For the 1997 season, several changes in the specific objectives of this project were implemented at the request of cooperators with Fetzer Vineyards. The modifications reflect an interest in generating research-based information which would be readily applicable to grape growers whose vineyard practices include a broad array of activities (i.e., from essentially organic to more conventional practices). Beginning with the 1997 season, the Optimal Viticulture Systems project included/the following three studies: 1) management of berm vegetation, 2) alternative control of powdery mildew, and 3) interrelationship of factors involved in mite pest problems. Unfortunately, since the decision to modify the project was not finalized until late in the spring, it was not possible to implement the berm management and powdery mildew components of the project during 1997. The third study in the Optimal Viticulture project focuses on a multifactored analysis of vineyard parameters associated with high density mite areas as compared with factors found in relatively mite-free areas in a given vineyard. Two vineyards (Chardonnay and Zinfandel) were selected for collection of data on mite population levels, site characteristics, vine water relations, and vine productivity. Both vineyards have demonstrated a history of mite problems occurring in various areas. These locations were designated as hot (mite pressure) and cold (no mite pressure) sites. Early in the season, a total of 18 locations in the Chardonnay vineyard and nine locations in the Zinfandel vineyard were surveyed to identify appropriate plots for the mite/vine stress study. In the Chardonnay vineyard, there appeared to be an inverse pattern of mites being heavier on foliage of hot site vines, while Erythroneura leafhopper nymphs were more abundant on foliage of cold site vines. Data from the Zinfandel vineyard revealed no consistent patterns of numerical differences for either mites or leafhoppers. The Chardonnay vineyard had statistically significant differences in yield and grapevine water relations for the 1997 season. Yields were highest for the cold sites. This can be attributed to both higher cluster weights and an increased number of berries per cluster. However, the treatments had no significant effect on fruit composition. Grapevine water relations were significantly affected by level of mite pressure in 1997. Cold sites had higher stomatal conductance and transpiration in the Chardonnay vineyard. On the other hand, the Zinfandel vineyard showed no statistically significant differences for yield, fruit composition and grapevine water relations. In conclusion, significant differences in viticultural performance were noted between hot and cold sites in the Chardonnay vineyard. Numeric differences were observed for mite populations but the differences were not statistically significant. A greater level of replication may have resulted in more clear cut results. To this end, in 1998, the focus of the study will shift to the Chardonnay vineyard and additional data collection sites have been added. Further research is needed to determine the factors involved in the observed differences.
/wp-content/uploads/2017/09/AFV-Header-Logo.png 0 0 AVF /wp-content/uploads/2017/09/AFV-Header-Logo.png AVF1997-10-18 14:16:072017-10-18 14:16:52Optimal Viticulture Systems Comparison