Aim: To improve the efficacy of Candida sake by adding ammonium molybdate to control post-harvest decay in Golden Delicious apples. Methods and Results: In laboratory trials, C. sake 2 x 10(6) cfu ml(-1) plus 5 mmol l(-1) ammonium molybdate greatly reduced Penicillium expansum , Botrytis cinerea or Rhizopus stolonifer in apples stored at 20degreesC for 7 days, and reduced by more than 90% blue and grey mould in apples stored at 1degreesC for 60 days. The consistency of these results was maintained in semi-commercial trials at 1degreesC in air and in a low oxygen atmosphere for 120 days. The pre-harvest application of C. sake 2 x 10(7) cfu ml(-1) plus 1 mmol l(-1) ammonium molybdate did not improve post-harvest biocontrol of blue mould. The population of C. sake significantly decreased in the presence of ammonium molybdate in apple wounds. Conclusion: The addition of ammonium molybdate at 5 mmol l(-1) to C. sake enhanced the efficacy of the antagonist to control post-harvest diseases on apples. Significance and Impact of the Study: Ammonium molybdate significantly reduces the amount of C. sake biomass required to achieve post-harvest disease control, with a consequent reduction in costs. This may be useful in the industrial production of C. sake .