Ultraviolet-absorbing screens serve as optical barriers to protect crops from virus and insect pests

Plastic screens with UV absorbancy in the UV-A and UV-B range (bionets), were compared with conventional nets of the same mesh size for their protective capacity against vegetable insect pests and the spread of virus. Conventional and bionet screens with densities of 16- and 30-mesh were not effective in preventing the penetration of Bemisia argentifolii Bellows & Perring and Aphis gossypii Glover into walk-in tunnels covered pith these nets. However, 50-mesh bionet screens significantly reduced the penetration of whiteflies into tunnels as well as the spread of tomato yellow leaf curl virus (TYLCV). Fifty days after planting, 30% disease incidence was recorded in unsprayed tomatoes Lycopersicon egculentum grown under 50-mesh bionet screens compared with 80% incidence in tunnels covered with conventional 50-mesh net. Fifty-mesh bionet screens were significantly more effective than the conventional screens of the same mesh size in protecting tomato against leafminers (Liriomyza trifolii Burgess) and red mites (Tetranychus telarius L.) as well as in protecting cucumbers (Cucumis sativus) against A. gossypii. None of the tested bionet screens was superior to the conventional screens against the western flower thrips, Frankliniella occidentalis Pergande. The size of thrips populations under the different screens was similar and unaffected by either the mechanical or optical properties of the net. The use of insect-proof bionet screens as a tool of integrated pest management in vegetable crops is discussed.