ELSEVIER C’r,,,’ ,‘,i,,n ,,o,, Vcrl. I% No 7. pp. hi-642. IV97 t, 1047 Puhlkhcd hv Ekvicr Science Lkl PII: SO261-2194(97)00046-X Dl Effect of filtration of solar light on the production of conidia by field isolates of Botrytis cinerea and on several diseases of greenhouse-grown vegetables Y. Elad 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 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQP 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 transmissi- bility 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 35-7596. Diseases caused by Sclerotinia sclerotiorum on cucumber, Fulviu fulva on tomato and cucumber powdery mildew also were reduced. The green film could be incorporated in disease management. 0 1997 Published by Elsevier Science Ltd Keywords: conidia; spores; conidiation; greenhouse environment; Fulvia fulva syn. Cladosporium f&urn; IPM; integrated disease management: irradiation; Pseudoperonospora cubensis; Spaero- theta fusca (fuliginea); ultraviolet; far-red; wavelength Greenhouse crops are threatened by the pathogenic flingus Botrylis cinerea Pers.: Fr. The pathogen produces conidia prolifically on rotted plant organs (Epton and Richmond, 1980). The conidia of B. cinerea are released when the vapour pressure deficit changes from a low to a high (Epton and Richmond, 1980). Conidia that settle on plant surfaces in green- houses germinate when water persists on the suscep- tible organs for several hours at favourable temperatures (Yunis and Elad, 1993; Yunis et al., 1994). Sporulation of B. cinerea colonies is affected by light and several related studies have been carried out (Hite, 1973b; Hyre, 1972; Suzuki et al., 1977; Tan, 1974a, b, 1975a, b, 1978; Tan and Epton, 1973, 1974). Various range of wavelengths either promote or inhibit sporulation of B. cinerea. Near-ultraviolet (UV) (300-400 nm) and far-red ( > 720 nm) light induce sporulation, whereas blue (380-530 nm) light inhibits it. Far-red also induces sporulation that is inhibited by blue light. Red (620-720 nm) light inhibits sporulation induced in cultures by far red but does not affect sporulation in cultures exposed to near-UV with or without a subsequent exposure to far red (Epton and Richmond, 1980). Hite (1973a) postulated that control of light wavelengths in the greenhouse could reduce the build-up of inoculum of B. cinereu and thereby reduce grey mould epidemics. Polyvinyl chloride film reduced incidence of grey mould in greenhouse- grown cucumbers because of its property of screening out light of wavelengths shorter than 390 nm (Honda et al., 1977). Sasaki et al. (1985) found that UV-absorbing vinyl films reduced sporulation and infection caused by B. cinereu and indicated that light in the 300 to 340 nm wavelength range induced sporulation of B. cinereu. This range is probably more precise compared with the 300-400 nm given by Tan and Epton (1973) for induction of sporulation in B. cinereu. Light quality also affects sporulation in Botrytis squamosu (Bergquist et ul., 1972) and B. fubae (Harrison and Heilbronn, 1988). The effects of light on the sporulation of fungi are not restricted to Botrytis spp. The phenomenon was documented by Colhoun (1973) and Leach (1971) and has been studied under experimental conditions for fungi such as Altemuriu, Cercosporellu, Fusurium, Py riculuriu, Trichoderma, Helminthosporium, Stemphy - lium and Verticillium (Aragaki, 1962; Honda and Nemoto, 1985; Honda and Sakamoto. 1968; Kumagai Crop Protection 1997 Volume 16 Number 7 635