Root diseases of damping off and Fusarium wilt are the most serious problems in the summer cultivation of spinach (Spinacia oleracea L.) in a greenhouse. The incidence of root diseases was suppressed to one third in the greenhouse with ultraviolet absorbing vinyl film (UVA) as compared with that in the common agricultural vinyl film (CA) greenhouse. Suppression of the disease by UVA was evident in the summer cultivation at high temperatures from June through September. The fungi isolated from the diseased roots of spinach were mainly Pythium spp., Fusarium spp. and Rhizoctonia spp. Isolation frequency of Pythium spp. was the highest, followed by Fusarium spp., and the occurrence of Rhizoctonia spp. was sporadic. Among these fungi responsible for damping off of spinach, Fusarium spp. were suppressed the most in the UVA greenhouse.
Key words: Spinach; disease control; ultraviolet-absorbing vinyl film.