Anthracnose, caused by Colletotrichum spp., is a major constraint in chili production and can result in substantial yield losses. This study aimed to identify the causal pathogen of anthracnose and evaluate a nanoencapsulated botanical pesticide based on an essential oil consortium for controlling the pathogen. The study comprised pathogen identification, formulation using different nanoemulsion-to-matrix ratios, physicochemical characterization, and in vitro antifungal evaluation. Morphological, pathogenicity, and molecular analyses identified Colletotrichum scovillei as the causal agent of anthracnose, with sequence similarity of up to 100% to reference sequences in GenBank. Among the tested formulations, Formula B (nanoemulsion-to-matrix ratio of 6:1) exhibited the lowest polydispersity index (PDI) of 0.488, indicating a comparatively narrower particle-size distribution among the formulations. Its Z-average particle size was 363.0 nm, with a zeta potential of −35.0 mV, indicating relatively good electrostatic stability. In vitro assays demonstrated that the nanoencapsulated essential oil consortium inhibited the growth of C. scovillei, although its efficacy varied among formulations and observation periods and remained lower than that of the synthetic fungicide. The inhibitory activity of the nanoformulations varied among formulations and generally decreased over the 14-day observation period. These findings indicate the potential of nanoencapsulated essential oil formulations as a botanical approach for suppressing C. scovillei. Further studies under storage and field conditions are required to evaluate formulation stability, persistence of antifungal activity, application rates, and practical efficacy.
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