Influence of the Use of Double Roof with Increased Ventilation on the Development of Fungal Diseases in a Mediterranean Greenhouse

Mediterranean greenhouses commonly rely on passive climate control techniques to reduce dependence on energy-intensive systems. This study was conducted in Almería (Spain) in a multi-span greenhouse divided into two sectors: a West sector equipped with a double-roof system using a pink sunlight spectrum photoconverter film combined with an increased natural ventilation surface, and an East control sector with standard ventilation and a calcium carbonate-whitened roof. The effects of this integrated passive climate management configuration on the development of naturally occurring fungal diseases were evaluated in tomato (Solanum lycopersicum L.), pepper (Capsicum annuum L.), and cucumber (Cucumis sativus L.). Powdery mildew (Leveillula taurica) and early blight (Alternaria linariae) were observed in tomato; powdery mildew in pepper; and downy mildew (Pseudoperonospora cubensis), powdery mildew (Podosphaera xanthii), and gummy stem blight (Stagonosporopsis spp.) in cucumber. Across crop cycles, the sector combining double roofing and enhanced ventilation consistently exhibited lower disease severity for powdery mildew, downy mildew, and gummy stem blight compared with the control sector. In contrast, early blight did not show a clear or consistent response to the greenhouse configuration. Overall, the results indicate that the combined use of a double-roof system with a sunlight spectrum photoconverter film and increased natural ventilation can contribute to improved microclimate regulation and reduced fungal disease pressure under Mediterranean greenhouse conditions. This integrated passive approach may therefore represent a useful complementary component of sustainable disease management strategies in protected horticulture.