The Resilience Hub & Portland Maine Permaculture Message Board › Black Knot of Plums

Black Knot of Plums

Jim S.
user 44116742
Limerick, ME
Post #: 7
Hi folks: does anyone have any advice for managing a black knot infection? Other than pruning it off and destroying the affected limbs, are there any fungicides, approved for organic use, that we should try?
Thank you in advance-
Mary L.
user 13657712
Portland, ME
Post #: 7
Definitely prune 2-4" below the knot and destroy the limbs. A regimen of fungicide is a preventative and might help control further spread. We use wettable sulfur before rainy periods if temp will stay below 80. Bonide makes a copper fungicide that works too.
Jim S.
user 44116742
Limerick, ME
Post #: 8
thank you mary! we will give that a try!
Jesse S.
user 29709632
Harrison, ME
Post #: 82
Good advise from Mary. My 2 cents: Cultivar selection can be a help, some plum varieties are more resistant/immune to black knot. Eliminating sources of spores is another preventative measure- native cherries are hosts for the fungus, so tracking these down and removing them should help as well. Easier to spot the knots after leaf fall. Improved air circulation through pruning and understory management is also a good idea, just pick a spell of dry weather to do that job, certainly not when the weather is like this! I burn the knots in my cob oven after I prune them out, then just remember to disinfect your pruning shears afterward so you don't inadvertently spread the disease.
David S.
stereoview
Washington, ME
Post #: 948
Apiosporina morbosa is ubiquitous on black cherry in Maine. Unless you live in a highly managed area, removing the cherry trees that pass them is not possible. It's a weed tree.
David Spahr
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