In North Carolina, P. cactorum , and P. citricola have been isolated from diseased plants. Rhododendron dieback is primarily a problem on container-grown hybrid rhododendrons in nurseries. Symptoms Lesions first appear as chocolate-brown spots on young, expanding foliage and stem. The fungus grows from initial lesions down the stem into older leaves. Lesions on mature leaves are characteristically wedge-shaped, extending from the petiole toward the leaf margin.
Infection spreads rapidly in warm days.
The fungus progresses slowly in older woody stems, but can kill any size plant. Diagnosing Rhododendron dieback caused by Botryosphaeria and Phytophthora . Botryosphaeria Phytophthora 1. Mostly in landscapes. Mostly in container nurseries.