Can Altering Canopy Shape Increase Productivity of Pinot noir: a new experiment at OSU’s Research Vineyard

Dr. R. Paul Schreiner, Research Plant Physiologist, USDA-ARS, Corvallis, OR

The newest block at Woodhall Research Vineyard is now six years old, and we will begin work in earnest next growing season to ask some fundamental production questions for Pinot noir. The key question is whether opening the top of a standard VSP training system (resulting in a Y-shaped canopy) will increase Pinot noir productivity without sacrificing quality (Figure 1). A second question is whether planting vines at a higher density impacts vine productivity or fruit quality. These questions are being addressed using a factorial experiment where two trellis treatments (traditional VSP & wide VSP) and two vine density treatments (3-foot and 6-foot in-row spacing) are applied in a randomized block design with five blocks. Each experimental plot has five continuous rows of vines about 100 feet long. Data will be collected from the middle three rows, allowing a border row of identical treatment on each side. Different crop levels will be applied to each of the trellis × density treatments by randomly assigning the north or south half of each plot to either low or high crop levels. The trellis and vine density treatments have been in place since 2015, and crop load will be manipulated for the first time next year. The vines were established using industry-standard practices (irrigation, fertilization, no crop in first two years, slowly increasing crop levels thereafter). In the last two years, vines were irrigated only twice each summer, when leaf water potential values reached about -1.4 MPa.

Why this design? Pinot noir producers in western Oregon use a VSP trellis system nearly exclusively where the shoots exist in a tight vertical plane that exposes only a small fraction of leaves to sunlight at midday when solar radiation is maximal. Opening the top of the trellis using a wide VSP system should increase net vine photosynthesis and the vine’s overall carbon budget, allowing more fruit to be produced per acre compared to a traditional VSP. This change can be implemented without removing the existing trellis, keeping costs low for this modification. A similar trellis design was shown to increase yield without compromising quality in Riesling vineyards (Reynolds et al. 1996). Pinot noir producers still thin crop to low levels, leaving 25-40% of their fruit on the vineyard floor. If opening up the canopy can allow Pinot noir producers to ripen more fruit per acre without negatively affecting quality, this approach can increase profits and sustainable production. Vine density per acre may also impact vine productivity or quality directly or by interacting with the altered trellis system. Still, such impacts cannot be predicted based on current knowledge. Since grafted grapevines cost about $5 each, reducing the number of plants needed per acre will significantly reduce establishment costs.

We have collected baseline data from the past five years. The block produced 2.2 US tons per acre in 2019 when the fruit was thinned to one cluster per shoot. Yield in 2020 was 2.5 tons per acre when no fruit thinning was applied due to low set in 2020. Thus far, yield has not been altered by the trellis or vine density treatments. However, vine vegetative growth based on pruning weights was altered for the first time in 2019. The high-density vines produced more shoot biomass in the wide VSP than the traditional VSP, but the low-density vines did not. Thus, the wide VSP appeared to capture more carbon than the traditional VSP in 2019, but only in high-density vines. We do not yet know if a similar response occurred in 2020 since pruning weights have not been obtained yet. Treatments have not altered yield parameters such as cluster weight and berry weight. Fruit composition based on must soluble solids, pH, titratable acids, and mineral nutrient concentrations has not been altered either. The application of different crop levels next year will result in a different yield, and this will begin to provide the true test of this experiment. I am excited to test these ideas on a large scale.

This research addresses improving vineyard production efficiency by altering the most common Pinot noir training system. If our hypothesis is correct, this research will improve Pinot noir wine grape growers’ profitability by increasing yield per acre, thus improving overall land and resource use efficiency.

Figure 1. Pinot noir in the Trellis Experiment at Woodhall Research Vineyard near midday on August 26, 2020. Top panel: Standard VSP. Bottom panel: Wide VSP. Note: larger shadow under Wide VSP vines.

Literature Cited

Reynolds AG, Wardle DA and Naylor AP. 1996. Impact of training system, vine spacing, and basal leaf removal on Riesling. Vine performance, berry composition, canopy microclimate, and vineyard labor requirements. Am J Enol Vitic 47:63-76.

Understanding the Economic Consequences of Smoke Events for the Oregon Wine Industry

James A. Sterns, Associate Professor, Applied Economics, OSU, jasterns@oregonstate.edu

With genuine concerns for the loss of life and property during this time of still-burning wildfires, I am also challenged by questions about the economic consequences of these fires for Oregon’s wine industry. With most grapes still in the vineyard, the potential for significant loss of this year’s harvest weighs heavily on vineyard managers throughout the state. The short-run answer, unfortunately, is frustratingly vague. It’s like I am trapped in an NPR radio broadcast of Michael Feldman’s comedy quiz show, Whad’Ya Know? Each episode begins with the show’s namesake and host asking his live audience that question, to which the audience replies in unison, “Not much!” 

This article has two goals – first, summarize and provide links to the limited amount of information that is available; and second, to outline suggestions for creating the necessary records, data sets and documentation that will allow us to be better positioned to answer questions about the economic consequences of future smoke events.

