Solomon, J.D. 1995. Guide to Insect Borers in North American Broadleaf Trees and Shrubs. Agriculture Handbook 706. Washington, DC. United States Department of Agriculture, Forest Service. 735 p.
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.
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.
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.
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).
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.
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.
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.