Abstract:

The feasibility of the combination of chemical fungicides and biological fungicides to control tomato gray mold was explored to deal with the contradiction between the enhancement of fungicide resistance and the demand for pesticide reduction in the chemical control of tomato gray mold. The best combination scheme of Bacillus amyloliquefaciens and fludioxonil was determined by individual virulence determination, compatibility analysis and compound screening, and the control effect was verified by in vitro fruit and pot experiment. The results revealed that fludioxonil demonstrated the highest virulence against Botrytis cinerea (EC₅₀=0.0889μg/mL), while B. amyloliquefaciens showed strongest antifungal activity (EC₅₀=0.5940μg/mL), with good mutual compatibility preserved (even at 1500μg/mL fludioxonil, B. amyloliquefaciens viable cells remained at10.8×10⁸ CFU/mL). When compounded at their respective EC₅₀ values, the 7:3 (v/v) ratio exhibited the highest pathogen inhibition rate, with a virulenceratio of 1.81 and an inhibition rate of 90.81%, showing a significant synergistic effect. At registered label-recommended concentrations, the preventive and therapeutic effects of the mixture on detached fruits were 82.62% and 64.56%, while greenhouse pot trials recorded 75.23% and 74.24%, respectively, both significantly superior to single-agent treatments, and with a 30% reduction in fludioxonil amount. These findings indicate that the 7:3 (v/v) combination of fludioxonil and B. amyloliquefaciens at registered concentrations provides a highly effective, synergistic, and environmentally friendly strategy for managing tomato gray mold.

Key words: Bacillus amyloliquefaciens, fludioxonil, tomato gray mold, virulence determination, combined virulence, compound synergistic effect, pathogen inhibition rate, control efficacy