One of the most common tree questions we get is, “Why don’t you sell blue spruce at your tree sales?”
It is no coincidence. Most conservation districts avoid blue spruce on purpose! In Michigan, there are many factors that compete against the tree and have caused survival rate to drop.
Colorado Blue Spruce (Picea pungens) were widely popular in the 1980s and 1990s, being one of the more popular landscape and backyard trees planted. Due to that “overuse”, many diseases and pests associated with blue spruce have also flourished.
The tree is not native to Michigan or much of the east coast. Colorado Blue Spruce is, to no surprise, native to Colorado and much of the west mountainous region of the U.S. It likes dry weather and sandy soil. Much of lower MI has heavier soils and lay. These poorly drained soils hold in water, keeping tree roots wet. In general, blue spruce do better in nutrient-poor and well-drained soil. Poorly drained soils stress the trees and welcome pests and disease.
Many of the blue spruce around my house are in sandy soil, they are still dying. The trees are dropping needles fast- this is due to one of several needle-cast diseases. The disease lives on the current year’s shoots and, the following year, the needles will shed leaving the branch bare.
Canker disease can be identified by the presence of excessive sap over the trunk and base of the tree. This is caused by a fungi (who thrive in wet weather). Three common ones are Phomopsis, Cytospora, and Diplodia.
It is easy for insects to colonize and thrive on an already stressed tree. Gall adelgids suck plant sap on the young plant shoots and create gulls that will deform the tree. Spruce spider mites cause the needles to discolor and fall off. Sometimes this can be confused with needle-cast.
If you have blue spruce in your yard, it is almost certain they will eventually feel the effect of one of these pests and ultimately die prematurely. Trimming the dead and diseased branches can help slow the spread of infestation. I usually burn the branches in my fire pit so whatever pest is on them will not continue to live as they would if I threw them in a brush pile. Unfortunately, there are no real silver bullet to fixing failing blue spruce trees. Arborists or landscapers can spray them, but it is costly and depending on the site and soil conditions, treatment may not help.
More information on your poor blue spruce trees can be found in a great MSU Extension article: What is Spruce Decline & What Should You Do About It – MSU Extension
By: Katie Hafner, Soil Conservationist