Home Yard and garden Solve a problem Plant diseases Black knot Quick factsBlack knot is a common fungal disease of Prunus trees including ornamental, edible, and native plum and cherry trees.Hard swollen black galls (tumor like growths) form on branches and occasionally on trunks.Many Prunus trees tolerate black knot. Tolerant trees have many galls throughout the tree with few negative effects on the health of the tree.Some Prunus trees are more severely affected by black knot. In these trees, leaves and shoots wilt and die on branches with galls.Management will vary depending on how severely the tree is affected by black knot. How to identify black knot Branch symptomsBlack knot galls are most noticeable during fall and winter after all the leaves have fallen.Knobby, swollen black growths called galls grow along the length of stems and branches.In early summer, young galls or new areas of growth on the edges of older galls are covered with velvety, olive-green spores.These galls turn...
