BC Grapegrowers Gather and Learn
Wine Grape Council addresses vineyard and marketing issues
The conference convened under rainy skies just a week after bloom finished at some vineyards in the northern part of the Okanagan Valley. Bloom usually finishes in the valley, British Columbia’s primary viticultural area, by the end of June.
Conference presenters covered topics as diverse as pest management, Syrah decline, labor market development for wineries and effective communication with female wine consumers.
Between talks about grapevine trunk diseases and mite control in the BC context, Dr. Stefano Poni of the Università Cattolica del Sacro Cuore in Piacenza, Italy, told growers that early leaf removal could contribute to lighter, looser clusters with minimal effects on individual berry weights.
He showed statistics from a trial in which early-season leaf removal saw berries in a control cluster reduced from 169 to 103. with resulting cluster weights of 334 grams and 207 grams, respectively. But individual berries weighed an average of 1.98 grams in the control cluster and 2.01 grams in clusters on defoliated vines. Poni pointed out that net carbon exchange per shoot relative to yield was 1.36 times greater for defoliated vines. The clusters were also looser, reducing the risk of rot; no carry-over effects on fertility were seen.
This was good news for some growers. In subsequent conversations, they said the presentation confirmed the wisdom of their practices, especially in a cool, moist season when many are anticipating successive passes to thin shoots and clusters and facilitate ripening. (Some growers during last year’s cool, extended season thinned to a single cluster per shoot. Even then, many B.C. winemakers worked with grapes registering above-par acid concentrations.)
Poni gave a second presentation later in the day that examined trellising systems. He argued for a better understanding of leaf area relative to vine yields. An efficient canopy can make use of available light, enhance ripening and even boost per-acre yields—if leaf area doesn’t exceed certain bounds. (Poni noted that trellising will be one element discussed at next year’s inaugural International Workshop on Vineyard Mechanization and Grape and Wine Quality, which he’s convening in Piacenza).
In his trellising talk, Poni advised growers that per-acre yields depend on at least eight separate variables, including on-row spacing. It’s a broad topic that goes beyond standard expectations, including common notions among growers in Europe and elsewhere and regulations for the Denominazione di Origine Controllata (DOC) designation in Italy.
“The European viticulturist typically believes that there is a negative relationship between quality and yield per hectare. Of course, this is a joke because we cannot really say if there is no crop then we get the best quality. But this is a very serious thing,” he said. “If we take examples from the literature, I could probably show you hundreds of examples demonstrating that this relationship is not true.”
Poni showed figures from a trial with Croatina vines, pointing out that a total leaf area per vine of up to 5.88 square meters could boost yields as high as 3.67 kilograms per vine—but only if the relationship between leaf area and yield is in the 1 to 1.6 square meters-to-kilogram range (soluble solids, anthocyanin and phenolics levels were on par with the control).
“We have increased yield by 20%, but you would notice that total leaf area has increased approximately by the same percentage,” Poni explained. “This leaf area-to-fruit ratio does not change, and it is perfectly understandable that they don’t get a change in quality.…I wish I had the same information in all the genotypes I grow.”
Good growing conditions for vines were not all growers were mulling. A pre-conference session on the findings of a survey of competitiveness in five wine clusters around the world—British Columbia’s Okanagan Valley as well as Extremadura, Spain; Bolgheri-Val di Cornia, Italy; Australia and Chile—was followed during the conference with a standing-room only discussion among growers and vintners.
The report highlighted the importance to individual wineries within each industry cluster of export markets and price competitiveness, and the importance of intra-cluster cooperation when engaging with specific markets.
Simon Fraser University political science professor Dr. Anil (Andy) Hira noted that supportive government policies are important in fostering clusters, but a coordinated, long-term vision is required for clusters to fulfil their potential and maximize market opportunities on behalf of member wineries. (Read about a study by Anil Hira here.