Development and evaluation of eco-friendly carvacrol nanoemulsion as a sustainable biopesticide against bacterial leaf blight of cluster bean.

Background: The study of carvacrol plant antibacterial components has recently become a hot topic in modern farming. Carvacrol industrial applications are restricted by their physicochemical instability and partial solubility in water. In the present study, an ultrasonic emulsification method was used to prepare a carvacrol nanoemulsion (CAR-NE) employing nonionic surfactants. The CAR-NE was characterized using a dynamic light scattering (DLS) instrument and transmission electron microscopy (TEM). The goal of this work was nanoencapsulation of carvacrol to improve its aqueous solubility and preservation of the encapsulated compound against climatic conditions. Another aim of the present study was the evaluation of the growth-promoting effects and antibacterial potential of CAR-NE against bacterial leaf blight of cluster bean.

Results: CAR-NE showed a hydrodynamic diameter, ZP and PDI index of 43.88 ± 4.30 nm, -47.8 ± 0.23 mV and 0.246 ± 0.04, respectively. The spherical shape morphology of CAR-NE was confirmed by TEM imaging. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) of the CAR-NE were 20 and 160 μL mL (respectively) against Xanthomonas axonopodis pv. cyamopsidis. Additionally, the antibacterial potential of CAR-NE was evaluated for controlling bacterial blight of cluster bean in fields. The disease severity in the negative control plants (water) was 84%, but that in the CAR-NE 160 (μL mL ) was remarkably low at 14%, nearly the same as the positive control (streptomycin sulfate).

Conclusion: The shelf-life of CAR-NE was 2 months at room temperature without any appreciable changes in hydrodynamic diameter and zeta potential. Consequently, plants treated with CAR-NE 160 showed substantial improvement in plant growth. © 2023 Society of Chemical Industry.