Riley
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.
Hosts
Maple, boxelder. Silver maple, boxelder, sugar maple, and bigleaf maple have been listed specifically. Other maple species are probably hosts (Craighead 1950, Powell 1962).
Range
Transcontinental in distribution across the northern United States and south to Mississippi (Furniss and Carolin 1977, Powell 1962). Discontinuously distributed across Canada, from Nova Scotia to southern Alberta (Prentice 1965).
Description
Adult
Small grayish moth with wingspan of 11 to 18 mm (Heinrich 1923). Forewings dark olive green mottled with yellow and gray and sometimes small indistinct black markings (Forbes 1923, Miller 1987).
Larva
Pale white to gray, stout, and about 10 mm long when mature. Yellow-brown head somewhat wider than long, averaging 1.1 mm wide, with mouthparts directed forward. Thoracic shield yellow brown, often darker laterally and posteriorly. Spinules on integument moderately dense and dark (MacKay 1959). Poorly developed anal fork with 4 to 6 teeth. (MacKay 1959, Powell 1962).
Biology
Moths fly from April to October in the northern United States (Miller 1987). Moths have been collected in California as early as February and as late as September, suggesting that this species is multivoltine in the San Francisco Bay area (Powell 1962). Behavior is similar to that of P. arizonae in California, except that larval tunnels are somewhat longer (40 to 46 mm) and that they normally pupate outside of the tunnels, presumably in leaf litter.
Injury and Damage
Larvae hollow out dormant buds and seeds in fall and continue to feed on dormant buds in spring (MacAloney and Ewan 1964). During the growing season, larvae bore in the current year's shoots, often killing them and preventing terminal growth. Frass, which is ejected from the galleries, is mixed with webbing to form shelters around the entrances. When terminals are killed, opposite lateral shoots begin elongating and often produce forks or other deformities. Larval entrance holes are typically present near the base of current season's growth. When an infesation is sufficiently severe, trees become bushy and disfigured (MacAloney and Ewan 1964). Large trees have been so heavily injured in early summer in West Virginia that they appeared to have been damaged by heavy frost. In the Pacific Northwest, 7 to 50% of bigleaf maple seeds have been destroyed by this borer. Boxelders planted in nurseries and shelterbelts and as ornamentals are often heavily infested in the northern Great Plains, as is sugar maple in the northern Great Lakes area (MacAloney and Ewan 1964).
Control
Two species of hymenopoterous parasites--Elachertus proteoteralis Howard and Scambus pterophori (Ashmead)--have been recorded (Burks 1979, Carlson 1979). Removing and destroying infested twigs in fall or spring, combined with foliar applications of residual-type insecticides when moths are active, should help to prevent and reduce infestation of high-value trees.
