is there any treatment for cytospora canker other than cutting off diseased limbs of my blue spruce tree
Cytospora canker is caused by a fungus, Leucostoma kunzei, that is most common in spruces like yours as well as pines, poplars and willows. Typically they appear on trees that are over 15 years old or under stress from weather conditions, shallow roots, injury or poor location. Sadly, cytospora may kill spruce trees over time after robbing them of their symmetry.
The disease is difficult to control, there are no chemicals registered for treatment and fungicide use is rarely effective. If you are certain that this is the problem afflicting your tree, your only remedy is to support the health of the tree to give it a chance to fight the fungus on its own and employ Integrated Pest Management techniques. Specifically,
- Support your trees' health and resilience by watering when dry, improving the soil structure and feeding to increase vigor.
- Do not cut into the bark unnecessarily as wounds are the pathogens primary point of entry.
- If the canker is present on branches, carefully remove them from several inches below the infection. Prune flush with the branch collar.
- Do not prune in wet conditions which will risk spreading the fungal infection. Late winter is the safest time. Sterilize your tools after pruning. Burn or transfer all infected material from the site.
- The tree may heal itself by forming a callus around the canker. Do not cut into cankers or the encapsulating calluses or you may renew fungal activity.
If you are forced to remove the tree or trees, consider replacement with trees other than blue and Norway spruces which are most frequently afflicted with cytospora. Make sure to space trees generously to improve air circulation and reduce the risks of infection.
Courtesy of NYBG Plant Information Service