Effects of Specific UV-Blocking on Plant Growth and Insect Control

Cucumber (Cucumis sativus L. 'Hiryu') and tomato (Lycopersicon esculentum L. 'Momotaro') plants were grown under four different polyolefin film greenhouses (0.15 mu m thickness) where UV wavelengths shorter than 400, 360, 350 and 340 nm, respectively, were blocked (specific UV blocking). A standard polyolefin film greenhouse was used as control. Approximately 50% of UV energy was blocked under the control greenhouse compared with that irradiating plants outside the greenhouse. Under partial UV blocking conditions, however, more than 70% of UV energy was blocked. The plant height of the seedlings did not differ among treatments, irrespective of crop. Nine different insects were captured on the adhesive films. Among these, fly, rice plant hopper, whitefly and aphid were mainly captured on yellow adhesive films, while hoverfly was mainly captured on blue adhesive films. Effects of specific UV- blocking films were the most obvious for aphid control, and the cumulative number of captured aphids decreased greatly as the rate of UV- blocking increased. Effect of specific UV- blocking plastic films was also detected on aphid infestation on the cucumber leaves. Under standard plastic film, the infestation rate increased rapidly from 24 August to 14 September, reaching 54% on 21 September, while it was significantly inhibited under specific UV- blocking conditions and the rate decreased gradually as the UV- blocking rate increased. Our results showed that specific UV-blocking plastic films are commercially acceptable for promoting Integrated Pest Management (IPM) system especially for aphid control without harming plant growth.