Date: June 30, 2020

Project Title: Influence of climate variability on grapevine phenology

Project Duration: 3 Years

Principal Investigator(s): Melba Salazar
Organization: Washington State University
Address: 24106 N. Bunn Rd, Prosser
Telephone: 509-786-9201

CO-PI: Markus Keller
Organization: WSU, IAREC-PROSSER
Telephone: 509-786-9263

Cooperator(s): Boushey Vineyards
Description of Participation: advice, access to the vineyards for data collection

Cooperator(s): Hogue Ranches
Description of Participation: advice, historical data, access to the vineyards for data collection

Project Summary:

There is an urgent need to identify Washington wine grape temperature thresholds from woolly buds through the first leaf. This information will be very valuable for climate variability, risk assessment, and frost control during the most sensitive periods. Knowledge of the critical temperatures and frost sensitivity of non-dormant tissue of grapevine cultivars for each of the development stages that reflect the decrease in hardiness level during budbreak and posterior development in spring can aid in vineyard design by helping growers to determine the most susceptible cultivars in the best sites. It will help guide appropriate crop management decisions especially for activating frost protection systems during the spring which should be started sooner on the more susceptible cultivars.

Phenological observations have been collected in a commercial vineyard and Roza (IAREC experimental plots) for Cabernet and Chardonnay and data was collected during four growing seasons. The duration of these stages was established in terms of thermal time (GDD), using the accumulation of the average daily temperature above the base temperature Tb, and estimated temperature thresholds. A simple thermal-time (TT) model based on historical observations of phenological stages for local conditions was developed using different thresholds. Based on this evaluation, the heat unit requirements for the beginning of the season, bloom, and veraison can be determined.

For critical temperature determination of non-dormant reproductive tissue, we have developed an automated freezing sampler from previous cold hardiness studies to perform controlled freezing tests on non-dormant reproductive tissue from samples collected in local vineyards at and around the Irrigated Agriculture Research and Extension Center (IAREC).

The goal was to develop an information delivery system and media tool in collaboration with stakeholders and the industry at large, to present the observed data on the web as a Decision Aid Tool. A preliminary web site was developed for grapevine phenology with information from previous projects.

Provide a guide (decision aid tool) for appropriate crop management, and especially for activating frost protection systems during the spring, which should be started sooner on the more susceptible cultivars. In addition, an early prediction of budbreak would be useful to assess the risk of spring frost damage and the potential for its mitigation for site-variety combinations.

Although degree-day accumulations have been related to the progression of phenological stages, no information is available on a variety of specific heat unit summations using different combinations of base temperatures and upper-temperature limits to predict those stages under WA conditions.

Read more by downloading the full report above.

Climate // Viticulture //