Inibição do míldio e características físico-químicas do mosto e vinho submetidos à aplicação pré-colheita de fosfito de potássio em videira 'cabernet sauvignon'

Abstract

This study aimed to evaluate the efficacy of potassium phosphite on the of mildew control in a commercial vineyard of Cabernet Sauvignon, Italian clone R5 on SO4 rootstock, also evaluated the influence of this product on the physico-chemical characteristics of the must and wine. The study was conducted by the Núcleo de Estudo, Pesquisa e Extensão em Enologia (NEPE²) of Universidade Federal do Pampa – Campus Dom Pedrito in a commercial vineyard in the municipality of Dom Pedrito - Rio Grande do Sul, Brazil. The experimental design was a randomized block design with four repetitions for each treatment, each repetition consisted of five plants. The treatments on the vines were: T1 – Control (no application of phosphite), T2 - Reforce® (1,5L.ha-1) or 200 m.L-1 for 100 L-1 of water; T3 – Yantra® (1,5L.ha-1) or 200 m.L-1 for 100 L-1 of water, and T4 – Fortaleza® (1,5L.ha-1) or 200 m.L-1 for 100 L-1 of water. Treatments were applied four times during the vegetative growth of the vines. Periodicamente, foram feitas análises visuais para constatação da presença de sintomas de míldio nas folhas ao longo do experimento. Visual analyses were periodically held to watch for mildew symptoms in the leaves throughout the experiment. Three analyses of wine were held, including two before harvest and another on the day of winemaking. After harvesting, the wine was made by classical method of winemaking in red grapes with the grapes of each treatment. It was evaluated: total soluble solids - TSS (Brix) pH, total acidity and potassium of the must. In wine, the variables analyzed were: ethanol, pH, total acidity, folling index and color index. The physicochemical analyzes were performed by spectrometry of Fourier transform infrared (FTIR) WineScan SO2®. Data for the variables were subjected to analysis of variance (ANOVA) and the means comparison test of Tukey, with 5.0% of probability, using free software Assistat 7.7. It was noticed statistically significant difference only in relation to TSS (°Brix), for T1 showed higher concentrations of this compound. No incidence of mildew was observed in any treatment, probably this result is due to the factor that vines are from a commercial vineyard with good pest management. For this reason, it was not possible to observe the effectiveness of commercial products in the control of mildew. We observed statistically significant differences in relation to the total soluble solids (° Brix), however, it was on T1, that there was a higher concentration of these compounds. It was noted then that potassium phosphite used in the work did not affect the physicochemical characteristics of the must and that there were no significant differences between treatments in relation to all response variables analyzed in the wine.