Variation in Growth, Morphology, and Fungicide Sensitivity Among Monilinia Species from South Tyrol’s Alpine Orchards

Brown rot, caused by <i>Monilinia</i> species, is a major disease affecting stone and pome fruits. The most relevant species are <i>M. fructigena</i>, <i>M. laxa</i>, <i>M. polystroma</i>, and <i>M. fructicola</i>. These four species exhibit morphological differences, but comparative data on these traits remain limited. In European integrated fruit production, pre-harvest control of brown rot mainly relies on the fungicides cyprodinil, boscalid, and tebuconazole. Given the coexistence of multiple <i>Monilinia</i> species, understanding differences in fungicide sensitivity is crucial for optimizing control strategies. In this study, mycelial growth, colony and conidial morphology, and sporulation capacity on potato dextrose agar (PDA), tomato sauce agar (TSA), and apple fruit were investigated. Fungicide sensitivity was assessed by measuring mycelial growth on apples following treatment with the three active ingredients. Tebuconazole was the most effective fungicide, particularly against <i>M. laxa</i> and <i>M. polystroma</i>, while cyprodinil and boscalid were less effective. These results highlight the need for species-specific fungicide strategies, <i>Monilinia</i> populations, and the effectiveness of disease control under various environmental conditions. All <i>Monilinia</i> species sporulated successfully on TSA, underscoring its suitability for sporulation studies. Conidial size varied significantly among species; nevertheless, overlapping sizes prevent reliable species or strain discrimination based on this trait alone.