Evaluation of various plant extracts for their nematicidal efficacies against juveniles of Meloidogyne incognita

Twenty-seven different samples that included various plant components (leaves, fruits, and stems) were collected from 21 tree and herbal species in 19 genera from Gezira locality, Sudan. Methanol or hexane extracts of the 27 samples were screened for nematicidal activity against second-stage juveniles of Meloidogyne incognita in the laboratory. The juveniles were exposed to 500 ppm of each plant extract for 24, 48 and 72 h. Five plant extracts exhibited highly promising mortality rates of 95-99% after 72 h of exposure, which were statistically different from the other extracts. These extracts were from Dinbera retroflexa (leaves), Cucumis melo var. agrestis (fruits), Eucalyptus microtheca (leaves), Acacia nilotica (pods), and Chenopodium album (leaves). Six extracts derived from the leaves of Solenostemma argel, Aristolochia bracteolate, and Ziziphus spina-christi and the seeds of Aregimone mexicana, Datura stramonium, and Azadirachta indica produced relatively high mortality rates of 94-80% after 72 h of exposure. The 5 most nematicidal plant extracts listed above were further screened against similar stage juveniles of the nematode species using only 50 ppm for 24, 48, and 72 h. Three plant extracts, C. melo var agrestis (fruits), A. nilotica (fruits), and C. album (leaves), exhibited 41, 42 and 45% mortality rates, respectively. The mortality rate increased with increasing exposure time for most of the extracts.