Hosts: Balsam fir, spruces and white pine
Evidence: The damage of most concern to urban trees is that caused when the adult beetles (a) feed on bark on the underside of twigs, causing the tips to die and turn red (b). Look for a wound at the base of the dead shoot (c). Otherwise, the beetle is usually considered a secondary pest, attacking the trunks of weakened, dying or dead trees. Small piles of sawdust may be present near the base of trees where larvae have been tunneling.
Life Cycle: There is a one or two year life cycle. Adults emerge through circular exit holes in the wood and are present during the summer. They feed on tender bark of twigs, causing tips to flag. Eggs are laid in the bark crevices of weak, recently-killed or newly-cut trees. When eggs hatch, young larvae bore a tunnel through the phloem into the cambium. Young larvae mine beneath the bark. Later instars tunnel toward the heartwood. Prior to pupation, the larva turns its tunnel toward the surface, where it pupates behind a chip plug.
Management: Reducing the presence of dead and dying trees in the vicinity of ornamental conifers can help reduce the numbers of whitespotted sawyer beetle adults in an area, and therefore reduce the amount of damage caused by adult feeding on the bark of twigs. Logs that have been cut can be debarked or put out in the sun to reduce the availability of egg-laying sites.
Similar Species: The northeastern sawyer, Monochamus notatus (Drury), is a larger gray species which commonly infests stressed or dying white pine, especially those affected by lightning strikes.
Figure a: E. Bradford Walker, Vermont Department of Forests, Parks and Recreation, Waterbury, VT.
Figure b: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Figure c: Ronald S. Kelley, Vermont Department of Forests, Parks and Recreation, Morrisville, VT.
Drooz, A.T. 1985. Insects of Eastern Forests. USDA Forest Service Miscellaneous Publication 1426. p 313-314;
Martineau, R. 1984. Insects Harmful to Forest Trees . Agriculture Canada Government Publishing Centre, Supply and Services, Ottawa. p 100-102;
Rose, A.H. and Lindquist, O.H. Revised by Syme, P. 1994. Insects of Eastern Spruces, Fir and Hemlock. Canadian Forest Service Publication. p 112-114.