Control of blue mold decay of apple during commercial controlled atmosphere storage with yeast antagonists and sodium bicarbonate

A mixture of two yeast antagonists, Metschnikowia pulcherrima and Cryptococcus laurentii, originally isolated from apples and exhibiting greater biocontrol activity against blue mold of apple than either yeast applied alone, were used in combination with sodium bicarbonate (SBC) in a pilot test in which treated fruit were stored under commercial controlled atmosphere (CA) storage conditions. Conidia of Penicillium expansum, antagonists cells and SBC were added to the drench solution. The treatments were applied to apples by drenching entire bins filled with apples containing 100 wounded fruit evenly distributed among five positions in each bin. The treated fruit were stored in commercial CA storages for approximately six months in the 2005–2006 and 2006–2007 storage seasons and then evaluated for incidence of decay. In both years, the treatments with the antagonist alone or in combination with SBC were equally effective and reduced blue mold incidence by 84–97% in 2005–2006 and 73–82% in 2006–2007. SBC alone significantly reduced blue mold incidence compared to the non-treated control but was less effective than the antagonist alone or in combination with SBC. This pilot test showed that the combination of these two antagonists and SBC can be an effective decay control method under commercial CA conditions, confirming results from our earlier laboratory studies using similarly treated fruit stored under CA conditions.