Mucor rot is caused by the pathogen Mucor piriformis, which can be responsible for severe post-harvest decay in a wide variety of commercially important fruit. There are a minimal number of fungicides that have been shown to be effective against Mucor rot. As a result, alternative methods for control of Mucor rot are currently being investigated. Ultraviolet light in the C spectrum (UV-C) is a germicidal form of radiation that has been demonstrated to kill common post-harvest pathogens. Little information is available for the effectiveness of UV-C light against M. piriformis. For this study, a Far-UV light (222-nm) and a UV-C light (265-nm) were tested for their ability to inactivate M. piriformis. The effects of three UV-C light treatments (0kJ, 10kJ, and 20kJ) were tested on Anjou and Bartlett pears that had been wound inoculated with M. piriformis. Lesion sizes were measured after five weeks in cold storage. The optimal dose required to inactivate M. piriformis in vitro in polystyrene wells with the Far-UV light was found to be 9 kJ, which, with available bulbs set at 8 cm distance, required 17 minutes of treatment. Results showed no significant effect of treatment on final lesion size for both the Far-UV light and the UV-C light. For both lights, final mean lesion sizes were larger for fruit that had been treated with the 20kJ and 10 kJ treatments when compared to the control fruit that received no UV-C treatment. Results from this study suggest that UV-C radiation in the 222-nm and 265-nm light spectrum have minimal impacts on reducing rot caused by M. piriformis in Anjou and Bartlett pears, and, given the duration of treatment required for spore deactivation, this technology may prove impractical for managing M. piriformis on other components of pear packing systems.
