Plant Pathology: Extension: Plant Disease Library

Petal blight - Ovulinia azaleae

Azalea/Rhododendron

Disease Symptoms:
Mostly a problem on azalea. Tiny, round pale spots that rapidly enlarge to irregular blotches are produced on infected flowers. Flowers quickly (1-day after infection) turn brown, limp, and mushy. Under humid conditions, affected flowers are covered in a white mold growth. Affected blooms hang on plants for weeks, even months. Hard, black survival and fruiting bodies (sclerotia) are produced on the affected blooms. Blossoms eventually drop from the plant.

Disease Management:
Rake and remove flower debris from underneath bushes. Remove old flowers from plants. Mulch around base of plants. Fungicides can be applied to base of plants to prevent sporulation from sclerotia, but this marginally effective. On large azalea plantings, make fungicide applications beginning just before blooming and continue at 1-week or less intervals during entire bloom period.

Click here for more information on Sclerotinia

Compiled by: Dr. Jean L. Williams-Woodward, UGA Extension Plant Pathology, Athens