Preparation of Salicylic Acid and Berberine Co-loaded Chitosan Nanocarriers and Their Efficacy in Preventing and Treating <i>Panax ginseng</i> Black Spot Disease

To address issues of pesticide resistance and environmental pollution in chemical control of ginseng black spot (caused by Alternaria panax) and unstable efficacy of traditional biological control, this study developed chitosan nanoparticles (CSNPs) co-loaded with antimicrobial berberine (BR) and immune-activating salicylic acid (SA), referred to as BR/SA@CSNPs based on the Traditional Chinese Medicine theory of "eliminating pathogens and reinforcing vital qi" (Qu Xie Fu Zheng), aiming to simultaneously suppress pathogens and activate plant resistance. BR/SA@CSNPs were prepared via optimized ionic cross-linking, with physicochemical properties and stability characterized. Efficacy was evaluated through in vitro antifungal activity (EC₅₀) and ginseng antioxidant enzyme activity assays. Optimized BR/SA@CSNPs exhibited uniform particle size (162.4 ± 2.5 nm), good dispersity (PDI = 0.149 ± 0.041), environmental stability, and pH-responsive release. In vitro assays demonstrated significant pathogen inhibition (EC₅₀ = 55.28 μg/mL), mycelial membrane disruption, and induction of oxidative damage. In vivo tests showed that BR/SA@CSNPs induced ginseng to activated antioxidant enzymes and suppressed lipid peroxidation. BR/SA@CSNPs successfully integrated the "eliminating pathogens and reinforcing vital qi" theory: BR directly suppressed pathogens (eliminating pathogens), SA activated SAR to enhance resistance (reinforcing vital qi), and the multifunctional CS carrier provided synergistic effects, offering a novel strategy for efficient and green nano-pesticide control of ginseng black spot.