My 20-foot Canadian Cherry Tree with a 9-inch diameter has had black knot for several years. Despite trimming infected branches for two years, it persists. What are my options now?
Continue to prune out infected areas. Fungicide treatments applied in the early spring have had little effect on control. Prune now where you see the early stages and ones you have missed a little latter. It is a tough disease to control, though.
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