Toxicity of essential oils extracted from Corymbia citriodora and Eucalyptus camaldulensis leaves against Meloidogyne incognita under laboratory conditions

Essential oils (EOs) were extracted from Corymbia citriodora and Eucalyptus camaldulensis fresh leaves and tested for their nematicidal activity at four different concentrations viz., 125, 250, 500 and 1000 mg/l against root-knot nematode, Meloidogyne incognita under laboratory conditions. All concentrations significantly inhibited egg hatching (31.24–66.35%) and mortality of second stage juvenile. Inhibition of egg hatching (%) and mortality (%) of J_2 were increased linearly with increasing concentration of EOs. Corymbia citriodora EO was more effective than E. camaldulensis in inhibiting egg hatchability and suppressing J_2 viability. Probit analysis results showed median inhibitory concentration (IC_50) values of 412.7 and 615.9 mg/l for C. citriodora and E. camaldulensis leaves EOs, respectively. In addition, the lethal concentrations (LC) causing 50% J_2 mortality (LC_50) of C. citriodora and E. camaldulensis oils were 235.9 and 327.7 mg/l, for C. citriodora and E. camaldulensis leaves EOs, respectively. Essetial oils were analyzed by gas chromatography-mass spectrometry (GC-MS). Isopulegol (53.68%), citronellol (15.26%) and isopulegol acetate (15.25%) were found to be major constituents of C. citriodora, while eucalyptol (55.36%) and α-pinene (14.87%) were the major components of E. camaldulensis leaves EO. Because of the high nematicidal performance of studied EOs, further trials are required to investigate their efficacy in controlling nematode infection and to use them as alternatives to synthetic nematicides in integrated nematode management.