Influence of Vine Trellis Training Systems on Eutypa Lata in a Cabernet

During the 1998 season the emphasis of this project shifted from intensive viticultural data collection to an investigation of the impact of training system on incidence and severity of Eutypa infection and management of vines infected with Eutypa. Baseline viticultural data (to maintain treatments and monitor the impact of Eutypa incidence) consisting of yield, fruit composition and vegetative growth assessment were collected. This season produced significantly greater yields for the minimally-pruned treatment than for any other treatment. The machine-pruned and hand-pruned treatments had yields that were comparable. A significantly greater number of clusters were found on minimally-pruned vines. Increased yield for minimally-pruned vines appeared to be directly related to higher cluster number. Mechanized treatments (minimal and machine pruning) significantly reduced cluster weight when compared to hand-pruned treatments. Planting vines on a low capacity soil type produced lower yield and numbers of clusters per vine. Fruit composition was significantly affected by treatment in 1998. Soluble solids data were grouped in a narrow range of values that although significantly different, would all be acceptable for the production of a medium-bodied red wine. The minimally-pruned treatment displayed a delay in maturity that has been a characteristic of this treatment during the course of the study. Vines planted in a low capacity soil type showed that they were able to produce more soluble solids and higher anthocyanin content than vines planted in the high capacity soil type. A significantly greater number of shoots per vine were observed for the minimally-pruned treatment. Measurement of mature nodes is an estimation of the capacity of a vine to grow and produce crop in a sustainable manner. There were no significant differences in mature node data so it can be said that treatments had comparable levels of growth over the length of the season. Symptoms of Eutypa infection were observed in the plot for the third consecutive season. Suspected vines were marked and later sampled for analysis with DNA-based diagnostic tools at the Molecular Marker Laboratory in the Viticulture and Enology Research Center at California State University, Fresno. The result of this analysis will be presented in a supplementary report. Minimally-pruned vines did not display symptoms of Eutypa infection. Visual ratings of Eutypa incidence were confirmed with assistance from Dr. Doug Gubler, Extension Plant Pathologist, UC. Cooperative Extension.