Abstract：Adopting the indoor virulence measurement method，this paper clarified the toxic effects of 8 chemical agents and Pseudomonas fluorescent YG-1 on Botrytis cinerea；measured the biocompatibility of 8 chemical pesticides and YG-1 strain by plate count method；and screened the optimal ratio of biocontrol strains and chemical agents．The pot experiment verified further the control effect of Pseudomonas fluorescens strain YG-1 and chemical agents on tomato gray mold．The research results showed that among 8 chemical pesticides，boscalid and fludioxonil had a strong virulence effect on Botrytis cinerea，with EC50 value of 0.081 mg · L-1 and 0.075 mg · L-1，respectively．The strain YG-1 has better biocompatibility with boscalid．The optimal ratio of 1.97×108 CFU · mL-1 Pseudomonas fluorescens YG-1 strain and 0.081 mg · L-1 boscalid is 5∶5，and the toxicity ratio for Botrytis cinerea is 1.411 2．The performance is synergistic，and pot control effect reaching 71.31% is extreme significantly higher than that of the single agent．The combination of Pseudomonas fluorescens YG-1 and boscalid has a synergistic control effect on Botrytis cinerea．At the same time，the application of boscalid was reduced by 50%，effectively reducing the usage amount of fungicides．
