The white pine weevil is generally regarded as the most serious insect
pest of white pine. Although it usually does not cause mortality, trees
suffering repeated attacks become stunted and deformed to the point of
being commercially unusable. The weevil has become such a problem in
some areas that it prohibits the growing of white pine. In addition to
eastern white pine, the white pine weevils also attack Norway spruce and
jack pine. Other pines and spruces are attacked to a lesser degree. The
weevil is found throughout the range of eastern white pine.
[Illustration: Pine leader damaged by the white pine weevil.]
During the latter half of April, the adults may be found on the terminal
shoots of host trees where the female lays her eggs. Up to 200 eggs are
deposited over a six-week period. The eggs are laid in feeding punctures
in the bark, and hatch about two weeks later. Characteristically, the
young larvae position themselves around the shoot and begin feeding as a
group down the terminal through the inner bark. Small holes scattered
over the bark are characteristic of white pine weevil attacks. After
five or six weeks the larvae construct pupal chambers in the pith or
wood of the terminal shoot and transform into adults. The young adults
remain in the dead terminal until late October and November when they
move to favorable overwintering sites on the ground, usually at the base
of the host tree.
Control of the white pine weevil is difficult. It is possible, however,
to reduce the damage by making conditions in a young stand unfavorable
for egg laying. This is possible because the female weevil will only lay
eggs within a rather narrow range of temperature and relative humidity.
Various techniques involving the use of shade from “nurse trees” have
been developed but require intensive management. Under certain
circumstances, chemical control can be used.