Synergistic suppression of Pestalotiopsis versicolor by acetic and gallic acids: a reduced‐risk strategy for integrated management of bayberry twig blight

BACKGROUND Bayberry ( Myrica rubra ) twig blight, caused by Pestalotiopsis versicolor , threatens sustainable production across southern China. Current management relies heavily on synthetic fungicides (e.g. prochloraz, propiconazole), which face increasing regulatory restrictions owing to environmental and health concerns. Reduced‐risk alternatives compatible with integrated pest management (IPM) are urgently needed. RESULTS Through a three‐criteria screen of bayberry rhizosphere metabolites by detection frequency, water solubility, and antifungal activity, acetic acid (AA) and gallic acid (GA) were prioritized from 10 candidates. A 1:2.5 mixture of 1 mg mL −1 AA and 2.5 mg mL −1 GA exhibited clear synergy (synergistic ratio 1.68), inhibiting P. versicolor mycelial growth by 87% and spore germination completely. The combination induced rapid membrane disruption, with relative electrolyte leakage reaching 97.8% at 2 h and malondialdehyde content increasing 6.4‐fold. In glasshouse trials, the formulation provided 58.0% preventive and 53.8% curative control, achieving ≈70% of propiconazole efficacy at one‐tenth of the dose. CONCLUSION The AA–GA combination represents a viable reduced‐risk fungicide for IPM programs in bayberry production. This plant‐derived formulation offers 90% chemical load reduction and minimal resistance risk for sustainable disease management.