 |
Symptoms: Yellowing and browning of the inner needles (second year an older) on branches near the base of the tree. Photo by Chad Behrendt |
Rhizosphaera needle cast is a fungal disease that causes needle loss on the inner portion of the lower branches. Rhizosphaera needle cast is probably the most common disease affecting spruce. |
Symptoms: Yellowing and browning of the inner needles (second year an older) on branches near the base of the tree. Photo by Chad Behrendt |
 |
Symptoms: Brown, infected needles drop from the tree, leaving green growth at the branch tips. Photo by Chad Behrendt |
 |
Symptoms: Black fruiting bodies of the fungus (pycnidia) emerge from the stomata, which appear as rows of white dots. Photo by Department of Plant Pathology |
 |
Symptoms: Branches with severe needle loss near the base of the tree eventually die, as the disease progresses upward. Photo by Plant Disease Clinic |
| Causal organism: | Rhizosphaera kalkhoffii |
| Over wintering: | In plant material (needles) |
| Months of infection: | Most commonly May-June (possibly the entire growing season) |
| Method of dispersal: | Rain and wind |
| Infection point: | Needles |
| Control: | Reduce stress and maintain plant health by properly watering, fertilizing, and mulching trees. Prune dead or dying branches during dry weather. Plant resistant/native species on the appropriate site. |
| Labelled fungicides (First Application) |
Chlorothalonil (Daconil 2787) (late May-June) |
| Comments: | Colorado blue spruce is highly susceptible in Minnesota. White and Norway spruce are more resistant. Stressed trees are more susceptible than healthy trees. Aged or stressed inner needles may also be infected. |
| For additional info | Back to Spruce Diseases |