Nematostatic Activity of Oxamyl and N,N-Dimethyl-1-cyanoformamide (DMCF) on Meloidogyne incognita Juveniles

Abstract

The nematostatic activity of oxamyl, methyl-N',N'-dimethy]-N-hydroxy-l-thiooxamimidate (oxamyl-oxime) and N,N-dimethyl-l-cyanoformamide (DMCF) was studied by immersing 10 Meloidogyne incognita second-stage juveniles into aqueous solutions of various concentrations of each chemical. At concentrations of 500 to 8,000 [mu]g/ml, oxamyl quickly immobilized immersed juveniles. In all other concentrations studied (down to 4 [mu]g/ml), oxamyl stopped or reduced movement of juveniles within 24 hours. DMCF also quickly immobilized juveniles at concentrations of 4,000 and 8,000 [mu]g/ml and reduced movement at 2,000 [mu]g/ml. Lower concentrations had no observed effect on movement. In solutions of the oxime from 2,000 to 8,000 [mu]g/ml, some reduction of movement was observed, but most juveniles maintained some motion over a period of 24 hours. Juveniles were transferred to water from 4,000 [mu]g/ml solutions of oxamyl and DMCF after various intervals of time in order to determine the effect of duration of exposure to the chemicals on the ability of the immobilized juveniles to recover normal motion. Some recovery was observed even after 24 hours of exposure to DMCF, but none after exposure to oxamyl for longer than 40 minutes. Key words: biological activity, Meloidogyne incognita (Southern root-knot nematode), metabolites, mode of action, nematostatic, N,N-dimethyl-1-cyanoformamide (DMCF), oxamyl (Vydate), oxamyl-oxime.