BFH, Bern, Switzerland

Application of UV-B Light for the Control of Powdery Mildew in Greenhouse Cucumber Production
‍Articlerelated to the Master’s thesis by André Wêndabo KientegaSubmitted to Dr. Fabio MascherZollikofen, October 30, 2025.

Abstract
Powdery mildew, primarily caused by Podosphaera xanthii, is a major constraint in cucumber (Cucumis sativus L.) production in greenhouse
, potentially leading to yield losses of up to 50%. Conventional control methods rely on the use of sulfur and synthetic fungicides such as
, raising concerns regarding environmental contamination, health risks, and the
development of resistance.

This study evaluated a prototype light-emitting diode (LED) emitting ultraviolet B (UV-B) at 310 nm as a sustainable alternative for disease control, through direct inactivation of the pathogen and induction of plant defenses. Two phytotron trials, one trial in an experimental greenhouse
, and one trial in a commercial greenhouse were conducted to evaluate the device’s efficacy as well as the risks of phytotoxicity.
‍
Under controlled conditions, a UV-B dose of (confidential) mJ·cm⁻² caused no symptoms of phytotoxicity, thereby validating this dose for subsequent greenhouse trials. In the experimental greenhouse, UV-B irradiation alone reduced the disease with an efficacy equivalent to conventional sulfur applications (84.6%), while an integrated strategy combining UV-B and a 50% reduction in sulfur maintained full plant protection.
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In the commercial greenhouse, disease pressure could not be quantified due to the absence of inoculation and low natural disease pressure. Fruits treated with UV-B showed no differences compared to controls in terms of their antimicrobial properties and their ability to heal after cutting.

These results confirm that UV-B technology can contribute to crop protection without negatively impacting the postharvest quality of fruits, thereby supporting its integration into sustainable disease management programs in protected cucumber cultivation.