Black Knot disease on Bird Cherry tree - Ask Extension
We have a bird cherry tree, planted around 1980, which has been otherwise healthy until this spring. It is approximately 30 feet tall. At that time I...
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Black Knot disease on Bird Cherry tree #846001
Asked August 16, 2023, 5:47 PM EDT
We have a bird cherry tree, planted around 1980, which has been otherwise healthy until this spring. It is approximately 30 feet tall. At that time I noticed growths which have been identified by our arborist as black knot. The tree is one of the few Bird cherries in NE Ohio and the recipient of the local community's Heritage Tree award in 2018. From what we can see through the foliage, the lower branches are affected - though not all. We have had it sprayed with fungicide and plan on pruning it during the dormant season.
The tree is located in a flowering tree grove of 41 trees including a few other ornamental cherries (though not immediately adjacent), magnolias, crab apples, serviceberries, buckeyes and dogwoods.
If at all possible, we would like to salvage the tree, but understand that it may not be possible. Any suggestions you may have would be greatly appreciated.
Cuyahoga County Ohio
Expert Response
Hello,
It sounds like you are following the correct protocols for managing black knot fungus on your cherry tree. Black knot fungus only infects Prunus species (plum, peach, cherry, etc) so other than the cherry trees, the rest of the trees in your grove would not be susceptible. You should closely monitor all of the cherry trees and keep in mind that the characteristic knots from this fungus typically develop the year after initial infection.
When pruning, be sure to prune 2-4” beyond the infected area to remove all of the fungus. Pruned branches should be burned, buried, or otherwise removed from the area to prevent further spread.
Pruning and removal of infected material is a vital step to controlling black knot. Without it, fungicide application will not be as effective.
Depending on the severity of the infection, multiple fungicide treatments will most likely be needed. If there are other infected trees in your area or unmonitored stands of wild cherry or plum nearby, treatments may be needed from bud break until early summer. If this seems to be an isolated infection, fungicide treatment from white bud stage to shuck split should be adequate. Timing of treatments is also important. They will be most effective if applied before rainy periods when the temperature is at least 55°F. A reputable arborist specializing in fruit trees should be able to offer good guidance.
These two publications from Ohio State University provide more detailed information about black knot fungus; its life cycle, treatment, and cultural control methods. The second is referenced in the first as providing the most current fungicide recommendations.
https://ohioline.osu.edu/factsheet/plpath-fru-31
https://cuyahoga.osu.edu/sites/cuyahoga/files/imce/Program_Pages/ANR/DigIn/Controlling%20Diseases%20and%20Insects%20in%20Home%20Fruit%20Plantings%2C%20Bulletin%20780%20%28whole%29.pdf
It sounds like you are following the correct protocols for managing black knot fungus on your cherry tree. Black knot fungus only infects Prunus species (plum, peach, cherry, etc) so other than the cherry trees, the rest of the trees in your grove would not be susceptible. You should closely monitor all of the cherry trees and keep in mind that the characteristic knots from this fungus typically develop the year after initial infection.
When pruning, be sure to prune 2-4” beyond the infected area to remove all of the fungus. Pruned branches should be burned, buried, or otherwise removed from the area to prevent further spread.
Pruning and removal of infected material is a vital step to controlling black knot. Without it, fungicide application will not be as effective.
Depending on the severity of the infection, multiple fungicide treatments will most likely be needed. If there are other infected trees in your area or unmonitored stands of wild cherry or plum nearby, treatments may be needed from bud break until early summer. If this seems to be an isolated infection, fungicide treatment from white bud stage to shuck split should be adequate. Timing of treatments is also important. They will be most effective if applied before rainy periods when the temperature is at least 55°F. A reputable arborist specializing in fruit trees should be able to offer good guidance.
These two publications from Ohio State University provide more detailed information about black knot fungus; its life cycle, treatment, and cultural control methods. The second is referenced in the first as providing the most current fungicide recommendations.
https://ohioline.osu.edu/factsheet/plpath-fru-31
https://cuyahoga.osu.edu/sites/cuyahoga/files/imce/Program_Pages/ANR/DigIn/Controlling%20Diseases%20and%20Insects%20in%20Home%20Fruit%20Plantings%2C%20Bulletin%20780%20%28whole%29.pdf
Thank you for your informative response. We are doing our best to save this historical cherry and will heed your advice.
Best,
Pat Agatisa
Sent from my iPhone
Sent from my iPhone
On Aug 18, 2023, at 3:18 PM, Ask Extension <<personal data hidden>> wrote:
You’re welcome and good luck
