For 2015-2016, the OWB allocated up to $314,824 for the support of these research grants. Below are the research project summaries and full reports.

Walter Mahaffee, Research Plant Pathologist at the Horticulture Crops Research Laboratory, USDA-Agricultural Research Service, Grape Powdery Mildew Management – A Fungicide Timing and Selection Conundrum

This research will improve the efficiency of grape production by optimizing fungicide selection and timing to manage powdery mildew of grape berries. There are several mobile fungicides that could be applied at specific inflorescence development stages to reduce the need for short application intervals while still improving disease control. This research will determine the most effective fungicide application timing with relation to grape inflorescence development/phenological stage and how their mobility impacts disease development.

Joe DeFrancesco, Assistant Professor, Senior Research, Department of Horticulture, Oregon State University, Pest Management Strategic Plan (PMSP) for Wine Grapes in Oregon

Joe DeFrancesco and assistant Katie Murray will be developing a Pest Management Strategic Plan (PMSP) for Oregon Wine Grapes that will help the industry identify short- and long-term pest management challenges, goals, and strategies for success. The PMSP will prioritize research, regulatory and educational needs and projects for the industry. The researchers will create a “work group” of key industry people (e.g. growers, consultants, researchers) who will help create a draft outline of the PMSP. The researchers will communicate in various ways with both work group members and other interested industry representatives to reach consensus about major pest management challenges and priorities. Once finalized, the Oregon wine grape industry can begin to use the PMSP as a road map to address specific and targeted pest management issues identified by the PMSP process.

Click here to view the PMSP for Wine Grapes in Oregon.

Patty Skinkis, Associate Professor and Viticulture Extension Specialist, Department of Horticulture, Oregon State University, Defining Crop Load Metrics for Quality Pinot Noir Production in Oregon

Do low yields result in better wine? Premium wine grape producers worldwide boast of low yields that concentrate flavors. This concept has driven yield management practices in Oregon, where specific yield targets are thought to produce superior wine quality. However, these targets are not scientifically founded and are universally applied, without considering differences in vineyard sites, design and vine health. The goal of this research is to develop improved metrics by which to evaluate quality in the vineyard and help growers refine yield management decisions. The project has been implemented in 15 Pinot noir vineyards in the Willamette Valley to determine how fruit yield influences vine growth, fruit composition and wine quality. Four sites are monitored more closely for vine physiological responses. Results indicate that vines can carry greater yields without compromising vine health and without having a major impact on basic ripeness parameters or phenolics at harvest. Vineyard site differences, not yield, represent the greatest difference in fruit quality in the study. Sensory analysis of wines is still pending, but vineyard data results suggest that growers and wineries can increase profitability by reducing crop thinning costs while maintaining optimum fruit quality.

Patty Skinkis, Associate Professor and Viticulture Extension Specialist, Department of Horticulture, Oregon State University, Impact of vine vigor, nitrogen, and carbohydrate status on fruitfulness of Pinot noir

Grapevines produce tiny fruit initials within their buds during the growing season in preparation of next season’s crop. The more grape clusters formed within the buds, the greater its “fruitfulness.” Growers depend on good fruitfulness to ensure sufficient yields for wine production. In some years, Pinot noir vineyards have been found to have low yields due to reduced fruitfulness and/or poor fruit set (number of berries that are developed). In other years, yields are very high due to high fruitfulness and/or fruit set, requiring significant labor costs to reduce crop level to achieve yield goals. This yearly variability creates problems in projecting vineyard management costs and potential profits. A two-year study was developed to understand the physiological nature of bud fruitfulness under varying vine vigor and nutrient levels. The project also includes leaf removal and lateral removal treatments to evaluate how typical canopy management practices affect bud fruitfulness. Results indicate that primary bud necrosis was rarely found and differences in fruitfulness appear to be due to vine leaf area or nitrogen status. Basal buds were found to be fruitful, which is contrary to common industry belief. As the data are analyzed in this project, we will gain a better understanding of how vine nutrient status and canopy management practices enhance or decreased fruitfulness. If methods can be developed to stabilize fruitfulness, growers will be able to achieve greater crop consistency, quality, and potentially greater profits.

James Osborne, Extension Enologist, Department of Food Science and Technology, Oregon State University, Formulation of volatile sulfur compounds in Pinot noir post-fermentation

The formation of volatile sulfur compounds in wine such as hydrogen sulfide (H2S) (rotten egg smell), mercaptans (rubber, garlic smells), and disulfides (cabbage, onion smells) can significantly impact wine quality and can be a challenge for winemakers to deal with. This project focused on the formation of these volatile sulfur compounds (VSCs) post-fermentation and potential causes. Results from the first year of this study indicated that the development of volatile sulfur aroma taints in wines undergoing barrel aging was due to formation of H2S and not to the formation of more complex VSCs. Additional research has shown that the concentration of yeast available nitrogen during fermentation as well as the type of nitrogen (inorganic vs. organic) influenced the formation of H2S and other VSC compounds. In particular, diammonium phosphate (DAP) supplementation increased the amount of H2S formed late in fermentation and resulted in the highest amount of other VSCs in the wines post-fermentation. The role of elemental sulfur in the formation of VSCs was also investigated. Sulfur is a commonly used fungicide in the vineyard but residual levels on grapes at harvest can result in H2S formation during fermentation. The concentration of elemental sulfur required to cause H2S issues as well as the impact of elemental sulfur on formation of other VSCs post-fermentation is not well understood. Concentrations of elemental sulfur of as low as 5 mg/g caused increased H2S production during Pinot noir fermentations. In addition, higher elemental sulfur additions resulted in higher H2S production late in fermentation and higher concentrations of other VSCs in the wines post-fermentation. To better understand what level of elemental sulfur may be on grapes in Oregon at harvest grape samples from collaborating wineries and vineyards were collected in 2014 and assessed for elemental sulfur concentration. Samples will be collected in 2015 and beyond so as to better understand the levels of sulfur on grapes over a number of seasons and what role this factor may play in causing issues with the formation of VSCs during winemaking.

