Phytophthora Root Rot on Rhododendron causes roots to rot, leaves to wilt and yellow, and plants to decline quickly, often dying back from the base.

Botryosphaeria Dieback on Rhododendron causes leaves to droop and curl, while branches dry out and die back, leaving brown foliage on stems.

Ovulinia Petal Blight on Rhododendron causes soft brown spots on petals that spread fast, turning flowers limp, blighted, and unattractive.

Powdery Mildew on Rhododendron forms a white powdery coating on leaves, often causing curling, distortion, and a dull, unhealthy look.

Exobasidium Leaf and Flower Gall on Rhododendron causes thick, swollen, pale galls on leaves and flowers that later become white and deformed.

Ramorum Blight on Rhododendron causes dark leaf and shoot blight, with browning, blackened stems, and rapid dieback of affected growth.