Preharvest application of antagonistic yeasts for the control of fungal pathogens in organic peach and plum orchards

BACKGROUND The control of fungal diseases in organic fruit production remains a major challenge due to the limited availability of authorized phytosanitary tools. This study evaluates the efficacy of two antagonistic yeasts – Metschnikowia pulcherrima L672 and Hanseniaspora uvarum L793 – in organic peach ( Prunus persica ) and plum ( Prunus salicina ) orchards over two consecutive seasons. Four treatments were compared: an untreated control, a standard organic management program, and foliar applications of each yeast strain. RESULTS Microbiological monitoring revealed that Metschnikowia pulcherrima L672 demonstrated superior persistence and colonization, significantly reducing the abundance and colony size of filamentous fungi, including key pathogenic genera such as Alternaria , Cladosporium , and Penicillium spp. This biocontrol effect translated into improved fruit quality, notably a significant reduction in discarded plums at harvest, without compromising overall yield. In contrast, H. uvarum L793 exhibited limited persistence and a more transient antagonistic effect. CONCLUSION These findings support the integration of Metschnikowia pulcherrima L672 as a promising and effective biocontrol agent for managing fungal diseases in organic stone fruit production systems.