Adult weevils are attracted by the odor of fresh pine resin, and quickly invade logging areas. Eggs are laid in lateral roots of fresh pine stumps, where they hatch in approximately five to ten days. Larvae feed on the inner-bark tissues of roots. At maturity, larvae usually construct a chip cocoon in a chamber cut into the wood, and pupate in the cocoon. On emerging, adults feed on the tender bark of seedlings, or twigs of trees. The small irregular feeding patches in the bark are characteristic of weevil damage. Heavy feeding girdles the stem or twig, causing wilting and eventual death. Newly emerged adult females feed for approximately one month before laying eggs. Females may lay eggs sporadically through two growing seasons. The average female lays about 50 eggs in her lifetime. In the South there are two peaks in adult weevil population each year; the first occurs in the early spring (March-May) followed by a second somewhat lower peak in July and August.
This insect can be controlled by delaying planting in cut-over areas for at least nine months, or by treating seedlings with a suitable insecticide.
Adult pales weevil feeding on seedling.
WHITE PINE WEEVIL, Pissodes strobi (Peck)
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.
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.