First, what do we know? Several websites provide one-stop sourcing of available information. These include the Oregon Wine Board Wildfire Smoke Toolkit webpage and the University of California-Davis Wildfire and Smoke Exposure Resources website. Another comprehensive source of information is available from the Australian Wine Research Institute, which has been very active in recent years in supporting research on how smoke events can affect wine grapes and wine making.

These and other sources (reference links throughout this article) help frame questions about the overall consequences of smoke events. Still, in general, economic impacts are not addressed in any detailed manner. That type of substantive research-based information is still needed. As Associate Professor Elizabeth Tomasino and her colleagues reported in the August 2020 Vine to Wine issue, plans are in the works for grant-funded research on this topic. Their first step was to conduct a needs assessment with industry stakeholders, which included a shortlist of research topics related to smoke events’ economic impacts. As that research moves forward, one of the key constraints will be the availability of data from Pacific Northwest vineyards and wineries. Vineyard managers and wine makers can help resolve this ongoing challenge. Here are a few suggestions for how to help by documenting what is happening now and keeping records of this information for future reference.

Data needs for Estimating Economic Consequences in Vineyard and Wineries:

Weather & Air Quality Data – Keep track of your local smoke event data, which may be simple observational data (e.g., dates and duration of when you can smell smoke in your locality). Alternatively, some vineyards may have contracted with private farm management service providers, and in some instances, these providers have installed weather sensors. If this is the case, then the key is to archive in an easily accessible database detailed daily wind, temperature, humidity, and air quality readings as site- specific as possible. Understanding “trigger” levels of exposure that lead to smoke compounds in wines can become the basis for future vineyard management decision making. This starts with our ability to link vineyard conditions with test results of smoke contamination in wine crushes.

Variable, Fixed, and Total Costs – I often ask my students if it is ever a good idea to keep farming when losing money. I am trying to have them understand that a decision to go idle for a season or not harvest a crop will still have fixed costs to be paid. The choice to lose money is relative, so the better question a manager needs to ask is, “Which option will involve the least amount of loss?” In terms of this year’s grape harvest, can a vineyard manager hope to make enough from a harvested crop to cover all the variable costs associated with that harvest plus cover some of the fixed expenses that will always need to be paid? If so, then that’s the better choice. If the harvested crop’s value is less than the sum of variable costs of harvesting it, then obviously, it’s better not to harvest. In terms of data to be tracked, keeping detailed estimates of fixed and variable costs will not only help with decisions that must be made now, but also this financial information can be evaluated in a broader context for future smoke events. If enough vineyards track these costs, that data could be collected and aggregated anonymously, and then financial benchmarks could be established for making more informed decisions in years to come.

Dump, divert, or distill – A current recommendation for vineyard managers is to conduct small lot fermentations (a.k.a. micro-ferments or bucket-ferments) on grapes that have been exposed to smoke. Should results from these tests indicate that the grapes are unusable for wine, there are still managerial decisions to make. Once again, cost and price data are needed to inform this decision. Option one is to dump the grapes in the vineyard, either in the near future, or possibly waiting until pruning. Both options have vineyard management issues, but also economic ones. For example, what are the labor (and possibly machine costs if mechanically harvested) to dump the grapes now compared to potentially higher pruning labor time and costs if the grapes are left on the vine until then? Another possibility – grapes have nutritional value as animal feed. Could harvested grapes be sold to a neighboring livestock operation? And more importantly, what is the price the neighbor is willing to pay and is that price high enough to cover harvesting costs? A third option might be to use the grapes for distilling alcohol for the hand sanitizer market – a new market opportunity that has emerged during the COVID-19 pandemic. Again, the critical issue is the potential market value of the smoke-affected grapes for use as an input in this alternative product market.

Market responses, on inventory and current year crop – Another key area of data to track will be the market responses to these wildfire events. Two prices to track and record will be the value of any residual 2019 harvest in inventory, such as bulk wine. If this year’s smoke events leave wine makers shy on volume, will this lead to a price increase in the value of that inventory? If so, that is an economic consequence to document. Similarly, depending on the severity of this year’s smoke event, grapes grown in 2020 that are unaffected by smoke may see a price increase. Again, documenting any smoke-event driven shifts in prices will be critical for future work in estimating economic consequences.

Consumer responses, on-site and online – The COVID-19 pandemic complicates the analysis, but there still needs to be data collected about how winery customers are responding to the wildfires. On-site tasting room visits, which were already diminished by social distancing and other public health measures, will be further eroded by the wildfires. Collecting data on declines in visitations attributable to the wildfire will help future analyses. Similarly, tracking online sales, especially if consumers are shifting their buying habits, is also needed. Will consumers buy more of the current inventory in fear of future shortages? What are wine club members asking you during this time? Tracking their concerns and questions may be early indicators of how future sales of the 2020 vintage will be impacted. Aggregating these data, even if the overall effect on demand is negligible, will provide vital information for future analysis and forecasts of smoke events’ economic consequences.

