Nematicidal Potential of some Essential Oils Applied as soil Drench or Foliar Spray against Root-Knot Nematode, Meloidogyne incognita Infecting Eggplant under Greenhouse Conditions.

Root knot nematode, Meloidogyne incognita is the most serious threat affecting eggplant, Solanum melongena L. This study aimed to evaluate the efficiency of essential oils of four plant species (as soil drench/or foliar spray) individually or in integration with oxamyl against M. incognita infecting eggplant under greenhouse conditions. Soil drench application of essential oils in eggplant revealed species-specific efficacy and physiological impacts. Peppermint oil emerged as the premier treatment, reducing J2s densities by 85.29% (347 vs. 2358.25 J2s/250ml soil in control) and egg masses by 86.37% - narrowing the gap with oxamyl (96.14% J2s reduction) to just 9.77 percentage points. Garlic oil showed moderate efficacy (53.59% J2s reduction, 78.97% egg mass suppression). In infected plants, dill oil executed extraordinary photosynthetic rescue, elevating chlorophyll by 206.25% while preserving flavonoids (−15.07%). Foliar spray of essential oils on eggplant under identical conditions yielded distinct efficacy against M. incognita. Chili pepper oil dominated other treatments, reducing J2s by 80.66% (456.2 J2s/pot) and egg masses by 90.45% (22.25 vs. 233.0). Dill oil enabled systemic resilience in infected plants, recovering 68.8% of loss (49.38cm length) and increasing leaf counts by 82.35%. Biochemically, chili oil boosted chlorophyll by 145.83% in infected plants but incurred significant polyphenol depletion (−34.82%). Oxamyl treatment surpassed all tested applications in suppressing nematode population, number of galls and egg masses. A synergistic interaction was recovered with the integration of peppermint + Oxamyl (94.4% J2 reduction) followed by garlic + Oxamyl (89.1% J2 reduction) compared to essential oils single application.