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), we re compared with conventional nets of the same mesh size for their protecti ve capacity against vegetable insect pests and the spread of virus. Convent ional and bionet screens with densities of 16- and 30-mesh were not effecti ve in preventing the penetration of Bemisia argentifolii Bellows & Perring and Aphis gossypii Glover into walk-in tunnels covered pith these nets. How ever, 50-mesh bionet screens significantly reduced the penetration of white flies into tunnels as well as the spread of tomato yellow leaf curl virus ( TYLCV). Fifty days after planting, 30% disease incidence was recorded in un sprayed tomatoes Lycopersicon egculentum grown under 50-mesh bionet screens compared with 80% incidence in tunnels covered with conventional 50-mesh n et. Fifty-mesh bionet screens were significantly more effective than the co nventional screens of the same mesh size in protecting tomato against leafm iners (Liriomyza trifolii Burgess) and red mites (Tetranychus telarius L.) as well as in protecting cucumbers (Cucumis sativus) against A. gossypii. N one of the tested bionet screens was superior to the conventional screens a gainst the western flower thrips, Frankliniella occidentalis Pergande. The size of thrips populations under the different screens was similar and unaf fected by either the mechanical or optical properties of the net. The use o f insect-proof bionet screens as a tool of integrated pest management in ve getable crops is discussed.