Four typical systemic herbicides,one contact herbicide and auxiliaries with the best performance on the control of Solidago canadensis in July 2017 were used to screen the best herbicide and optimal dosage for controlling S.canadensis in Guogongdu,Changsha county from April 19to21in2018.Results indicated that 7 groups of agents,including glyphosate-isopropylammonium41% AS 1 756.50 g/hm~2,hexazinone 25%SL1 718.50 g/hm~2, glyphosate-isopropylammonium41% AS 769.20 g/hm~2+agricultural organosilicon synergist 600.00g/hm~2, hexazinone 25% SL 1 407.25 g/hm~2+agricultural organosilicon synergist 600.0...