4-Phenylpyridazinone compounds (I) and their salts are new. 4-Phenylpyridazinone compounds of formula (I) and their salts are new. A : H, 3-6C-cycloalkyl or 1-6C-alkyl (substituted by n residues of halo, 3-6C-cycloalkyl, phenyl or halophenyl)； B1 : 3-6C-cycloalkyl or 1-6C-alkyl (substituted by m residues of halo, 3-6C-cycloalkyl, phenyl or halophenyl)； m, n : 0-3, with the proviso that m and n are not simultaneously 0； G : H, C(=O)R1, C(=L)MR2, SO 2R3, P(=L)R4R5, C(=L)NR6R7, E or R8； E : metal ion equivalent or ammonium ion； L, M : O or S； R1 : 1-6C-alkyl, 2-6C-alkenyl, 1-4C-alkoxy-1-6C-alkyl, di-1-4C-alkoxy-1-6C-alkyl or 1-4C-alkylthio-1-6C-alkyl (all substituted by n halo), 3-6C-cycloalkyl, phenyl, phenyl-1-4C-alkyl, heteroaryl, phenoxy-1-4C-alkyl or heteroaryloxy-1-4C-alkyl (all substituted by n residues of halo, 1-4C-alkyl or 1-4C-alkoxy) or completely saturated 3-6 membered ring comprising 3-5C and 1-3 heteroatoms of O, S or N, where the ring is substituted by n residues of halo, 1-4C-alkyl or 1-4C-alkoxy； R2 : 1-6C-alkyl, 2-6C-alkenyl, 1-4C-alkoxy-1-6C-alkyl or di-1-4C-alkoxy-1-6C-alkyl (all substituted by n halo), 3-6C-cycloalkyl, phenyl or benzyl (all substituted by n residues of halo, 1-4C-alkyl or 1-4C-alkoxy)； R3-R5 : 1-6C-alkyl, 1-4C-alkoxy, N-1-6C-alkylamino, N,N-di-1-6C-alkylamino, 1-4C-alkylthio, 2-4C-alkenyl or 3-6C-cycloalkylthio (all substituted by n halo), phenyl, benzyl, phenoxy or phenylthio (all substituted by n residues of halo, 1-4C-alkyl or 1-4C-alkoxy)； either R6, R7 : 1-6C-alkyl, 3-6C-cycloalkyl, 2-6C-alkenyl, 1-6C-alkoxy or 1-4C-alkoxy-1-6C-alkyl (all optionally substituted by n halo), phenyl or benzyl (both substituted by n residues of halo, 1-4C-alkyl or 1-4C-alkoxy) or H； or R6NR7 : 3-6 membered ring comprising 2-5C and 0 or 1 O or S； either X : H, 1-6C-alkyl or 3-6C-cycloalkyl； Y1 : halo, cyano, nitro, halo-1-6C-alkyl, halo-1-6C-alkoxy, 3-6C-cycloalkyl, 1-6C-alkoxy or phenyl (substituted by n halo atoms)； and Z : H, halo, cyano, nitro
