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Black Knot Management on Ornamental Plum: Pruning and Fungicides

Black knot (Apiosporina morbosa) forms black galls on plum/cherry limbs. Prune 2–3″ below galls in dormancy. Destroy prunings by burning before bud break. On large limbs, chisel out knot +1″ healthy bark, taper cuts.

Fungicides (captan, copper, thiophanate-methyl, lime-sulfur, sulfur) at bud break, every 7–10 days until mid-June. Remove wild Prunus nearby. Resistant cultivars for new plantings.

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