1. Use of Gibberellic Acid for Management of Bunch Rot on Chardonnay and Vignoles Grape.
- Author
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Hed, Bryan, Erie, Lake, Ngugi, Henry K., and Travis, James W.
- Subjects
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EFFECT of gibberellic acid on plants , *GRAPE diseases & pests , *GRAPE varieties , *BOTRYTIS cinerea , *VINEYARDS , *AGRICULTURAL productivity , *REGRESSION analysis - Abstract
Harvest bunch rot of wine grape, caused primarily by Botrytis cinerea, is a perennial problem limiting the productivity of eastern vineyards, especially on cultivars with compact clusters. The aim of the present study was to evatuate the effectiveness of gibberellic acid (GA) sprays at reducing the compactness of Chardonnay and Vignoles clusters and minimizing bunch rot. Applications of GA reduced the number of berries per centimeter and the incidence and severity of bunch rots in Vignoles and, to a lesser extent, in Chardonnay over three consecutive years; however, the magnitude of GA effects often depended on the timing and rate of application. Bloom GA applications were more effective (P < 0.001) at reducing compactness and bunch rots than prebloom applications. Significantly, negative effects of GA applications on yield were negligible based on data from 4 years of trials on single vines and 2 years of data on 24-vine plots of Vignoles, provided the rates did not exceed 25 ppm. Regression analysis showed that berries per centimeter accounted for between 89 and 94% of variation in the incidence of Botrytis rot on Vignoles. On Chardonnay, compactness accounted for 53% of the variation in incidence, and the estimated compactness level at which no bunch rot would occur was 4.40 ± I .05 (mean ± standard error) berries per centimeter. The relationship between cluster compactness and spray coverage of berries was also investigated in two separate experiments. Spray coverage of individual berries decreased linearly as cluster compactness increased within the range tested (3 to 18 berries per centimeter). Cluster compactness accounted for two-thirds of the variation in individual berry coverage, and coverage was reduced by 40 to 50% for clusters with about 1 8 berries per centimeter. These results strongly support the use of GA in integrated management of bunch rot on Vignoles and Chardonnay in eastern U.S. vineyards. [ABSTRACT FROM AUTHOR] more...
- Published
- 2011
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