Huanglongbing (HLB) is one of the most devastating diseases of citrus nowadays. The etiological agent is a fastidious and non-culturable bacterium known as
Candidatus
Liberibacter asiaticus (
C
Las).
C
Las is a phloem-restricted pathogen, which makes the efficient delivery of antimicrobial compounds to control it a major challenge for citriculture. Therefore, the development of formulations capable of penetrating plant barriers and reducing the bacterial population within the phloem is critical for the control of HLB. Here we report on the development of a novel formulation loaded with oregano essential oil, hexyl gallate and eugenol, described in the literature as a transdermal permeation enhancer. The most effective formula was selected
in vitro
against bacterial surrogates (
Rhizobium tropici
and
Rhizobium phaseoli
), displaying bactericidal concentrations of 0.25 and 0.5% (v/v), respectively, of bactericidal concentration. The selected formulation was characterized as a near-Newtonian fluid, with 98.5% of particles measuring around 50 nm, a Polydispersity Index of 0.31, and zeta potential of -17.5 mV. Furthermore, Scanning electron microscopy revealed the presence of nanoparticles, alongside microscopic aggregates. The formulation maintained its bactericidal activity over 120-day storage period. During the root-drenching assays, the formulation significantly reduced overall
C
Las titres by 1.29 and 2.46 log
10
over a period of 300 days, in two independent experiments. Furthermore, ecotoxicological assessments revealed no acute toxicity in
Tenebrio molitor
or significant effects in the survival of
Melipona scutellaris
under the tested conditions. Our findings demonstrate the potential of this non-synthetic formulation as an effective and safe alternative for HLB management, without disrupting non-target organisms.