This name is a synonym of Parthenium tomentosum var. stramonium (Greene) Rollins.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 9E8E1A1A-83C5-4FDA-9FA5-1F03A6081B42) with original publication details: 240 1901.
Full publication details for this name can be found in IPNI: http://ipni.org/urn:lsid:ipni.org:names:184072-2.
This name was in version 1 of The Plant List, record gcc-16787, and has not been changed.