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Black Spot - (Diplocarpon rosae)
 HOSTS: Rose
DESCRIPTION: Round, black spots with slightly fringed margins on upper leaf surface. Yellow halos around the black spots can spread into yellow blothcs and leaves may fall prematurely. Raised, purplish spots may also be present on canes. LIFE
CYCLE: When weather is wet and humid and temperatures are 65-70 F, black spot is most infectious. It over winters on fallen leaves or infected canes. Black spot infects newly expanding leaves in the spring if leaves are continuously wet for 7 hours or more.
CULTURAL Keep water off of leaves and canes, or irrigate after 10 am and before 3 pm to maximize drying conditions. Prune to maintain good air movement. See Roses - Disease Resistant Cultivars. CHEMICAL Protect new leaves with sulfur if weather is wet and warm. |
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