This name is a synonym of Ageratum conyzoides (L.) L..
The record derives from TICA
(data supplied on 2012-02-11)
which reports it as a synonym (record 2A287B44-C6B1-47C6-BA83-99DA2333C818) with original publication details: n. Flum. 339. 1825. 339 1825.
This name record (from TICA) was not included in version 1 of The Plant List. It is possible the same name was included from a different data source, to check this you can search for Cacalia mentrasto in version 1 of The Plant List.