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Several different types of fungi produce blights in azaleas and rhododendrons: Ovulinia spp., Briosia spp., Pestalotia spp., Monilinea spp., and others. The flowers, buds and growing shoots of infected shrubs become spotted, blotched and discolored. In addition, they may be covered with powdery fungal spores or a thin mat of fungal strands. Azalea petal blight (Ovulinia azalea), also known as azalea flower spot and Ovulinia flower blight, is a common disease of azaleas in the southeastern states. It first appears as small pale spots on the inner surfaces of the petals of colored flowers and as brown spots on white flowers. These spots rapidly enlarge until the whoile flower collapses. Small dark resting bodies of the fungus overwinter on dead flowers and in the soil.
Prune and destroy infected branch tips, leaves, and flowers. The fungi that cause blight overwinter on the ground in dead flowers and other debris, so gather and destroy diseased plant material promptly. To prevent the disease from spreading, avoid overhead watering while the plants are in flower. Plant azaleas or rhododendrons where they will be protected from sunscald and winter injury, which makes shrubs more susceptible to blight.
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