Symptoms Figure 1. Black spots with feathery margins characteristic of black spot. The dark color and feathery appearance easily distinguishes black spot from other leaf diseases of roses. Spots may vary in size. They sometimes coalesce, but more often remain as distinct spots.
Lower leaves are usually the first to become infected followed by middle and upper leaves.
Excessive leaf drop reduces stem length and size, as well as number and quality of leaves and blossoms. It also weakens plants and increases the risk of injury from cold winter temperatures. In resistant cultivars, or during dry weather, only small spots may form without yellowing and defoliation. Lesions on canes rarely kill branches, but are very important to the pathogen's survival over the winter. Infection of petioles, stipules, peduncles, fruit and sepals may result in inconspicuous, reddish-purple spots.