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Your tree had a fungus calledYour tree had a fungus called Black Knot.  You need to prune out any infected areas, preferably before bud break. Prune 2 to 4 inches below each knot. If pruning is not possible because knots are present on major scaffold limbs or the trunk, they can be removed by cutting away the diseased tissue down to healthy wood and out at least 1/2 inch beyond the edge of the knot. Burn or bury the prunings in early spring. Fungicides are necessary and will provide the greatest benefit if applied before rainy periods, particularly when temperatures are greater than 55 degrees F. You need to maintain pruning, too.

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