Enhancing Vine Resilience and Delaying Ripening: Novel Late-Season Practices for Grape Production in Central California
Luis Ortiz, Luca Pallotti, Eve Laroche-Pinel,
William Whalen, and Luca Brillante*
*Department of Viticulture and Enology, California State
University Fresno,
2360 E Barstow Ave, Fresno, CA, 93740
(lucabrillante@csufresno.edu)
Global warming is significantly compromising grape production in regions like central California. Late-season practices aimed at reducing the efficiency of the photosynthetic apparatus might be the solution to improve vine resilience and delay ripening. In this trial, an untreated control © was compared with applications of pinolene (P) and diatomaceous earth (D). A fourth treatment involved shoot twisting (T), seeking to achieve the benefits of traditional topping by breaking xylem tissue without overexposing clusters. Leaf area, light interception, midday stem water potential, and gas exchange were measured over the 2023 season. Berry ripening was followed and grape production at harvest was evaluated. Twisting determined the desiccation of the upper portion of the shoot, reducing leaf surface while maintaining a low level of irradiance in the fruiting zone. Stem water potential results showed that D, and especially T, partly alleviated stress conditions, while P led to a worsened vine water status. D had the most pronounced effect on gas exchange, especially transpiration and stomatal conductance, thereby leading to higher water use efficiency trend in the treated vines. D and T fruit exhibited greater berry weights during the first half of the season, likely due to the improved water status, while P berries had reduced weight. All applied treatments significantly affected berry ripening, resulting in increased titratable acidity and lower must pH, without compromising crop yield at harvest.
This trial highlights that innovating traditional, easily mechanizable practices such as topping, and introducing new products like diatomaceous earth can be effective techniques to mitigate summer heat stress and delay berry ripening, particularly in hot, dry regions such as CA’s Central Valley.
Funding Support: N/A
