Management of Root-knot Disease in Okra with Poultry Manure and Leaf Extracts of Senna alata

This research was conducted with the aim of evaluating the nematicidal effect of aqueous leaf extracts of Senna alata, and poultry manure against Meloidogyne incognita on okra (cv. Clemson spineless). The concentration of S. alata leaf extract (0.20, 0.40, 0.60, 0.80 g/ml) and a control (0.00 g/ml) were combined with poultry manure (0.00 t/ha) being the control and (15.00, 20.00 t/ha,) applied before planting of okra seeds. Each okra plant was inoculated with 5,000 larvae of M. incognita. The plants were grown to fruiting stage. The results indicated that application rate of the poultry manure at 15.00 t/ha and 20.00 t/ha and leaf extract of S. alata concentration of 0.60 and 0.80 g/ml significantly (p < 0.05) reduced galling relative to their respective controls. The susceptibility status of the okra cultivar was changed from highly susceptible to resistant in all plants treated with the combination of 0.80 g/ml of leaf extract and 20 t /ha poultry manure. Also, application of the leaf extract alone changed the gall index from 5.00 to 2.00. The best interaction was observed at the application rate of poultry manure at 20 t/ha with 0.60 g/ml leaf extract, where the resistant status was reduced from susceptible (GI=5.00) to resistant (GI=2.25). However, the amended okra plant and application of leaf extract concentration significantly enhanced plant growth, number of leaves, shoot dry weight and root fresh weight accumulation. When 0.60 g/ml of the plant extract was combined with 20 t/ha of the poultry manure, growth and yield of okra plant were highest. The S. alata leaf extract at 0.80 g/ml was phytotoxic as the okra plant showed reduction in growth attributes and pod yield. Therefore, this eco-friendly approach in the management of root –knot disease of okra could be adopted after proper identification of the nematicidal constituents of the leaf extract of S. alata and field trials.