Lippia gracilis Schauer essential oil nanoformulation prototype for the control of Thielaviopis paradoxa

The goal of the study was to evaluate the antifugal effect of essentials oils from the Lippia gracilis genotypes with main components of thymol and carvacrol and essential oil emulsions on Thielaviopis paradoxa. The essential oil was extracted from the genotypes by hydrodistillation. The nanoemulsions were obtained from the spontaneous emulsification technique. The nanoemulsions obtained where characterized by particle size, zeta potential and polydispersity. For the fungal activity bioasssays in vitro, the essential oils, majority components and nanoemulsions in different concentrations were added to potato-dextrose-agar (PDA) medium. Each plate was inoculated placing at the center a 7 mm disk containing T. paradoxa mycelium. For the in vivo assay, for the plant infections a 2 × 106 CFU (colony forming unit) suspension in was use in PDA medium. After 7 days, the emulsions were pulverized with minimal inhibitory concentrations and testemonies. The ecophysiology parameters (photosynthesis; stomatal conductance, transpiration and vapor pressure deficit between plant and air) in 30 coconut trees inoculated with T. paradoxa was analyzed. The L. gracilis essential oil has antifungal potential for the control of coconut tree stem-bleeding, since the T. paradoxa was inhibited in all concentrations used. The genotype LGRA109 essential oil presented MIC of 0.23 mg/mL, while the LGRA106 presented MIC of 0.82 mg/mL. The essential oil nanoemulsions presented high efficiency in disease control (MIC 0.6 mg/mL) and low phytotoxicity; therefore representing a good alternative for the efficient control of T. paradoxa in coconut tree.