In high wire system cucumber production, powdery mildew pressure can be reduced by regular leaf thinning although high leaf contamination requires chemical treatments to maintain crop cultivation. UV-C light has been shown to prevent powdery mildew development to maintain low disease pressure in cucumber and tomato crops.
During the end of the season of a summer cultivation at French interprofessional technical center for fruits and vegetables (CTIFL), we investigated the effects of UV-C treatment to reduce powdery mildew pressure in highly infected greenhouse. Leaf contamination was scored from 0 (no spots) to 5 (more than 40% of the leaf surface covered by powdery mildew) at three plant levels. One part of the greenhouse received UV-C applications of 50 J/m² three times a week after sunset and was compared with the other part of the greenhouse (Control without UV-C treatment).
After three UV-C treatments, mildew scoring at the bottom part of the plant was significantly reduced for at least two weeks. A chemical treatment was applied in both parts of the greenhouse after the third week of the experiment as the control part of the greenhouse was severely damaged. These results show that UV-C treatments can be proposed as an alternative strategy to treat powdery mildew in highly infected greenhouse in a highwire system cucumber crop.