Nano-emulsion of garlic oil extracts: development, characterization and nematicidal efficacy against Meloidogyne incognita on tomato

The root-knot nematode, Meloidogyne incognita, causes serious economic losses in agricultural production worldwide. Although traditional nematicides have proven effective, their utility is becoming increasingly restricted by regulations due to risks to ecosystems and public health. Consequently, plant-based extracts are gaining popularity as an eco-friendly alternative for nematode control. However, the‍‌‍‍‌ limitations of using plant extracts necessitate the development of novel ‍‌‍‍‌formulations. Therefore, garlic oil was extracted with ethanol or ethyl acetate and analyzed for composition by GC-MS. It was developed as a nanoemulsion, characterized and then tested for use as an alternative strategy to manage M. incognita infecting tomato plants. The results showed that garlic oil extracted with ethanol contained a high concentration of bis-(2-diethyl aminoethyl) trisulfide (23.74%), methyl propyl tetrasulfide (18.85%), and isopropyl tert-butyl disulfide (10.93%). 1,3-dipentyltrisulfane (74.18%) and 2,4-dimethylphenyl 2-naphthyl sulfone (15.52%) were the main constituents in garlic oil extracted with ethyl acetate. The resulting six nanoemulsion formulations were prepared using the high-energy emulsification method and were characterized by tiny droplets (≤ 138 nm), the polydispersity index (PDI) (≤ 0.65), zeta potential values in the range of 10.2-20.3 mV, and spherical morphology. These formulations maintained stable for 16 weeks when stored at 25 °C. Meanwhile, soil drenching with the nanoemulsions effectively managed M. incognita by reducing the formation of root galls and 2nd juveniles in the soil and promoting tomato growth, particularly the Tween 20 and Tween 80 formulations, both of which were ethanol-based and demonstrated superior nematicidal effects compared to ethyl acetate extract as well as the tested nematicides; cadusafos and oxamyl. Overall, the garlic oil nanoemulsion formulations developed in our study appear to be promising candidates for the development of novel and green nematicide formulations for managing M. incognita associated with tomatoes in sustainable agriculture.