1. nematicidal agent containing at least one compound of formula (I) wherein B is 2-pyridyl, 3-pyridyl or 4-pyridyl, X is selected from the group consisting of halogen, nitro, cyano, hydroxy, amino, -SH , -SF, -CHO, -OCHO, -NHCHO, -COOH, -CONH, -CONH (OH), -OCONH, (hydroxyimino) -CC-alkyl, alkyl-CC, CC-haloalkyl having from 1 to 5 atoms halogen, CC-alkenyl, alkynyl-CC, CC-alkylamino, di (CC) alkylamino, alkoxy-CC, CC-haloalkoxy having 1 to 5 halogen atoms, alkenyloxy-CC, CC-galogenoalkeniloksi having from 1 to 5 halogen atoms, CC-alkynyloxy, CC-galogenoalkiniloksi having 1 to 5 halogen atoms, CC-cycloalkyl, CC-galogenotsikloalkil having 1 to 5 halogen atoms, CC-alkylcarbonyl, CC-galogenoalkilkarbonil having from 1 to 5 atoms halogen, -CONH (CC-alkyl), -CON (CC-alkyl), -CONH (OC-C-alkyl) ,, -CON (OC-C-alkyl) (CC-alkyl), CC-alkoxycarbonyl, CC- galogenoalkoksikarbonil having 1 to 5 halogen atoms, CC-alkylcarbonyloxy, CC-galogenoalkilkarboniloksi having 1 to 5 halogen atoms, CC-alkylcarbonylamino, CC-galogenoalkilkarbonilamino having 1 to 5 halogen atoms, -OCONH (CC-alkyl), -OCON (CC-alkyl), -OCONH (OC-C-alkyl), -OCO (OC-C-alkyl), -SCC-alkyl, -SCC-halogenoalkyl having 1 to 5 halogen atoms, -S (O ) -CC-alkyl, -S (O) -CC-halogenoalkyl having 1 to 5 halogen atoms, -S (O) -CC-alkyl, -S (O) -CC-halogenoalkyl having 1 to 5 atoms halogen, (CC-alkoxyimino) -CC-alkyl, (CC-alkeniloksiimino) -CC-alkyl, (CC-alkiniloksiimino) -CC-alkyl, (benzyloxyimino) -CC-alkyl, benzyloxy, -S-benzyl, benzylamino, phenoxy , -S-phenyl and phenylamino, n is 1, 2, 3 or 4 and when n is 2, 3, or 4, then the substituents X may be the same or different, Ri Ryavlyayutsya same or different and are selected from the group consisting of
