Efficacy of Essential Oils and Their Major Compounds against Meloidogyne graminicola (Rice Root-Knot Nematode) in Pots and Field Trials

Pot experiments of Syzygium aromaticum L. (clove), Cymbopogon,flexuosus L. (lemongrass) and Cymbopogon martinii (Roxb.) Watson (palmarosa) oils and their major metabolites (eugenol, citral and geraniol) based products were carried out for nematicidal activity against M. graminicola (root-knot nematode) at different concentrations (31.5 to 500 ppm) by root dipping method. Results showed that all products tested were found effective in terms of the number of galls per seedling (2.0±0.0 to 3.0±0.57) and seedlings height (14.0±0.02 to 15.15±0.02) recorded compared to controls, in which a number of galls per seedling (4.0±0.56–8.0±0.57) and seedling height (15.20±0.19 to 17.51±0.01) were observed at 500 ppm after 21 days after transplantation in pots using root dip method. Out of six products tested in pot experiments, field trials of three products, based on clove oil, lemongrass oil and palmarosa oil were further carried out at 500 and 1000 ppm by drenching method during 2016–17 and 2017–18 and were compared with carbofuran, a commercial nematicide. Results showed that the heights of the rice seedlings in all the oil treatments at 1000 ppm were at par with carbofuran treatment and better than negative control while the number of galls in palmarosa oil at 1000 ppm and carbofuran was found to be 1.2/plant under field conditions on 30 days after sowing (DAS). This study showed that palmarosa oil could be an alternative to the carbofuran for controlling Meloidogyne graminicola in direct-seeded rice at the nursery level.