UV-C treatment has a higher efficacy on reducing germination of spores rather than mycelium growth

Abstract For ecological reasons, effective alternatives should be found to control plant diseases on crops. UV-C is a highly energetic radiation with a disinfecting effect on different microorganisms. This study investigated the effect of UV-C treatment on the vegetative and reproductive growth of Fusarium culmorum , Alternaria spp., Botrytis cinerea , Sclerotinia sclerotiorum and the biocontrol agent Trichoderma asperellum . All fungal species were grown on agar plates and treated with different UV-C doses (0.015–1.57 kJ/m 2 ). Mycelium diameter, spore production, and germination of these spores were analyzed. In a second experiment, a spore suspension was treated with different UV-C doses (0.015–1.57 kJ/m 2 ), and germinated spores were counted 1, 2, and 3 days after UV-C treatment. The results indicate that mycelium growth was slightly reduced. However, the mycelium began to recover after the first day. Furthermore, no complete cessation of mycelium growth could be detected. Increasing UV-C doses resulted in reduced spore germination. On the first day after UV-C treatment, spores treated with the highest dose of 1.57 kJ/m 2 did not germinate. However, germination increased as the time between treatment and measurement increased. The treated fungal species reacted differently to UV-C treatment. F. culmorum reacted most sensitively to mycelium treatment. T. asperellum had the highest level of sensitivity to the spore treatment, followed by F. culmorum , Alternaria spp., and B. cinerea . The developmental stage of the fungus is crucial for the success of the UV-C treatment and should be taken into account when using this plant protection technology.