Evaluation of new greenhouse covers with modified light regime to control cotton aphid and cucumber (Cucumis sativus L.) productivity

Cucumber (Cucumis sativus L.) is infested by cotton aphid (Aphis gossypii Glover) which occurs mainly on the growing tips of vines, sucking nutrients from the plant resulting in distortion, leaf curling, and yield loss. Horticultural plastic films with modified light regimes were selected to control aphid in the greenhouses for the production of cucumber. The covers have specific UV radiation diffusion properties. Two cucumber cultivars (Aseel and Safa 62) were planted during two spring seasons (2014 and 2015) with two new cladding materials (UV transmitting cover (UVT) and UV opaque cover (UVO)) compared to Egyptian (Local) and British (STD) materials as controls. Cotton aphid infestations were examined weekly during both seasons. There were no significant differences in relative humidity and light intensity throughout both seasons between the new design and the control cover materials. In contrast, there were significant differences in temperature for all three months and the UVO had the lowest air temperature compared to other cover types during both seasons. At the beginning of experiments, the numbers of aphids on leaves in UVT and UVO were significantly lower than the controls. Chemical analyses of cucumber leaves associated with manipulation of UV showed that total phenolics levels were lower under new materials compared to the control. Chlorophyll and phosphorus content were significantly lower the Aseel compared to the Safa 62 cultivar. At the end of experiments, the type of cover had a significant effect on the number of fruits/m2, early yield/m2 and total yield/m2 for both seasons and the UVO and UVT were superior in this respect for the Safa 62 cultivar. Compared to Local, the total yield/m2 of the Safa 62 cultivar was found to be increased by 13%, 21%, and 25% for STD, UVT and UVO covers, respectively. These results suggest that the new greenhouses plastic covering materials can be used safely in semi-arid climates and have a great influence on the productivity of both cucumber cultivars via controlling UV radiation and aphid infestation.