Grape harvesting periods based on degree-days in Paraná state, Brazil

Abstract

Grape harvesting period can be decisive for greater profitability to vine growers and for production quality. Thus, the objective of this work was to evaluate grape harvesting periods based on degree-days (DD) during different pruning periods, and under the risk of frosts in the State of Paraná. Based on a series of maximum and minimum temperatures data from 21 conventional stations managed by IAPAR, from 1976 to 2010, this study evaluated the risk of frosts and the degree-days required to complete each cycle in several regions of the state. Results showed that the occurrence of frosts is a restrictive factor for vine crops pruning in regions with higher altitudes and latitudes. For cultivars with low degree-days needs, results showed that in the Northeast of the state harvest could occur from the second ten-day-period of September, with winter pruning by July 5, making the commercialization during periods of less grapes offer. In this same region, cultivars with more needs of degree-days could be harvested between the first and second ten-day period of November. For the Central, Southern and Eastern regions, the risk of frosts in the month of July is high and pruning may result in cold damages to new shoots and vines. Therefore, harvesting must occur from January to May in these regions.