PT  - JOURNAL ARTICLE
AU  - D. W. Williams
AU  - H. L. Andris
AU  - R. H. Beede
AU  - D. A. Luvisi
AU  - M. V. K. Norton
AU  - L. E. Williams
TI  - Validation of a Model for the Growth and Development of the Thompson Seedless Grapevine. II. Phenology
AID  - 10.5344/ajev.1985.36.4.283
DP  - 1985 Jan 01
TA  - American Journal of Enology and Viticulture
PG  - 283--289
VI  - 36
IP  - 4
4099  - http://www.ajevonline.org/content/36/4/283.short
4100  - http://www.ajevonline.org/content/36/4/283.full
SO  - Am J Enol Vitic.1985 Jan 01; 36
AB  - This study compares the prediction of phenology models for the grapevine cultivar Thompson Seedless that are based on degree days (°D above 10°C) with patterns observed in the field. Budbreak, bloom, and the development of total soluble solids were monitored in six vineyards over a latitudinal range of 300 km in the San Joaquin Valley of California in 1983. The models predicted dates of 50% budbreak and 50% bloom within a few days of the observed events. Relative calendar timing followed the expected latitudinal trends, with earliest budbreak and bloom dates observed at the southernmost sites. The model predicted maturity (20° to 21.5°Brix) reasonably at four vineyards and underestimated it at the other two, one of which had vines that were water stressed and lightly cropped relative to the others. Predictions of °Brix differed substantially from observations in the range 14° to 18° at most sites. The factors influencing vine phenology, including temperature, solar radiation, water availability, and vine management practices, are discussed.