Answer: Two possibilities come to mind. Rhododendron bud blast, in which buds fail to open, turn brown and dry. They might stay on the plant for a few years. The bud itself is covered in tiny, black, bristly fungal growths. It is spread by rhododendron leafhoppers as they lay their eggs in the buds. If the fungus is present, there is little that can be done to control the leafhoppers, which show up in mid to late summer. Pick off and destroy any damaged buds before this so they don't spread it around further. These fungal growths are what make it different from dry bud, which has similar symptoms. Dry bud is caused by a period of dry weather while the buds are forming at the end of summer. Even a few days of drought can create a problem, so make sure plants are well-watered and apply a thick layer of mulch to retain moisture. Finally, all those moves can be stressful and may have contributed to the problem.
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