Nematicidal potential of some indigenous plant extracts against root-knot nematode on cacao

The effect extract of Ocimum gratisimum L., Carica papaya, Azadirachta indica A. Juss, Vernonia amygdalina and Bixa orellana L. on pathogenicity and reproduction of Meloidogyne incognita race 3, the causal organism of the root-knot disease of cacao was investigated in the greenhouse. Leaf extracts were prepared by blending and filtration of 25g of chopped leaves in 100ml of distilled water. Each cocoa seedling in a naturally infested soil received 40ml water extract of the leaves. Nematode populations were reduced by the application of the extracts in a descending order of A. indica, B. orellana, O. gratissimum, C. papaya and V. amygdalina. Plant vigour was enhanced based on the treatments compared to the control. The significance of these findings is discussed in relation to the non-synthetic chemical means of disease control on cacao and use by the resource-poor farmers in Nigeria.