Determining the Nematicidal Effects of Some Plant Extracts on Egg Hatchability and Control of Meloidogyne spp. in Cowpea [Vigna unguiculata (L.) Walp]

The Current investigation was undertaken to evaluate the nematicidal activity of five plant species: Luffa cylindrica (Linn) MJ Roem, Momordica charantia Linn, Euphorbia hirta Linn, D. scorpiurus (Sw.) Desv. and Starchytarpheta cayennensis L.C. Rich (Schau), wood ash and a synthetic insecticide (L. cyhalothrin) on egg hatachability and control of Meloidogyne spp. in cowpea. The effects of five test plants (Luffa cylindrica, Momordica charantia, Euphorbia hirta, Desmodium scorpiurus, and Stachytarpheta cayennensis), wood ash from Gmelina aborea, a synthetic insecticide (Karate-Lambda cyhalothrin), and untreated tap water (control) were assessed against the egg hatchability and control of Meloidogyne spp. in cowpea (Vigna unguiculata (L.) Walp) in the laboratory and greenhouse. The experiments were laid out in a Completely Randomized Design (CRD) with 13 treatments (Hot water extracts (HWE) and cold water extracts (CWE) of L. cyclindrica; E. hirta, D. scorpiurus, S. cayennesis, M. charantia, wood ash, L. cyhalothrin and control) replicated 3 times. The result of the laboratory experiment showed that the hot and cold water extracts of L. cylindrica and HWE of M. charantia significantly (p < 0.05) inhibited the hatching of nematode eggs. Results obtained from the Greenhouse indicated that HWE of E. hirta, CWE of S. cayennesis, CWE and HWE of L. cylindrica significantly improved cowpea yield, (p< 0.05). The aqueous extracts reduced the number of galls on the roots, nematode populations in the root and soil. The results obtained G. aborea extracts did not differ significantly with the synthetic nematicide – L. cyhalothrin. The leaf extracts of the test plants have potential as sources of botanical nematicides to reduce the devastating effects of plant-parasitic nematodes in cowpea fields. There is need for further study especially in the area of nematode population density that could cause significant damage. Also, the effectiveness of plant extracts in a field environment should also be assessed.