Black Spot
(fungus - Marsonnina rosea - teleomorph Diplocarpon rosae): Black
spots ranging in size from one-eighth to one-half inch or greater in diameter
form on leaves. Spots can occur on either leaf surface as well as petioles, twigs
and canes. Infected leaves soon turn yellow and drop from the plant. This results
in plants becoming weakened to the point where few blossoms are produced and plant
life is endangered. Consistent use of protectant fungicides is necessary for black
spot prevention in most areas. The fungus persists in fallen leaves and canes.
Destroy all fallen leaves and prune infected canes severely during late winter.
