A method of treating a grass-carrying surface, the method comprising applying to the g carrying surface: (a) a compound of formula (I): or a derivative salt thereof wherein L is a linking group； each of R1, R2 and R3 is independently selected from an optionally substituted alkyl, alkenyl, aryl or alkoxy group； R4 is oxygen or an optionally substituted alkyl, alkenyl or aryl group； each of R5 and R6 is an optionally substituted alkyl, alkenyl or aryl group； and n is 0 or 1； (b) at least one cationic biocide； (c) a hydrocarbyl saccharide compound； and (d) a nonionic surfactant.
