Clipping infested galls or terminal leaders
Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.
In spruce trees, galls are forming on Colorado blue spruce trees. If you have just a few trees with a few galls, you can clip these galls off and destroy them (do not just leave them lying in the field). Each gall you destroy means that dozens of little immature adelgids won't get a chance to emerge and attack your trees. Don't bother using an insecticide as the adelgids are well protected inside the gall tissue.
Wilted leaders of white pine and spruce trees that have been attacked by white pine weevil will begin showing up. These leaders can also be effectively pruned out when the first symptoms appear. Cut the terminal leader off an inch or two below the area damaged by the weevils. Use your fingernail and pull the bark away from the leader. Just below the bark, you will see the frass, small white larvae and maybe some chip cocoons where weevils are pupating. Cut out the infested terminal and burn it or otherwise destroy it (Do not leave the cut terminals lying in the field.). Then select a new lateral shoot on the upper 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.
Bird damage – broken terminal shoots
Each year we will find new growth on terminal shoots dead and hanging on the leader. At first glance, it looks like some insect may have girdled the shoot. However, these broken treetops are caused by birds perching on newly developed shoots. Breakage typically occurs this time of the year when the new tops are elongating, before they are stiff enough to support a bird perching. Taller trees seem to be more affected, as the birds look for higher vantage points.