Written by Fred Hoppe, Board Certified Master Arborist WI-0556B
With spring finally here it’s time to think about preventing insect and disease damage to your trees. The trees that first come to mind this time of year are pine and spruce. Species such as white spruce (Picea glauca), white spruce (Picea pungen) Austrian pine (Pinus nigra), and Scots pine (Pinus sylvestris) are very prone to disease and insect issues.
At Hoppe, we champion the right tree for the right spot. We like to recommend tree species that do not require a lot of long-term maintenance cost and effort. That said, a lot of people inherit mature pine and spruce trees on their properties and enjoy the benefits that they provide. When that’s the case, we have good strategies to deter the negative impacts from these disease and insect issues. In this article we’ll go over some of the major issues and treatments for spruce and pine trees.
WHITE SPRUCE & BLUE SPRUCE
Cytospora canker is one of the most common fungal diseases of white and blue spruce. Trees
that are 15 years old or more often show symptoms. Cytospora canker can kill trees, but more often simply makes trees so unsightly that owners opt to remove them.
Cytospora canker usually first appears on lower branches and progresses up the tree, although individual upper branches may show symptoms as well. Needles on infected branches turn purple, then brown. Diseased needles eventually fall off, and infected branches die. Infected branches often ooze a bluish-white sap.
Fungicide treatments are not effective in controlling this disease. To deter the spread of Cytospora canker immediately remove and destroy any diseased branches by pruning. Also minimize environmental stresses to any tree susceptible to Cytospora canker. Proper watering in dry conditions and fertilization, when needed, are very helpful in reducing tree stress.
Growth regulators, such as Cambistat, have been proven effective in helping slow the spread of this disease. Growth regulators help improve the health of root systems by increasing the density of absorptive roots.
Rhizosphaera Needle Cast
Rhizosphaera needle cast is another common disease of white and blue spruce in Wisconsin, making them unsightly and unusable in many landscape settings. The first noticeable symptom is purpling or browning and loss of the innermost needles on lower branches of spruce trees. Often, the youngest needles at the tips of branches remain healthy. Rows of small, black spheres form along the length of infected needles.
To deter the spread of needle cast consider treating affected trees with fungicides labeled for use on evergreens. Two to three applications timed weeks apart as new growth emerges is the best practice for deterring this disease. Along with fungicide treatments, proper watering and/or fertilization are important strategies for control of this disease.
AUSTRIAN PINE & SCOTS PINE
Diplodia Shoot Blight and Canker
Diplodia shoot blight and canker is one of the most common fungal diseases of Austrian pine and
Scots pine in Wisconsin. Initially, affected branch tips may ooze a large amount of resin. Eventually, these branch tips brown and die, with dead needles on these branches having varying lengths. As the disease progresses, sunken or swollen, discolored areas (called cankers) may form on infected twigs. The strategies to control diplodia shoot blight and canker are the same as for deterring needle cast on spruce trees.
Dothistroma needle blight is a common needle disease that can affect over thirty species of pine
trees. In Wisconsin, Austrian pines are most commonly and severely affected by this disease. The blight first appears as dark green, water-soaked spots on the needles. The spots become tan, yellow, or reddish-brown, and may encircle the needles to form bands. The tip of the needle beyond the band eventually dies, leaving the base of the needle alive and green. Fungicide applications and reducing environmental stress are key to deterring this disease. It is important to note that treatments will deter new infections, but not cure existing infections.
Zimmerman Pine Moth
Austrian and Scots pines are preferred hosts of Zimmerman pine moth. Zimmerman pine moth
larvae tunnel into new growth, causing shoot dieback, or into whorl areas, causing masses of pitch to form at the wound site. Repeated attacks by the larvae cause a weakening at the area of the infestation and make the branches and trunk susceptible to breakage.
To control Zimmerman pine moth, insecticide applications should be made in the spring to the trunk of infected trees before larvae migrate into tree trunks. As with all of the previously mentioned diseases, reducing environmental stress is a key part of the strategy.
Protect Your Beautiful Landscape
These are some of the most common issues we’re seeing right now, and we can help. If you have older spruce or pine trees, request a visit by one of our certified arborists. Our experts will inspect your trees and make the right diagnosis if there is an issue, so that proper action can be taken.
We also have a team of plant health care experts licensed in pesticide application and experienced in providing treatments for spruce and pine issues. We can recommend and perform root treatments to help trees cope with environmental stress, too. To schedule a visit to your yard, call us at 414.257.2111 or request a quote online.