Synthetic chemicals have been used to control plant pathogenic nematodes in the farmers fields. These chemicals, though valued for their effectiveness, are costly and may constitute health hazards to farm households and the environment. Reducing these situations in the farms through use of natural plant extracts is one of the challenges in Nigeria. Powdery extracts of Jatropha curcas, Parkia biglobosas, Newbouldia laevis, Ficus exasperata and Cassia alata were evaluated for the control of M. incognita in yam bean (Sphenostylis stenocarpa Hochst ex A. Rich) at the University of Nigeria, Nsukka in Nigeria. Newbouldia laevis extract significantly (P<0.05) controlled the galling of Meloidogyne incognita, while the efficacy of other extracts were insignificant (P >0.05). Newbouldia laevis extract had significant effects on the height of the plant. Significant difference was observed on the plants height. Newbouldia laevis extract reduced the number of galls from 1.89 to 1.18 and increased the height from 106.1 to 213.3 cm and the number of leaves from 59.2 to 69.2 compared with control (water treatment). Cassia alata extract had a significant effect on both leaf numbers and stem height of the plant. It increased the number of the leaves from 59.2 to 81.3 and the height from 196.1 to 201.3 cm, and the number of root gall from 1.89 to 2.49.

The antifungal effect of ethanol leaf extracts of five plants, (viz. Jatrohpa curcas L, Newbouldia laevis (P. Beauv.) seem. Ex Bureau, Ficus exasperate Vahl, Parkia biglobosa (Jacq.) and Cassia alata L.) Seed plus 30 wettable solvent (WS) and Water on some Seed borne fungi: Aspergillus niger and Fusarium oxysporium of African yam bean (Sphenostylis stenocarpa) seeds was studied in vitro using agar plate method of isolation. The efficacy of the treatments was tested separately on the individual fungal isolates. All the plant extracts except Newbouldia laevis (P. Beauv.) seem. Ex Bureau, significantly (P > 0.05) inhibited the radial hyphal growth of Aspergillus niger. Jatropha curcas L extract gave the highest inhibition at all levels of concentrations while Parkia biglobosa (Jacq.) was the least. The positive control; Seed plus 30 wettable solvent (WS) inhibited the growth of A. niger significantly (P > 0.05) while water had no inhibition on the growth of the fungus. On the other hand, Jatropha curcas L., Cassia alata L. and Parkia biglobosa (Jacq.) extracts had inhibitory effects on the hyphal growth of Fusarium oxysporium while Newboudia laevis (P. Beauv.) seem. Ex Bureau and Ficus exasperate Vahl. extracts showed no inhibition on the growth of the fungus at all levels of concentrations. Parkia biglobosa (Jacq.) extract was the most effective whileCassia alata L. extract was the least in the inhibitory efficacy. The positive and negative controls; Seed plus 30WS and Water respectively recorded no significant inhibition on the hyphal growth of Fusarium oxysporium. The ethanolic leaf extracts of Jatopha curcas L., Parkia biglobosa (Jacq.), and Cassia alata L. which are very cheap and environmentally safe were proved promising for protecting African yam bean seeds against Aspergillus niger and Fusarium oxysporium.