Elizabeth Tomasino, Oregon Wine Research Institute, Department of Food Science and Technology, Oregon State University, Chiral Terpenes – Threshold Determination and Sensory Impact on Aromatic White Wines

Overall goal – This project is but part of a larger overall program investigating white wine quality and the relationships between chemical composition and sensory perception. Terpenes were focused on as the first group of compounds of interest due to their known importance on aromatic white wine aroma. These compounds are responsible for fruity, citrus and floral aromas of white wines. However they are chiral compounds (present in 2 forms) and these different chiral forms have different aromas and perception thresholds. Future work that builds from this project will investigate viticultural and winemaking procedures to chiral terpene content as well as further investigation into other white wine components that are preferred by consumers.

Objective 1-method development for chiral terpenes in aromatic white wines (completed)

A head space solid phase microextraction (HS-SPME) method using multidimension-gas chromatography has been successfully completed. This method is used to measure the chiral terpene content of aromatic white wines, specifically focusing on Pinot gris and Riesling. The chiral terpene profile of Pinot gris wines was related to place of origin. Chiral terpene profile of Riesling wines were also linked to place of origin, but were also effect by style and vintage. The paper that details the analytical method can be found at

Objective 2 – Sensory impact of chiral terpenes

Isomer excess (one isomer having a higher concentration than the other) has been determined (see report). Sensory tests will be used to determine if this isomer excess plays a role in sensory perception.

Objective 3 – Role of matrix to terpene perception

The matrix (nonaromatic portion of the wine) was found to impact the measurement of chiral terpenes. Therefore it is thought that the matrix may also play a role in sensory perception of these compounds. Sensory tests using a different “matrix” will be evaluated to determine if these components factor into the perception of these compounds.

Results from this project have been (or will be) presented at the 9th International Cool Climate Symposium, 250th National American Chemical Society and the 66th ASEV National conference.

Laurent Deluc, Assistant Professor in grape research at the Department of Horticulture, Oregon State University, Determine the impact of cluster thinning and cluster zone leaf removal on the hormone content of Pinot noir grape berry

Dr. Deluc’s group is leading a research project aimed to understand the effects of two viticulture practices (leaf removal and cluster thinning) on the accumulation of plant growth regulators (PGRs) during grape berry development of Pinot noir. Based upon our current data, we confirmed the coordinated accumulation of PGRs during critical phases of fruit development including the accumulation of auxins, gibberellins, and cytokinins during early stages of berry development, the “switch” between abscisic acid and auxin at the time of ripening initiation (véraison), a spike of ethylene during the same period, and the accumulation of several PGRs unrelated to ripening during the late stages of fruit development. We also observed a minor but substantial effect of the two viticulture practices on the dynamics of auxin and ABA during the ripening transition.

Vaughn Walton, Associate Professor, Horticultural Entomologist, Department of Horticulture, Oregon State University, Integrative studies of vector-related field epidemiology for grapevine red blotch-associated virus and grapevine leafroll-associated virus in Oregon

The temporal and spatial distributions of insects that are vectors of grapevine leafroll-associated virus (GLRaV) strains have been recently determined. Sweep net sampling and sticky card monitoring in viticulture production regions of Oregon in 2014 displayed the presence of several species of insects that may potentially vector grapevine red blotch-associated virus, including the grape leafhopper, Western grape leafhopper and potato leafhopper. Potential vector insects were systematically collected during 2014 in Oregon vineyards.  These samples showed a wide range of tentatively identified leafhopper species in all production regions.  Genomic tests of potential GRBaV insect vectors from California showed the presence of the virus in at least one of the suspected insect vector species present in Oregon collections (Zalom, pers. comm.).

Newly formulated PCR primers were used to determine the genomic status and spatial distribution of GRBaV together with that of GLRaV in Oregon vineyards. These results, however, still do not account for the sum of symptomatic vines. The distribution of both tested viruses suggests vector dispersal, but the differing distribution patterns found within vineyards suggest different vector insects are associated with each of the viruses. Currently no clarity currently exists for potential vectors of GRBaV, and as of yet detailed knowledge of field epidemiology of this disease is lacking. Specific to this topic, our data additionally indicate that GRBaV-infected plants are concentrated toward the edge of the sampled vineyards. Given this evidence, there may be a possible impact by insect vectors that may use alternate host plants.