This name is a synonym of Achillea ageratifolia subsp. serbica (Nyman) Heimerl.
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 28EE3F63-EE08-4F88-983E-8C63C7E7706F) with original publication details: 102 .
This name was in version 1 of The Plant List, record gcc-94176, and has not been changed.