in range among the three races.
Description
Adult. Large, cylindrical, heavily bodied, thick-waisted,
wasplike horntail with abdomen ending in hornlike projection (Beal and others
1952, Doane and others 1936, USDA FS 1985). Horny projection of abdomen
long and spearlike; encasing ovipositor in females but short and triangular in
males. Head large, widened behind eyes. Two pairs of wing
transparent to smoky brown. Females 37 to 50 mm long; males 18 to 37 mm
long. The three geographic races differ in color: race 1, abdomen black
with brownish yellow bands and spots, head and thorax brown; race 2, abdomen
yellow with sides of eighth and ninth segments black, head and thorax yellowish
brown; race 3, brownish yellow throughout.
Egg. Dark brown to blackish, elongate, slender, straight to
slightly curved, narrow at ends, 1.0 to 1.5 mm long and about 0.2 mm in diameter
(Stillwell 1967).
Larva. Cylindrical, straight to lightly curved or slightly
S-shaped, white except for amber head, brownish mandibles; 14 to 50 mm long when
mature (Beal and others 1952, McDaniel 1936, Stillwell 1967). Head
overhung by prothoracic segment, dome shaped, smooth, and shining. Three
pairs small thoracic legs, nonsegmented, clawless. Abdomen ends in brown
sclerotized prong.
Biology. In southern range, emergence of adults begin in early
June, but in New Brunswick, emergence begins in mid-August, peaks in early
September, and continues until early October (Blackman and Ellis 1916, McDaniel
1936, Stillwell 1967, USDA FS 1985). Over most of the range, adults are
present from early summer to early fall. When ready to oviposit, females
select suitable sites on the bark and drill holes with sawlike movements of the
ovipositor. Oviposition channels are 2 to 20 mm deep in the wood and
usually at right angles to the bark surface. From two to seven eggs are
deposited at intervals, sometimes end to end in the oviposition channel as the
ovipositor is withdrawn. Eggs usually hatch in 3 to 4 weeks, but in New
Brunswick, some do not hatch until the following May or June. At
oviposition, a wood-rotting fungus--Daedalea unicolor Buller ex Fries – carried in paired intersegmental sacs near the base of the ovipositor, is deposited in the wood. Larvae feed on the fungus-softened wood and construct long,
round galleries that loop and meander through the sapwood and heartwood.
Without the fungus, eggs hatch, but larvae cannot develop beyond the first
instar. Larvae pack the frass tightly within the gallery and tunnel for 15
cm to 2 m, and occasionally up to 3 m. Female larvae also carry the
wood-rotting fungus in a hypopleural fold between the first and second abdominal segments. Pupation occurs in the galleries in the sapwood and
lasts 3 to 6 weeks. The new adults tunnel their way to the surface and
emerge. In Michigan and New Brunswick, a generation requires 2 years, but
in the southern range apparently only 1 year.
Injury and Damage. This pest usually attacks trees weakened or
dying from disease, other insects, fire, flooding, or other causes; it
occasionally attacks healthy trees, especially injured ones (Beal and others
1952, Blackman and Ellis 1916, Stillwell 1967). In the early stages,
infestations present little or no evidence of entrance holes and ejected frass.
However, it is common in the summer and fall to observe adult females
ovipositing on susceptible tree trunks. Dead female with their
ovipositiors firmly wedged in the wood can sometimes be found, especially on
living trees that have green or sappy wood. Dissecting infested stems can
reveal frass-packed, meandering, larval galleries and the empty adult exit
tunnels that curve in a sweep to the surface. From the exterior, the exit
holes are circular and 7 to 8 mm in diameter. Exit holes are typically
clustered in localized parts of stems. Because the insect prefers weakened
trees, it is not an important pest. However, it can cause economically
damaging losses in dying timber and salvage operations.
Control. Four species of hymenopterous parasites--Ibalia
maculipennis Haldeman, Megarhyssa atrata (Fabricius), M. greeni
Viereck, and M. macrurus (Linneaus)--destroy up to 40% of the
larvae and pupae (Burks 1979, Carlson 1979, Stillwell 1967). Woodpeckers,
especially the pileated woodpecker and hairy woodpecker, are effective
predators, but unfortunately they destroy many of the parasites as well.
Infestations can be avoided by keeping trees healthy and vigorous. Tree
injuries should be promptly dressed and filled to discourage oviposition.
[ Contents ]
[ Previous ]
[ Next ]
[ Home ]
|
