2019/2020 Nova Scotia Wine Grape Bud Hardiness Report no. 8: February 17 – 18

A wine grape bud hardiness report is generated and distributed to the Grape Growers of Nova Scotia (GGANS) membership on a bi-weekly basis throughout the dormant season. The bi-weekly survey is performed on 3 vinifera cultivars (‘Chardonnay’, ‘Riesling’, ‘Pinot Noir’) and 2 hybrid cultivars (‘L’Acadie Blanc’, ‘Marquette’) and involves 10 grower collaborators for a total of 23 varietal blocks in total. Each report uses a table to show the latest low temperature exotherm (LTE) levels for the present and past weeks. The report also includes comments highlighting observations over the last reporting period, a plot showing the change in LTE values throughout the season, the historical 100 year minimum values and the present year’s minimum values. Three times throughout the season (early, middle, late) 11 “extra” varieties (‘Baco Noir’, ‘Chenin Blanc’, ‘Geisenheim’, ‘Leon Millot’, ‘Lucie Kuhlman’, ‘New York Muscat’, ‘Pinot Gris’, ‘Sauvignon Blanc’, ‘Seyval Blanc’, ‘Seyval Blanc’, ‘Vidal Blanc’, ‘Ortega’) from 22 additional varietal blocks are also reported. On February 15th, temperatures dropped below -20 °C in many areas of the Annapolis Valley. At the southwest end of the Valley, the minimum temperature was -13.9 °C while the Kentville and Wolfville area saw temperatures in the -20 to -22 °C range. There were also some locations where temperatures were below -23 °C, but we do not have enough data to estimate the extent of these extreme temperatures. Figure 1 shows that the LTE50 bud-hardiness estimates were very close to the observed low temperature and Table 1 shows that the LTE10 values for vinifera varieties were above the observed low temperature. Because of this we estimate lethal bud damage, in vinifera varieties, of between 10% and 50% in locations where temperatures were below -20 °C. In addition to bud-hardiness we are also monitoring dormant bud viability in many of our sites and will report our results as soon as the data is processed. Both the figure and table show a very slight de-acclimation in all varieties compared to the previous survey date. We will be watching closely to see if this trend continues in the coming weeks.