This name is a synonym of Rhododendron decorum subsp. diaprepes (Balf. f. & W.W. Sm.) T.L. Ming.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12304788) with original publication details: Notes Roy. Bot. Gard. Edinburgh 10(47–48): 139–141 1917.
This name was in version 1 of The Plant List, record tro-12304788, and has not been changed.