VARIOUS WOODY ORNAMENTAL PROBLEMS
VARIOUS WOODY ORNAMENTAL PROBLEMS
Two diseases which commonly affect woody ornamentals in the Michigan area are cytospora canker of blue spruce and tip blight of junipers. Both of these are fungal diseases, and can be detected by the black spread of the fungus.
Cytospora Canker of blue spruce is one of the most common diseases of Colorado blue spruce in Michigan, although it also attacks other spruces and Douglas fir. The fungus infects trees that are older than 15 years, as well as trees that are stressed by drought, winter injury, etc. The disease generally progresses slowly up the tree; one or several branches become infected and die yearly. The disease is detectable by the white patches of pitch or resin which exude from sites where the fungus has caused a canker and by the minute, black fruiting structures of the fungus which are found beneath the surface of the bark.
Cytospora Canker is best controlled through the improvement of tree vigor by the implementation of fertilization and weed control at proper times. Infected branches should be removed and destroyed to prevent the spread of the disease.
The fungus Phomopsis juniperovora causes tip blight of junipers. This disease commonly causes losses among nursery seedlings, but can also occur on older plants. When affected by this disease, the tips of infected branches turn brown and then die back progressively until a branch or an entire seedling is killed. Small, black fruiting structures of the fungus can be seen on affected plant parts in advanced stages of the disease.
Tip blight may effectively be controlled by Benomyl, and can be prevented by cultural practices, such as the provision of good drainage and the avoidance of overhead sprinkling.
SOURCE: D. Roberts, Botany and Plant Pathology Michigan State University Hortopics: 11/84.
