Grape (Wine & Juice Viticulture) Archives - Page 3 of 5

Heat stress in wine grapes: acclimation and potential mitigation

Post author:Abby Clayton-Gearing
Post published:October 20, 2023
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Heat stress poses challenges for the sustainable production of premium wine grapes in the Pacific Northwest. The intensity of heat waves has been increasing. For example, the series of heat wave events in 2021 broke temperature records in many locations in this region, and heat waves were again common during the 2022 and 2023 growing season. Growers need knowledge of how grapevines adjust to heat waves or sudden temperature changes to make informed management decisions. We grew potted grapevines in environmentally controlled growth chambers under different temperature regimes (simulating cool and warm growing seasons) before exposing the vines to sudden temperature changes with maximum temperatures varying from 77°F to 104°F. Photosynthesis measurements showed that grapevines might tolerate a sudden rise in temperature better in a warm than a cool season. During extended heat waves, however, the cool season-acclimated vines recovered faster than the warm season-acclimated vines.

Detection of wine faults using the electronic tongue

Post author:Abby Clayton-Gearing
Post published:June 29, 2022
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Faulted wines pose a serious economic problem to the wine industry, these off flavors can cause consumers, new to a region or variety, to reject that region entirely. Wine faults can include off-aromas or flavors associated with chemical compounds produced by spoilage organisms Brettanomyces, Acetobacter, Pediococcus or Lactobacillus. From the producers and winemakers’ perspective, early detection of wine faults would allow for remediation before the fault becomes more serious, intractable, and costly. Research in wine fault detection continues to develop as more sensitive and rapid analytical methods are identified that can reflect the complexity of the faulted wine.

Biology and Management of Cutworms in Washington Vineyards

Post author:Abby Clayton-Gearing
Post published:June 29, 2022
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Cutworms are capable of causing severe damage in vineyards during the early spring months when vines buds and tender shoots are at their most vulnerable. Damage to buds can cause severe crop loss in Washington vineyards, and this study supports the idea that the Cutworm species found on vineyard floors (on weeds, etc.) are a minor component of the fauna that actually damages grapevines. Vineyard sites with a large number of Cutworms on the vineyard floor did not necessarily sustain major bud damage. Conversely, sites with small numbers of Cutworms sometimes sustained major bud damage. This appeared to be related to ground cover presence/absence and/or type, but was also, in view of the rearing data, a consequence of most ground-dwelling species preferring to remain on the ground and not climb up grapevines.

Investigation of Potential Climatic and Nutritional Causes of Grape Chlorosis

Post author:Abby Clayton-Gearing
Post published:April 22, 2022
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Nitrogen levels in grape must that are either too high or too low can cause sensory and economic issues in the production of fine wine. The amount of available nitrogen during fermentation is key to the healthy formation and reproduction of yeast, and completion of the process to dryness. The major yeast strain that dominates healthy alcoholic fermentation, Saccharomyces cerevisiae, typically produces one molecule of urea, glutamate, and proline from the metabolism of the amino arginine.

Practical applications of stomatal conductance for optimizing irrigation

Post author:Abby Clayton-Gearing
Post published:February 1, 2022
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Plant-based estimations of vine water status using tools such as the Scholander-type pressure chambers, which measure leaf water potential, are currently employed by wine grape growers for irrigation scheduling. There is a need; however, for more time-efficient and less intensive methods that would diversify the irrigation scheduling toolkit. A portable leaf porometer measuring stomatal conductance to water vapor provides real-time data on current vine-water status rapidly and through non-destructive means, making it an appealing tool to irrigation scheduling. Three irrigation treatments were applied to a red (Merlot) and white (Chardonnay) cultivars of field-grown grapevines (Vitis vinifera L.) over three growing seasons to evaluate the effectiveness of porometry in determining the extent of water stress. These treatments included high irrigation (~~100% ETc), moderate irrigation (~~50% ETc), and low irrigation (~~25% ETc). From full-bloom through physiological maturity of grape berries, stomatal conductance and mid-day leaf water potential were recorded concurrently from a single leaf in each replication 4 to 6 days after the most recent irrigation.