Integrating heat treatment, biocontrol and sodium bicarbonate to reduce postharvest decay of apple caused by Colletotrichum acutatum and Penicillium expansum

The Golden Delicious apples were wound inoculated with conidial suspensions of either Colletotrichum acutatum or Penicillium expansum, then treated with heat (38 .C)for 4 days, sodium bicarbonate, and/or one of two heat tolerant biocontrol agents (yeasts). Following four months storage at 0 .C, the apples were left at room temperature for two weeks. Populations of antagonists were stable throughout the experiment and were higher on the heated than the non-heated fruit. Both antagonists reduced decay caused by P. expansum, whereas heat or heat in combination with either antagonist eliminated decay. Either heat or the antagonists alone reduced decay caused by C. acutatum, but a combination of the two was required to completely eliminate decay caused by this pathogen. Adding sodium bicarbonate to the heated or antagonist-treated fruit had little effect on decay caused by either pathogen but when used on non-heated fruit, it significantly reduced decay severity caused by P. expansum after four months at 0 .C. The goal of this research is to combine alternative methods of control to provide an effective substitute for synthetic pesticides.