Two separate but identical greenhouse trials were conducted to investigate the effects of extracts of leaves and roots of Leucaena leucocephala and Gliricidia sepium each at 80,000 mg / kg and 40,000 mg / kg on Meloidogyne incognita on okra. Each potted nine-day old okra seedling was inoculated with 3,000 fresh eggs of M. incognita and 5ml of each of the extracts was added simultaneously around the roots of the seedling. Treatment of okra plant with L. leucocephala and G. sepium extracts resulted in reduced nematode population, reduced galling, reduced nematode reproduction rate and enhanced fruit weight. Chemical analysis revealed that G. sepium leaves contained phenolic compound and carboxylic acid, while the roots showed the presence of aromatic amide, phenolic compound and carboxylic acid. L. leucocephala leaves showed the presence of phenolic compound, aromatic amide and carboxylic acid, while the roots showed the presence of phenolic compound and carboxylic acid. The results of this study suggest that leaf and root extracts of L. leucocephala and G. sepium at the rate of 40,000 mg / kg could be useful in root knot nematode management in vegetable beds

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Essential oils are natural volatile substances found in a variety of plants. The toxicity of z-β-ocimene and dihydrotagetone (isolated from the oil of Tagetes minuta) to eggs and juveniles of Meloidogyne incognita was investigated in vitro. Tagetes minuta oil at 4%, 3%, 2% and 1% was strongly toxic to eggs and juveniles of M. incognita. Further studies revealed that dihydrotagetone and z-β-ocimene isolated from the oil showed strong nematicidal activity against M. incognita, with dihydrotagetone showing a higher level of toxicity than z-β-ocimene. The results of this study suggest that dihydrotagetone and z-β-ocimene isolated from T. minuta oil are potential sources of botanicals for control of the root-knot nematode M. incognita.

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