Black Fungus on Pussy Willow

(Question)

Hello: I had a pussy willow tree that developed a black fungus on the bark. It looked like black paint had been spilled on the truck and branches. I took the tree down but now there is lots of new growth from the stump. Would this type of fungus be a root fungus or a surface fungus? Should I allow the growth to continue or take it down again and out of the garden?

 

(Answer)

Thanks for getting in touch with Toronto Master Gardeners. Most likely your pussy willow (Salix discolor) was infected with black canker cause by a fungus, Glomerella miyabeana as well as willow scab caused by Venturia saliciperda.  These fungal diseases are often present at the same time and are referred to as willow blight. However, what you describe definitely sounds like black canker. These fungi overwinter on dead twigs and will spread in the spring, especially in wet weather conditions, to other parts of the plant.

By removing the infected tree, you may have cleared the problem. Even so, there may be some fungal spores lingering around the stump which may infect the new growth. [These are not root fungi]. Check the new growth for signs of the disease–are the leaves healthy? If they shrivel and die after emerging, then the disease is still present; carefully remove the new growth during dry weather to prevent further spread of the disease.  However, if the twigs and leaves seem to be healthy, then you might decide to let them grow.

For further detailed information about Black canker on willows, please see: http://plantclinic.cornell.edu/factsheets/willowblackcanker.pdf and http://www.agr.gc.ca/eng/science-and-innovation/agricultural-practices/agroforestry/diseases-and-pests/scab-and-black-canker-of-willow/?id=1367429536020

Good luck with your willow.