The potential enhancement of Pichia membranifaciens by ammonium molybdate (NH(4)Mo) to control blue mould caused by Penicillium expansum on peach fruit was investigated. Combining P. membranifaciens at 1x10(8) cell/ml with 1 mM NH(4)Mo provided a more effective control of blue mould rot than applying the yeast or NH(4)Mo alone. Addition of 1 mM NH(4)Mo significantly increased the growth of P. membranifaciens in peach wounds, but did not affect the population in nutrient yeast dextrose broth medium. The in vitro experiment showed that the combined treatment inhibited spore germination and germ tube elongation of P. expansum in comparison with the treatment of P. membranifaciens or NH(4)Mo alone. Moreover, P. membranifaciens, NH(4)Mo, and the combination of them did not impair the quality parameters including fruit firmness and content of total soluble solids, titratable acidity and vitamin C of peach fruit after 6 days of storage at 20 degrees C. These results suggested that the use of NH(4)Mo is a useful approach to improve the efficacy of P. membranifaciens for postharvest disease control in peach fruit.