Abstract

The effect of temperature and petal wetness on the infection of Botrytis cinerea in rose flowers was studied by combining temperatures of 10, 15, 20 and 25°C with periods of petal wetness of 8, 16, 24 and 32 h. An increase in the severity of gray mold was observed when petal wetness period increased. Lower level of disease severity was verified at 10°C for all wetness periods as well as for the temperature of 25°C and wetness period of eight hours. In this wetness period, the lowest severity indexes were observed in all the temperatures tested. The maximum disease severity was observed at 20°C with 24 h of petal wetness. A model of multiple regression analysis was tested to associate temperature and wetness period. A quadratic effect of temperature was observed, which was overcome by free water time. The results show that infection on the rose flower petals depends on the period of wetness of the petals; maximum estimated severity occurred at 25°C with 32 h of petal wetness; the temperature of 10°C can reduce the severity of gray independently of the petal wetness period; at higher temperatures high disease severity is dependent on the wetness on the petals.

Key words: Disease severity, flowers, gray mold, Rosa hybrid.