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| Black knot fungus is a common cause of disease in least 25 Prunus species, mainly cherries and plums. |
Black knot fungus is a common cause of disease in least 25 Prunus species, mainly cherries and plums. It is very common on native pin and chokecherries in Ontario.
Often referred to as “cat poop on a stick” because of its shape and colour (see photo), this fungus can cause lots of damage to cherry and plum trees, says Sylvia Greifenhagen, OFRI's pathology research forester.
She recommends that people who are planning to plant cherry or plum trees ask their local greenhouse or garden centre about varieties that are resistant to black knot fungus.
"If your trees are showing signs of the disease, the best long-term strategy is to plant resistant varieties—even if you are still getting good fruit production on your original trees—so that they have time to mature before your existing trees become severely infected," she advises.
"Recommended control strategies include pruning out infected material and burning or removing it from the site, and in fruit orchards, using fungicide sprays."
Want to read more?
Black Knot of Plums factsheet (OMAFRA)
Black Knot (Toronto Parks, Forestry, and Recreation)
