White pine weevil damage on conifers is causing wilted leaders
White pine weevils are damaging conifers in Christmas tree fields and landscapes, causing the current year's growth on the leader to wilt, droop and eventually die.
Wilted leaders of many conifers that have been attacked by white pine weevil are beginning to show up in Christmas tree fields as well as landscapes. Larvae of the white pine weevil kill the terminal leader and the top two to four years of growth on many varieties of spruce, as well as white and Scotch pine trees. Typically in the first part of July, terminal leaders develop the characteristic drooping and curled new growth and eventually die.
Typical damage to spruce leader from white pine weevil.
Photo credit: Dave Powell, USDA Forest Serv., Bugwood.org.
White pine weevil larvae.
To confirm white pine weevil injury, use your fingernail and pull the bark away from the leader. If it’s weevil damage, you will see the frass, small white, legless larvae and maybe some chip cocoons just below the bark. These leaders should be pruned out when the first symptoms appear. Cut the terminal leader off an inch or two below the area damaged by the weevils. When you prune out the infested leader, make sure not to leave the cut terminals lying in the field because the larvae will continue to develop. After the dead leader is removed, select a healthy lateral shoot on the uppermost whorl to become the new leader. Trim the rest of the shoots back to one-half of their original length. This will enable the tree to recover its apical dominance and good form faster. Damage from white pine weevil can be prevented by spraying the upper terminals of spruce and pine next year in early to mid-April and again two weeks later.