The study aimed to identify the periods with higher risk of frost formation and to evaluate the changes regarding the duration of the phenological cycle of the vine Cabernet Sauvignon, based on the thermal availability of Alegrete, Bagé, Quaraí, São Gabriel, Santana do Livramento and Uruguaiana, located in the Campanha region of Rio Grande do Sul state. The meteorological data such as maximum and minimum air temperature for the period from 1961 to 2010 were used. In order to determine the risk of frost formation, it was considered as favorable condition for the formation when the minimum temperature was less than or equal to 3 °C. To determine the phenological behavior of the cultivar Cabernet Sauvignon the sum of degrees-day, covering the period from August 1 to October 10 as the beginning of the sprouting. It was found that Uruguaiana and São Gabriel in early September had low frost formation risk, at 5% level, while in the other municipalities the last date occurs in early October. As for the development subperiod of Cabernet Sauvignon it is possible to observe variations in the total number of days in relation to the sprouting periods, as well as among the municipalities of Campanha.
phenology, degrees-day (DD); thermal requirement; probability; Vitis vinifera
