Remove and destroy diseased leaves and plants. Fungicides containing either ferbam, mancozeb, propiconazole or lime sulfur are recommended for homeowner use. Apply all chemicals according to directions on the label. The fungus is most active when temperatures are 62 to 72 F and conditions are moist. Diseased flower petals have small, light-colored spots surrounded by reddish halos, which can quickly expand into large, irregular blotches.
Buds fail to open and often droop.
Thrips can cause similar damage to half-open buds, so inspect plants carefully. Keeping the area clean is more important than anything else. Collect and discard all fading flower blossoms and leaves. Provide good air circulation, and avoid wetting the leaves when watering. Disease easily develops on canes that have been damaged and canes that are kept too wet by a manure mulch or wet leaves.