UV-B lighting controls powdery mildew in protected strawberry crops and powdery mildew and gray mould in tomatoes.
A new type of UV-B fluorescent lamp, recently developed by the Panasonic Lighting Devices Co., Ltd., Japan, increases disease resistance in strawberry plants to powdery mildew (Sphaerotheca aphani) under greenhouse conditions. In experiments, the number of fruits infected with powdery mildew declined by 84.3% relative to the control treatment (no irradiation). Strawberry plants were irradiated daily with UV-B for 3 h during the night from the time of transplanting to the end of cultivation. It was also found that the incorporation of a UV-B radiation regime can also reduce the required frequency of fungicide application. Under a daily 3 h, UV-B radiation regime, the percentage of powdery mildew infection on strawberry fruits was 0.1%, even when fungicide spraying was greatly reduced when compared to the control. Sugeno, W., Iwasaki, Y. and Hachiya, Y. (2018). Irradiation with UV-B fluorescent bulbs suppresses strawberry powdery mildew. Acta Hortic. 1227, 549-554. DOI: 10.17660/ActaHortic.2018.1227.69
UV-B disease control measures will be found also for other protected crops. A newer compact UV-B fluorescent lamp that provides continuous illumination longer than the previous version, was found to control powdery mildew (Oidium neolycopersici) and gray mould (Botritis cinerea) in tomato plants. Using these lamps control values (suppression) for powdery mildew were over 90% in a 2 year trial, and in the first year, 65.6% against gray mold. Further experiments confirmed that these lamps can induce plant resistance against fungal pathogens. Kanto, T., Watanabe, K., Uchihashi, K., Nishino, M., Sato, F. and Arii, M. (2018). Ultraviolet B radiation from a compact fluorescent lamp for tomato disease control. Acta Hortic. 1207, 197-202. DOI: 10.17660/ActaHortic.2018.1207.26
Image courtesy of Wageningen University and Research. See article on computer fluid dynamics of internal greenhouse environment, entitled Making the Invisible Climate in the Greenhouse Visible. See general article on UV lighting by Digikey. Technical information from Panasonic has been requested on the precise models of lamps utilized.