Fungal and bacterial diseases can severely damage vegetables cultivated in commercial greenhouses and, for integrated disease management, knowing the environmental conditions that favor the occurrence of diseases is fundamental. The objective of this work was to identify the diseases in tomato cultivated in plastic greenhouses in four locations in Rio Grande do Sul and the temperature and relative humidity favoring plant diseases. This study was done in four greenhouses, cropped to tomato, located in São Pedro do Sul, São Sepé, Ivorá, and Santa Maria (RS-Brazil), from March to October of 1998. The air temperature and the relative humidity inside the greenhouses were measured daily with a psicrometer. The diseases identified and their maximum incidence were: late blight (Phytophthora infestans): 100,0%, early blight (Alternaria solani): 98,1%, gray mold (Botrytis cinerea): 55,4%, leaf mold (Cladosporuim fulvum): 48,9%, leaf spot (Septoria lycopersici): 37,5%, soft rot (Erwinia spp.): 33,0%, fusarium wilt (Fusarium oxysporum f. sp. lycopersici): 8,4%, and watery soft rot (Sclerotinia sclerotiorum): 1,3%. Air relative humidity greater than 80%, in general, increased disease incidence, which were predominantely caused by fungi. The disease incidence on tomato varied among locations in the same climatic region due to variations in meteorological conditions and crop management practices.
modified environment; meteorological condition; fungy; crop management
