Evaluation of different leaf extracts of Melia azedarach formulations on root-knot nematode, Meloidogyne incognita, infesting tomato plant in vitro and in vivo

The bioactive, eco-friendly nematicides found in plant extracts with nematicidal activity on Meloidogyne spp . contribute to decreasing crop damage caused by root-knot nematodes, which are one of the gravest risks to human health and the environment. The present study investigated the nematicidal potential of solvent extracts obtained from Melia azedarach leaves, formulated as emulsifiable concentrates (EC) and oil-in-water emulsions (EW) using eco-friendly solvents and surfactants. The crude extracts were analyzed through phytochemical qualitative tests and gas chromatography-mass spectrometry (GC-MS), which identified notable quantities of eight terpenoids, including phytol (2-hexadecen-1-ol) 17.33 %, neophytadiene 12.91 %, 3,7,11,15-tetramethylhexadecenol 20.59 %, and 1,2-benzendicarboxylic acid mono(2-ethylhexyl 32.22 %. Additionally, the compositions included steroids such as gamma-sitosterol 2.30 %, long-chain fatty acid hexadecanoic acid 14.31 %, and two flavonoids, wogonin methyl ether 4.69 % and lupinifolin 5.77 %, all recognized for their nematicidal properties. Both formulations (EC and EW) demonstrated high stability across diverse storage conditions in all physical properties, such as viscosity, surface tension, density, and flash point, with good limitations for spray solutions such as foam, emulsion stability, conductivity, and pH. In vitro assessments of nematicidal activity indicated that the EC formulation was more effective against the second-stage juveniles (J2) of M. incognita than the EW formulation of the same extracts. In particular, the LH10 % EC formulation exhibited the highest nematicidal toxicity, with an LC 50 value of 47.95 μg ml −1 after 48 hours of exposure. Pot experiments further showed that all treatments significantly reduced nematode infections compared to untreated controls. Notably, both hexane extract formulations, LH10 % EC and LH10 % EW, achieved the greatest reductions in tomato root galls (93.75 % and 87.5 %, respectively) and J 2 hatching in soil (56.07 % and 54.78 %, respectively). Additionally, all treatments improved the growth parameters of tomato plants compared to untreated controls. These findings highlight the potential of eco-friendly materials in nematode management programs as a sustainable alternative to conventional chemical nematicides.