By: Dominick Bierdek, Certified Arborist WI-0635A
What is causing all the tiny little pencil lead size holes in the bark of my evergreens? I have a nice wind block of Pines and Spruce. Some of the more crowded trees died quickly and they all have these holes like someone shot it with a shotgun.
If you see a bunch of pencil lead size holes in the bark of your evergreen, it would be easy to think that someone took aim at your tree with a shotgun. However, these holes are likely the work of the Ips spp. beetles, commonly called engraver or bark beetles. This insect problem has increased in recent years due to the past drought conditions that made the trees more susceptible.
Ips beetles attack by colonizing a tree. The young feed in the cambium destroying it and interfering with the sap flow, killing the tree. They can spread quickly if left unchecked. Ips beetles attack all species of pine, spruce and sometimes Arborvitae. Keeping a tree healthy and vigorous is the best preventive medicine.
Healthy, vigorous trees often have a degree of natural resistance to attacks. Start with proper planting and placement of evergreens. Recently planted trees, especially in unfavorable sites (e.g., heavy wet or compacted soils and shade), are more subject to attack. Overcrowding of trees can lead to stress. Removal of crowded, weaker trees is important.
Maintain a two- to 3-inch mulch layer underneath the drip line to avoid stress. Leave a gap of a few inches around the trunk. This also helps avoid injury from mowers or weed whips, conserve soil moisture, and lessen competition from grasses. Water trees when dry. Avoid grade changes and flooding.
Dead or dying wood, which might attract beetles, should be pruned out. Severely infested trees or “brood” trees should be removed as they only produce more pests. There are two to three generations per year, so large numbers can build up quickly and can even attack adjacent healthy trees. Up to three trunk sprays may be needed to kill adults tunneling through the treated bark layer. Sprays will not kill ones that have already penetrated the sapwood. Complete coverage and correct timing are necessary for effective control.
When trying to decide what steps to take with an evergreen infested with Ips beetles, your Wachtel Certified Arborist can assess the tree, evaluate the extent of damage in the landscape, and determine the need for cultural or chemical controls.
© Copyright 2008 – Wachtel Tree Science & Service, Inc.