NEMATICIDAL POTENTIAL OF EXTRACTS OF NEEM (Azadirachta indica) AND LEMON GRASS (Cymbopogon citratus) ON ROOT-KNOT NEMATODES (Meloidogyne spp) INFECTING SWEET POTATO

Abstract

The nematicidal potential of extracts of Azadirachta indica (neem) leaves and Cymbopogon citratus (lemon grass) on root-knot nematodes infecting sweet potato was evaluated between the months of June and November, 2012 at the Botanical Nursery of the University of Jos. The root-knot nematodes were obtained from galled roots of tomato and potato in Jos farms. A total of forty (40) sweet potato cultivar TIS 87/0087 were raised in steam-sterilized soil in clay pots and used for the study. Thirty (30) of the test plants were inoculated with 2250 juveniles of root-knot nematodes each while 10 were not inoculated serving as positive control. Ten of the inoculated plants were treated with extracts of neem leaves, 10 were treated with extracts of lemon grass while 10 were not treated, they served as negative control. Growth and yield parameters were then measured from 42 days after planting to 120 DAP using agronomic traits as a measure of growth and yield. Growth and yield parameters such as number of leaves, length of vines, number of tubers, weight of tubers etc were highest in the positive control, followed by sweet potato infected with nematodes and treated with lemon grass extract, then those treated with Neem leaves extract while those not treated with extract had the least growth and yield. Statistical analysis showed that the positive control produced significantly higher (P˂ 0.05) growth and yield parameters than all the other treatments. Infected plants treated with the extracts were also found to have significantly higher growth and yield parameters than the plants that were infected but not treated with extracts (negative control) at 0.05 level of probability. Number of galls was highest among the plants from the negative control, followed by plants treated with lemon grass extracts. The findings indicated that extracts of Lemon grass and Neem leaves improved growth and yield data of nematodes infected sweet potato and thus could be utilized in the control of root-knot nematodes in gardens