Elad, Y., Dept. of Plant Pathology, ARO, The Volcani Center, Bet Dagan 50250, Israel

New custom-made polyethylene films with light blockers in the far-red region of the spectrum were tested for their effect on sporulation of Botrytis cinerea. A pink-pigmented polyethylene sheet partially screened visible light mainly from 470-650 nm, with lowest transmissibility at 500-580 nm, and a green-pigmented sheet partially screened it mainly from of 560-800 nm, with lowest transmissibility at 600-700 nm. Both films screened ultraviolet radiation up to 380 nm. Light filtration inhibited sporulation of B. cinerea cultures on artificial medium, tomato leaves, and cucumber fruits. However, the extent of inhibition varied with fungal isolate, the quality of the light that reached the culture and the medium that supported the fungal colonies. Some isolates sporulated in darkness, so an indirect effect on the host plant has been important in reducing the disease suppression. The green-pigmented polyethylene reduced conidial load and grey mould in commercial greenhouses by 35-75%. Diseases caused by Sclerotinia sclerotiorum on cucumber, Fulvia fulva on tomato and cucumber powdery mildew also were reduced. The green film could be incorporated in disease management.