I have a Pagoda Dogwood planted three years ago that after the first winter has been experiencing die-off of successive branches. I have lost half the bulk of the tree with two of three remaining branches dead, dying or (so far) ok. Attached photo shows what may be a symptom – discoloured bark. The leaves begin to turn yellow on a branch and by the end of the season the branch is dead. In this photo the central stem is dead and the right stem is dying. You will see a central stem that I had to remove last year.
I suspect that it is too late to save the tree but would appreciate knowing what has infected it, and what this might mean for replacing the tree. Could I replace with another dogwood, or should I try something else, or will any other tree also have problems with residual disease in the soil? Thank you for your time and expertise!
Thank you for contacting the Toronto Master Gardeners with your query.
Pagoda dogwoods (Cornus alternifolia) are a beautiful addition to a shady area in a garden. It is generally quite disease-resistant as long as it is not under stress. Pagoda dogwood does not tolerate drought. Regular watering and the addition of mulch (away from the trunk) will keep the roots hydrated and cool during hot summer spells.
It is difficult to identify from the photo what specific disease is affecting your Dogwood. I suspect two possible fungal pathogens may be the cause of the damage: Golden canker fungus (Cryptodiaporthe corni) or Dogwood anthracnose (Discula destructiva). Pagoda dogwoods are more susceptible to the Golden canker than anthracnose.
The websites below have excellent descriptions and photographs of the symptoms of each of these diseases. These may help in identifying your problem. You may wish to consult an arborist to be absolutely sure.
If it is Golden canker, you should remove the diseased branches 6-8 inches below the fungus, disinfecting your pruning tools between cuts. This fungus generally does not kill the trunk.
If you decide to remove your tree altogether, I would recommend selecting a tree that is resistant to whichever fungus your Pagoda dogwood has.
https://extension.umn.edu/plant-diseases/golden-canker-pagoda-dogwood
https://hort.extension.wisc.edu/articles/golden-canker-cryptodiaporthe-canker/
https://plants.ces.ncsu.edu/plants/cornus-alternifolia/
https://ag.umass.edu/landscape/fact-sheets/dogwood-anthracnose