Eucalyptus (Eucalyptus camaldulensis) and chinaberry (Melia azedarach) extracts' potential for sustainable control of root-knot nematode, Meloidogyne javanica

Root-knot nematode has a widespread distribution and has caused significant damage, as in some cases, led to complete crop loss. Environment-friendly and safe methods are essential for the replacement of chemical nematicides. In the present study, the lethal effect of aqueous extracts from eucalyptus (Eucalyptus camaldulensis) and chinaberry (Melia azedarach), which are locally available plants, on second-stage juveniles (J2) of the root-knot nematode, Meloidogyne javanica was investigated under laboratory conditions. For this purpose, concentrations of 1000 to 7000 ppm were evaluated on 100 numbers of J2 at two different time intervals, two four days, using a factorial experiment (concentrations of 1000 to 7000 and times of two and four days after extract exposure) within a completely randomized design with three replications. The median lethal concentrations (LC50) for each extract were calculated. The results of this study indicate a significant correlation between the increased mortality rate of juveniles and the concentration and exposure period. The highest concentration exhibited the best results after four days, with mortality rates of 73% and 68% for M. azedarach and E. camaldulensis compared to the control, respectively. The probit analysis revealed that LC50 values were 5044 and 5694 ppm for chinaberry and eucalyptus, respectively. No significant changes were recorded in the internal organs of the dead larvae, except for the contraction in parts of the intestine and their straight standing. In general, plant extracts present a promising method for managing M. javanica.