Occasionally, Phomopsis sp. will cause twig dieback very similar to BotrYosphaeria. Infected twigs first show wilting and death of leaves on one or more branches. This discoloration may extend from several inches to several feet along the stem. Twig blight can be controlled on cultivars that are not severely stressed nor highly susceptible by promptly pruning out and disposing of the diseased branches. Carefully, check to be sure all the discolored stem tissue has been correct pruning practices are not followed.
Fungicides are of little value.
Phytophthora Dieback Dieback of hybrid rhododendron is a foliar disease caused by several species of the fungus Phytophthora . 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.