This name is a synonym of Rhododendron temenium var. dealbatum (Cowan) D.F. Chamb..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 12304956) with original publication details: Notes Roy. Bot. Gard. Edinburgh 20(97): 83 1940.
This name was in version 1 of The Plant List, record tro-12304956, and has not been changed.