Potential for far ultraviolet (UV) 220 nm light for management of strawberry fungal pathogens

Authors: Janisiewicz, Wojciech; Takeda, Fumiomi; Evans, Breyn; Camp, Mary

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2021
Publication Date: 8/10/2021
Citation: Janisiewicz, W.J., Takeda, F., Evans, B.E., Camp, M.J. 2021. Potential for far ultraviolet (UV) 220 nm light for management of strawberry fungal pathogens. Crop Protection. https://doi.org/10.1016/j.cropro.2021.105791.
DOI: https://doi.org/10.1016/j.cropro.2021.105791

Interpretive Summary: Fungal pathogens that cause fruit and plant diseases are developed resistance to many of commercial fungicides. A more sustainable alternative to synthetic pesticides for control of pre- and postharvest diseases of fruit crops is desirable. Recently developed night-time ultraviolet (UV) light treatment provided a breakthrough for managing disease-causing fungi, but there is still a need to develop a UV technology that can be used day or night without any negative effect on plants. In this study, we evaluated the 222 nm far UV irradiation lamp on nine types of fungal pathogens of strawberry. The results of this study clearly showed the superiority of 222 nm lamps over the conventional 254 nm lamp. The pathogens could be killed with much shorter exposure time with far UV lamp, and they were killed with daytime irradiation as good as night-time applications.

Technical Abstract: Recently developed night-time irradiation provided the breakthrough that made ultraviolet (UV) technology with 254 nm (UV-C) commercially feasible as a sustainable alternative to synthetic fungicides for control of pre- and postharvest diseases of fruit crops. To make UV technology more efficient, we explored the effectiveness of far UV (222 nm) produced by a Krypton-Chlorine excimer lamp to kill several major fungal pathogens of strawberry such as B. cinerea, P. expansum, and various Colletotrichum species, and compared it to the conventional 254 nm UV-C treatment in light and dark. We found that 222 nm far UV was several-fold more effective than 254 nm UV-C in killing conidia of these pathogens, did not require a dark period for enhancing its efficacy, and had no negative effect on plant photosynthesis, pollen germ tube growth and fruit set at doses used in our experiments. The independence from the light conditions most likely spawns from the mechanism of far UV that targets mainly proteins and not DNA as is the case with 254 nm UV-C. Using 222 nm far UV light would allow treatment application at any time of the day, as there is no longer the need for a period of darkness with 254 nm UV-C irradiation. The greater efficacy of 222 nm far UV light treatment will allow the mobile UV applicator to travel at increased speeds and cover much greater field area in a given time, making the UV technology even more useful for protecting plants from fungal pathogens.