Accelerated biodegradation of the residual oxamyl (a systematic nematicide widely used for the control of soil pathogenic-nematodes), utilized at the recommended dose in soil cultured by banana plants and artificially infested with root-knot nematode (RKN, Meloidogyne incognita), was observed using algal bioassay studies. Algae such as Chlorella vulgaris, Scenedesmus obliquus, Anabaena oryza and Nostoc muscorum were used to determine the degradability enhancement of oxamyl by an accelerated biodegradation process. All oxamyl-degrading species were highly effective to enhance biodegradation of oxamyl compound. Moreover, algal species were effective for controlling RKN, M. incognita because of their enhanced defensive power gained from the oxamyl compound supplemented to the soil. Also, this was improved by the force of the integrated algal suspension to inhibit parasitic nematode. The incorporated application of alga, S. obliquus was the most successful one for oxamyl degradation in plants (75%) and soil (100%) by using HPLC analysis, and had an active promoting effect on banana health. Unlike, the alga, C. vulgaris was the most successful action in diminishing the nematode juveniles (J2s) count in soil (57.55%) and galls count on roots (52.87%).