Predicting the Date of Bud Burst in Grapevines

Abstract

It was possible to forecast the date of bud burst under South African winter temperatures (Region III) using the Pouget-formulae and principles, and to establish a scale of bud burst for cultivars grown in South Africa. The sum of daily temperature effects was higher under the warmer South African conditions which resulted in changes in the formulae for determining the daily effect of temperature and the cultivar coefficient on the bud burst date. Highly significant linear relationships were, however, obtained and it was possible to predict the date of bud burst fairly accurately.Predicting the date of bud burst of grapevines has a number of practical advantages in that, inter alia, pruning can be planned more efficiently (e.g. the best time for pruning is 2-3 weeks before bud burst), while treatments against diseases (e.g. bud mite) and to homogenise and increase the percentage of bud burst (hydrogen cyanamide) can be timed more accurate! y.From bud burst dates obtained over 25 years for 22 cultivars in France (Bordeaux, Region II according to Winkler et al., 1974) as well as minimum and maximum temperatures during the period prior to bud burst, Pouget (1988) established a time scale for bud burst. Moreover, he indicated that it was possible to calculate the potential date of bud burst 2-3 weeks in advance. These calculations were based on "the law of the effect of temperature on rate of bud burst" (Pouget, 1967) and the sum of daily minimum and maximum temperature values from a fixed date during ecodormancy (post-dormancy).The aim of this investigation was to determine the possibility of using Pou get' s formulae and cul ti var coefficients to predict the date of bud burst of cultivars grown in South Africa under conditions of higher winter temperatures. This would then also make it possible to determine similar cultivar coefficients for cultivars commonly grown in South Africa. MATERIALS AND METHODSBud burst dates were recorded over 8 years on 15 Vitis vinifera L. cultivars grown on the YORI experimental farm, Stellenbosch (Region III). Dates used in this study were recorded when 50% of the buds allocated during pruning (spur pruned and long bearers) showed green colouring. The cultivars were grafted onto 99 Richter (cl RY 30) with a planting width of 3,0 x l,5m, trellised on a l,5m slanting trellis and pruned during August. Cultivars of which coefficients were determined by Pouget (1988), viz. Gewtirztraminer, Chasselas blanc (Chasselas dare), Shiraz, Sauvignon blanc and Ugni blanc were used as reference cultivars.Duration to bud burst: The duration to bud burst (D) was initially calculated as the number of days from 1 June, 15 June, 1 July and 15 July (during ecodormancy) up to and including the date of bud burst. These dates are sufficiently distant from bud burst for the buds of the various cultivars to be considered as being in a very similar physiological state regardless of date of bud burst.Sum of daily temperature effects: According to Pouget (1988) temperature has a specific action on a cultivar...

Heat Unit Requirements of “Flame Seedless” Table Grape: A Tool to Predict Its Harvest Period in Protected Cultivation

“…Given this inconsistency, and according to the strong preference shown by Arnold [20] and Perry et al [21] for the method based on the least CV in GDD, we checked the T b value that presented the least CV in the estimations of GDD between bud break and ripening in the range of temperature of 3-12 • C, proposed as likely T b by different authors [22][23][24][25]. Figure 1a shows how the CV of GDD estimations diminishes very slightly as the temperature falls between 10 and 5 • C. On the contrary, the CV of GDD rose considerably beyond these limits.…”

Comparison of methods for determining budburst date in grapevine

“…Based on the knowledge of grapevine chilling and forcing temperature requirements for endodormancy and ecodormancy release, several attempts have been made to develop agro-meteorological models for budburst timing prediction (Pouget 1988;Williams et al, 1985;Swanepoel et al, 1990;Bindi et al, 1997;Parker et al, 2020 and references herein). The common growing degree days (GDD) models simulate grapevine budburst after a specific sum of forcing temperatures, which are accumulated generally after 1 January for the northern hemisphere (i.e., when endodormancy is assumed to be already broken) (McIntyre et al, 1982;García de Cortázar-Atauri et al, 2009).…”