Diagnosis
Diagnose: Rhododendron Bud Blast
Use these observations to decide what to check next.
Tiny black bristles support true fungal bud blast
Look closely at several brown unopened flower buds.
A hard bud that stays attached and grows many tiny black pin-like bristles strongly supports bud blast caused by Seifertia azaleae.
A smooth brown or black bud after a freeze points to cold injury instead, especially when the exposed side of the shrub is worst. Soft water-soaked tissue or gray fuzzy growth after long wet weather fits Botrytis, while a narrow pointed bud may simply be a vegetative bud rather than a failed flower.