Most of our rhododendrons are suffering from bud blast, identifiable by the black hairs that appear on the flower buds, which will no longer bloom. The buds don’t rot and fall off, they stay on the bush for a couple of years, so attention is required to get rid of the problem.
The black hairs are caused by a fungus, which infects the plant when leafhoppers lay their eggs. The only environmentally friendly way to get rid of it is by painstakingly removing all of the infected flower buds and either incinerating them or throwing them in the rubbish – do not compost or leave them on the ground. RB and I have a job ahead of us to get the rhodos back to blooming beauty.