This name is a synonym of Phoradendron leucarpum subsp. macrophyllum (Engelm.) J.R. Abbott & R.L. Thompson.
The record derives from Tropicos
(data supplied on 2012-04-18)
which reports it as a synonym (record 19101022) with original publication details: Rep. U.S. Geogr. Surv., Wheeler 252 1878.
This name was in version 1 of The Plant List, record tro-19101022.