Effect of neem leaf extracts (Azadirachta indica) and synthetic pesticide (Carbofuran) on the root-knot nematode (Meloidogyne spp) of cowpea (Vigna unguiculata L. Walp)
EN Nwankwo, Onuseleogu DC, Ogbonna Confidence U, Okorocha AOE
The nematicidal effect of aqueous Azadirachta indica leaf extract and a standard synthetic nematicide, carbofuran 3G were evaluated for their effect on pathogenicity of Meloidogyne spp on cowpearnand on the growth and yield of cowpea in a screen house. There were ten treatments and a control replicated 3 times in a Completely Randomized Design to give a total of 33 pots. All the pots received the same number of root knot nematode inoculation which was 1000eggs/5mls. The test plant (neem) was applied at five concentrations (100%, 80%, 60%, 40%, 20%) while the carbofuran was applied at five concentrations also (1000mgL-1, 750mgL-1, 500mgL-1 250mgL-1, 100 mgL-1), at the rate of 5ml per treatment. Data on the plant height and number of leaves affected were taken 2 weeks and 4 weeks after inoculation with nematodes while data on other parameters were taken at harvest (60 days after planting). Overall performance of neem in controlling the plant was found to be better than that of carbofuran. At harvest, galling was significantly lower in carbofuran treated plants compared to the neem treated plants. The control plants were most galled with poor yield and had stunted growth. The moderate concentrations of both neem (80%, 60%, and 40%) and carbofuran (750mgL-1, 500mgL-1and 250 mgL-1) performed significantly (P < 0.05) better than control plants in suppressing the effects of root-knot nematode on yield and growth of cowpea. These suggest that the neem leaf extract have nematicidal property and would be effective in the management of root-knot nematodes. Therefore, farmers could adopt it as alternative to carbofuran or other synthetic nematicidal chemicals in controlling root-knot nematode on farmlands.