BFH, BERN SWITZERLAND

Use of UV-B light to control powdery mildew of cucumber in greenhouse production

Article based on the Master’s thesis by André Wêndabo Kientega. Submitted to Dr Fabio Mascher. Zollikofen, 30 October 2025.

Abstract

Powdery mildew, mainly caused by Podosphaera xanthii, is a major constraint in greenhouse cucumber (Cucumis sativus L.) production and can lead to yield losses of up to 50%. Conventional control methods rely on sulphur and synthetic fungicides, which raises concerns about 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 defences. Two phytotron trials, one trial in an experimental greenhouse and one in a commercial greenhouse were carried out to assess the efficacy of the device and the risk of phytotoxicity.

Under controlled conditions, a UV-B dose of (confidential) mJ·cm⁻² caused no symptoms of phytotoxicity, validating this dose for the subsequent greenhouse trials. In the experimental greenhouse, UV-B irradiation alone reduced the disease with an efficacy equivalent to conventional sulphur applications (84.6%), while an integrated strategy combining UV-B with a 50% reduction in sulphur maintained complete plant protection.

In the commercial greenhouse, disease pressure could not be quantified owing to the absence of inoculation and low natural disease pressure. UV-B-treated fruit showed no differences from the controls in terms of antimicrobial properties and wound-healing capacity after cutting.

These results confirm that UV-B technology can contribute to crop protection without any negative impact on the post-harvest quality of the fruit, supporting its integration into sustainable disease management programmes for protected cucumber cultivation.