Which plant part is most commonly affected by black knot?

Black knot, a fungal disease caused by the pathogen Apiosporina morbosa, primarily targets the stems of certain plants, particularly those in the Prunus genus, which includes cherries and plums. The disease manifests as dark, swollen galls or 'knots' that form on the stems and branches. These galls disrupt the flow of nutrients and water, which can weaken the plant and hinder its growth.

Focusing on the stems is crucial because that’s where the infection primarily occurs, leading to significant structural damage and decline in the health of the affected plants. Although other plant parts like roots, leaves, and flowers can be affected by various diseases and pests, black knot specifically emphasizes the stems, making the identification and management of this disease particularly important for maintaining the health of susceptible ornamental and fruiting trees.