Synergism of citral from Cymbopogon citratus essential oil and undecan-2-one against Meloidogyne incognita

The nematicidal activity of the essential oil of Cymbopogon citratus and its main components were studied. During in vitro assays with Meloidogyne incognita second-stage juveniles (J2), the oil showed an LC50 of 166 μg ml−1. In vivo assays that exposed J2 to the LC50 oil concentration significantly reduced galls and eggs on tomato roots. According to gas chromatography-mass spectrometry analyses, the main components of the essential oil were geranial (42.7%) and neral (33.0%). The combination of these two isomers, known as citral, had an enhanced nematicidal activity at low concentrations as shown by in vitro tests through a synergistic interaction with undecan-2-one. In assays with tomato plants inoculated with M. incognita J2, the combination of citral (600 μg ml−1) and undecan-2-one (300 μg ml−1) showed a high reduction in the number of galls (63.4%) and eggs (56.3%) in relation to Tween 80® control. The citral/undecan-2-one combination showed a synergistic nematicidal activity against M. incognita during in vitro and in vivo assays.