The efficacy of aqueous leaf extracts of Hyptis suaveolens (L.) Poit and Ocimum basilicum (L.) in the control of Meloidogyne spp infecting Onion, Allium cepa (L.)
The efficacy of aqueous leaf extracts of Hyptis suaveolens and Ocimum basilicum in the control of Meloidogyne spp infecting Allium cepa L (Onion) was investigated using sterile soil that was filled into polythene planting bags. Two varieties of onion (Safari and Belami) and three concentrations (60 mg/ml, 45 mg/ml and 30 mg/ml) each of H. suaveolens and O. basilicum leaf extracts were used. Furadan at 7.7 mg/ml was used as a positive control and the negative control was untreated. Each treatment was replicated three times in a completely randomized design (CRD). Onion raised in steam-sterilized soil were infected with 2000 juveniles of root-knot nematodes four weeks after planting. Two weeks thereafter, the different concentrations of the leaf extracts of the test plants and furadan were applied. The plants were then monitored for growth and yield parameters at harvest. Phytochemical analysis of the aqueous leaves extracts of the two plants were carried out. The result showed that growth and yield data of infected but treated onions were higher than their infected but untreated counterparts. Onions treated with O. basilicum at 60 mg/ml had the highest performance: plant height (39.90 cm), dry bulb weight (16.70 g) among others followed by those treated with H. suaveolens at 60 mg/ml, plant height (36.30 cm), dry bulb weight (13.20 g) then furadan, plant height (36.17 cm), dry bulb weight (14.93 g) while the untreated onions had the least growth and yield data, plant height (24.40 cm), dry bulb weight (8.40 g). Statistical analysis revealed that the various treatments significantly increased plant height, collar girth and leave number (p< 0.05) as compared to the untreated control. Variety Safari generally performed better than variety Belami. Statistical analysis also showed significant difference (p< 0.05) for all parameters. Phytochemical analysis showed presence of some bioactive compounds such as saponins, alkaloid, tannins among others. The study revealed nematicidal efficacy of the aqueous leaves extracts of the test plants, therefore, they can be viable alternatives to synthetic nematicides in nematode management.
OB Okechalu, ND Zwalnan, OA Agaba, LS Danahap