White Pine Weevil Damage

The white pine weevil is considered the most destructive insect pest of eastern white pine in North America. This species kills the terminal leader primarily of eastern white pine. Colorado blue spruce, Norway spruce, Scots, red, pitch, jack, and Austrian pines, and occasionally Douglas fir are also attacked. Trees become susceptible to injury when they reach a height of about three feet. The white pine weevil prefers to attack trees exposed to direct sunlight. The first symptom evident from attack by the white pine weevil is glistening droplets of resin on terminal leaders in late March and April. This is the result of punctures made by adults in the process of feeding and cutting egg-laying sites. Injury to eastern white pine and spruce is usually confined to the previous year’s terminal leader. Damage on Scots pine often extends downward through two or three year’s growth. Infested trees are seldom killed. Most damage is done by the larval stage. Larvae are found just under the bark of infested terminals from May through July. Larvae chew and burrow completely around the stem causing the current year’s growth to wilt, droop, and eventually die, forming a “shepherd’s crook.”. One or more side branches may then bend upward to take over as the terminal leader. At this point the tree is now permanently crooked. For several years after successful attack by this pest, a few more laterals may grow as leaders. This condition may result in a forked tree. No spray treatments are effective. Instead, sanitation pruning below the shepherd’s crook and removal of the larvae-infested stem is effective. Later, additional pruning can remove all but the dominant leader.