Effect of plant eztracts and essential oils on root-knot nematode

Abstract

The nematicidal activity of methanolic extracts (20 µg ml-1) from twenty Jordanian plant species against two species of root-knot nematodes in vitro was evaluated. Whole-plant extract of Hypericum androsaemum showed the highest activity (11% mortality) against Meloidogyne javanica after 24 h of incubation. However, leaf extract of Origanum syriacum also increased M. javanica mortality markedly a day later, reaching 59 and 82% after 48 and 72 h of exposure respectively. Against M. incognita the response of leaf extracts was somewhat different, with leaf extract of Artemisia herba alba the most effective causing 22, 51, 54% mortality after 24, 48 and 72 h of exposure respectively. With a tenfold concentration (200 µg ml-1) of those plant extracts thought to contain volatile oils, the secondstage juveniles (J2) mortality of both nematodes increased after 24 and 72 h of incubation. Nematicidal tests of some volatile oils that are active ingredients of the plants tested revealed that geraniol, thymol, and camphor were the most effective against M. javanica J2s, with 91, 60, 56% mortality respectively after 72 h of exposure. Cineole, menthol, and pinene were not effective against this nematode. Against M. incognita J2s, the most effective oil components were carvacol, thymol, and geraniol, with mortalities of 100, 90, and 74% respectively after 72 h of exposure. Cineole was the least effective against M. incognita.