Organic winegrape growing, especially on the Eastern part of North America, is quite a challenging endeavor. Whether it’s fungal pathogens or pest pressure, the odds are somewhat stacked against organic growers.
In two studies published by Scientia Horticulturae, Karine Pedneault, Ph.D., a research scientist at University of Saint-Anne in Pointe-de-l’Église, Nova Scotia, Canada; and Caroline Provost, Ph.D., the director of the Mirabel Agri-Food Research Center in Mirabel, Quebec, Canada, looked at the organic vineyard as a balanced ecosystem and the benefits and limitations to fungus-resistant grape varieties.ADVERTISEMENT
We spoke with Karine Pedneault (KP) and Caroline Provost (CP) about their research and anything organic grape growers might need to know.
Q: What kind of challenges do organic winegrape growers face in terms of fungus diseases?
KP: Fungal diseases are the main diseases in grapevine. These disease do not necessarily kill the plant, but they do limit its productivity (yields). It may also damage the crop (rotten berries) and have a negative impact on wine quality.
CP: Diseases are the major challenge in organic viticulture mainly because few products are available to reduce their occurrence. Growers have few products and often have to use copper repeatedly, which can lead to other problems such as soil build-up. In addition, the small amount of registered products makes it difficult to alternate products to reduce disease resistance to fungicides. It is therefore necessary for the grower to use a combination of methods to reduce the
occurrence of diseases, for example, to perform an efficient lifting and leaf removal of the cluster zone that allows aeration of the clusters.
Q: In your studies of fungal-resistant varieties, how do these varieties improve disease management strategies for organic growers?
KP: Fungus-resistant grape varieties carry different genes that improve their resistance to fungal infections. Although they are not totally immune, they have a much better resistance to these diseases than traditional varieties (primarily Vitis vinifera varieties).
CP: Fungal-resistant varieties carry some resistance genes that reduce occurrences of diseases mainly on foliage and clusters. Moreover, other varieties have also physical proprieties that reduce their susceptibility to diseases, for example, a looser bunch or thicker skin, reducing the appropriate conditions for the development of fruit diseases. These varieties are not ‘disease resistant’ but more disease tolerant. Use of fungal-resistant varieties reduce use of fungicides during growing season and reduce costs for diseases management (e.g. leaf removal, weed control). Like organic growers have few products to control diseases, these varieties facilitate production under a organic production.
Q: Do organic growers have to make any other changes to vine management with these varieties?
KP: Somewhat. In fact, fungus-resistant varieties are generally more vigorous than Vitis vinifera varieties. Also, there is a need to fine-tune viticultural practices for these varieties, a work that has been partly achieved through years in other varieties.
CP: Best management practices for each variety need to be evaluated in order to optimize grape production in quantity but also in quality. Actually, these varieties do not require special management practices, just optimize them according to region, and mainly related to climate and soil conditions.
Q: How different are these fungal-resistant varieties?
KP: They are different in many aspects, but, in a way, they are as different as, say, ‘Cabernet Franc’ and ‘Sauvignon Blanc’ — both are Vitis vinifera varieties, but both need specific practices in the vineyard and in the winery. This is similar for fungus-resistant varieties: Most varieties are different from each other and we need to characterize those differences in order to optimize their use for grape production and winemaking.
Q: Do you foresee any limitations on the organic grower’s part to adoption of these varieties?
KP: One of the main limitations is a combination of industry and consumer. Indeed, as consumers, we like the wines from specific varieties (that is mostly true in the New World, a little less in the Old World as most popular wines are made from blends). So, we need to trace a path for those varieties to reach the consumer. On the other side, the industry is influenced by consumers so they may wait for the consumer to be ready to adopt these varieties.
CP: I think that the main limitation is the adoption of a new variety that consumers do not know, a wine that has different characteristics. The consumer also needs to be open to discoveries and try other products. If we talk about the North East American conditions, a game of different products is offered to consumers with hybrid varieties, so these consumers would probably be easier to conquer than some other regions where specific old grape varieties are well anchored.
Q: How does your research on fungal-resistant varieties tie into your research on organic vineyards as a balanced ecosystem?
KP: Actually, we wrote both papers at the same time, when we figured out that there was too much to say. The point is that variety selection (with everything that it implies) is a key to successful organic viticulture as it limits the propension to diseases at the source and thus limits the need for pesticides, which further protects the vineyard ecosystem.
CP: Grape varieties is a major concern for organic grower because this is a crucial factor to plan their vineyard management. Use of fungal-resistant varieties allow to manage vineyard with lower fungicides, lower vine management practices and result in a better yield.
Q: How do organic growers maintain a thriving ecosystem in their vineyards? What type of management strategies have to change?
CP: The scientific article details several methods that can be used in organic vineyard but also under conventional production. I will not go over all the methods described. What I can add is that it is very important to have a balanced ecosystem, mainly under organic production, because each aspect can influence another. The soil ecosystem is very complex, and it is crucial to take it into account in the vineyard management. Each practice has repercussions on the others, that’s why we have to treat them as a whole. For example, the management of ground cover (whether it is a cover crop or weed management) will necessarily have an impact on disease management as well as insect pests. Another example, foliage management, such as leaf removal of the cluster area, can reduce the incidence of disease but will also affect the ripening of the grapes. So as in any agricultural ecosystem, all elements of the environment and practices must be analyzed together. Finally, I think that the majority of organic grower has already these considerations about the balanced ecosystem, them they generally don’t have major change to do.
Q: How does organic winegrape production influence the quality of organic wine?
KP: Well, it depends to which point the concept of “organic wine” (or, say, “natural wine”) is pushed. Indeed, organic winegrape production is a system that benefits the establishment of a rich microbiota that can further contribute in winemaking, if no sulfur and no commercial yeast is used. Such practice will impact wine quality significantly because all microorganisms do not produce aromas in a similar way.
Such practices may also result in off-flavors, which of course will affect wine quality. But winemakers can grow organic grapes and still have standard winemaking practices (e.g., using sulfur and commercial yeasts for instance), as many of them are accepted in organic winemaking.
Q: Is there any part of your research that you found surprising?
KP: I have been studying fungus-resistant varieties, especially those adapted to Northern climatic conditions, for a few years now. What surprises me the most is the huge diversity we see in their aroma profiles, as well as how different they are from each other. I am also pretty amazed that there is so much to discover about these varieties.
CP: I work mainly with hybrid varieties, mainly American hybrids. I’m not particularly surprised to see differences and their specific characteristics. My research is mainly in the field and I study resistant grape varieties as any new grape variety regardless of whether it is resistant or not. I agree with Dr. Pedneault, for each new variety, there is a lot of research to do in order to well know the variety.