Ambient UV manipulation in greenhouses: plant responses and insect pest management in cucumber

Effects of different polyethylene covers with different light transmission properties on growth and productivity of two commercial cultivars of cucumber (Cucumis sativus L.) namely 'Safa 62' and 'Aseel' were studied under protected cropping systems. Cladding treatments included plastic covers of UV transparent (UVT), UV opaque (UVO), standard clear as well as the Egyptian local clear film. Results showed that, for the two studied cultivars, plants grown under the presence of UVB&A radiation (UVT cover) resulted in significant decrease in their vegetative characters (leaf area, plant height, and leaf dry weight) when compared with plants grown under either the absence of UVB&A radiation (UVO cover) or standard cover. Plants grown under UVO cover showed a significant increase in their vegetative characters when compared with plants grown under other films. No significant differences were found between UVT and UVO covers in total fruit yield per plant even with the pronounced differences in their vegetative responses to both films. However, both films exhibited a higher yield in comparison with standard and local films especially with cultivar 'Aseel'. Significant differences were found between examined covers on aphid's infestation. Plants grown under UVO cover had a minimum infestation throughout the experiments in the two seasons for both cultivars. Interestingly, UV radiation reduced aphid population but with lower influence than UV-blocking film.