This name is a synonym of Rhododendron thomsonii subsp. lopsangianum (Cowan) D.F. Chamb..
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 50060621) with original publication details: Acta Bot. Yunnan. 6(2): 160 1984.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:923791-1.
This name was in version 1 of The Plant List, record tro-50060621, and has not been changed.