Insurance Costs and Compensation – A final area of data that is needed concerns crop insurance. Data on insurance premiums paid by vineyards are needed. Even if a vineyard or winery opted not to purchase crop insurance, records of insurance companies’ quotes for proposed premiums are valuable for future analysis. Also needed are the costs of checking for potential, and if needed, proof of damage (e.g., costs of testing for smoke compounds and any other expenses of documenting the damage and certifying rejected sales). Finally, records about the amount of financial compensation received, should an insurance claim be paid will be important for future economic analysis. This should include any details about factors that affected the overall level of compensation (for example, some insurance policies will adjust claims and reduce the amount of payment if a vineyard is not harvested).

As we look to the future, we can anticipate a need for a better understanding of how wildfires and smoke events can affect the Oregon wine industry’s economic viability. Tracking and recording what is happening now, as decisions are being made in vineyards and wineries, will be vitally important sources of information for future research. With resiliency, the Oregon wine industry will emerge from the tragedies of this wildfire season. Let us work together to ensure that we can do better in the future by learning through our current adversities.

Avoid mixing biologicals with antimicrobials

Dr. Jay W. Pscheidt and Lisa Jones, Dept. of Botany and Plant Pathology, Oregon State University

Actinovate AG (Streptomyces lydicus WYEC 108) and many other biological products are used in the management of organic grapes. Tank mixing more than one product is both economical and time-saving but tank mix compatibilities with biological control products such as Actinovate have not been thoroughly evaluated. In 2016, we examined the tank mix compatibility of Actinovate AG with commonly used organic products.

Actinovate AG was prepared at a concentration of 0.1g/ml. A 300 ml solution of Actinovate was prepared in a 500 ml beaker then mixed with each material and allowed to stand for 30 minutes. The mixture was then plated onto agar and incubated for 7 days at room temperature. The number of colony-forming units (CFU) of S. lydicus exposed in each mix was assessed daily and compared to an Actinovate plus water only control. The percentage of S. lydicus CFU in each tank mix compared to the CFU in the Actinovate control was calculated.

An average of 3.2×105 S. lydicus CFU developed after 7 days incubation on the various media when Actinovate was just mixed with water. Several products inhibited the growth of S. lydicus when prepared in as a mixture in the laboratory. No growth of S. lydicus was observed on plates when Actinovate was mixed with Horticultural Vinegar, a high rate of Regalia, Rex Lime Sulfur, Serenade Optimum, or Solubor DF. Less than 10% of the S. lydicus CFU grew when Actinovate was mixed with Biomin Calcium, Botector, Neptune’s Harvest 2-4-1 fish fertilizer, or Thuricide. Significantly fewer S. lydicus CFU grew when Double Nickel, the low rate of Regalia, Serenade Max, the high rate of Stimplex or Toggle were mix with Actinovate. There was no significant difference in the number of S. lydicus CFU that grew when Zen-O-Spore was mixed with Actinovate. The number of S. lydicus CFU was greater than double (219%) or quadruple (482%) that of the Actinovate control when mixed with Nitrozyme or the low rate of Stimplex, respectively.

Many of the biological products in this study grew quicker than S. lydicus under laboratory conditions. These fungi or bacteria generally outcompeted S. lydicus for space and resources on the agar plates. The fungus found in Zen-O-Spore was slower to grow and did not outcompete S. lydicus during the 7-day incubation.

This data does not imply a lack of or enhanced disease control in the field. For example, blueberry field trials over a 2-year period where Actinovate was mixed with Simplex did not result in disease control that was different than when either product was used alone. The data does indicate incompatibility between various products used in organic production.

For a complete data set please visit: http://sites.science.oregonstate.edu/bpp/Plant_Clinic/Fungicidebooklet/2016/Blueberry3.pdf

What’s New with Malolactic Fermentation

Dr. James Osborne, Associate Professor and Enology Extension Specialist, OSU

The malolactic fermentation (MLF) is a vital step in the production of cool climate red wines as well as some white wines. But despite its importance, MLF often gets taken for granted and just considered a step to reduce wine acidity. However, MLF is much more than just a biological de-acidification process and can have a number of other impacts on wine quality. Our lab has been conducting a number of projects over recent years investigating various aspects of MLF. One project is investigating interactions between Oenococcus oeni and the spoilage yeast Brettanomyces bruxellensis. An interesting result from this study was discovering that some O. oeni strains were capable of increasing the concentration of the volatile phenol precursors p-coumaric acid and ferulic acid. These pre-cursor compounds are found in grapes and wine mainly bound to a tartaric acid and in this form are not utilized by Brettanomyces. However, some O. oeni strains can remove the tartaric acid through the action of an enzyme, cinnamic esterase, and release free p-coumaric and ferulic acid that Brettanomyces can then metabolize to 4-ethylphenol and 4-ethyl guaiacol. This finding has led to the labelling of many commercial O. oeni strains as either cinnamic esterase (+) or (-) with the recommendation being to avoid use of cinnamic esterase (+) strains in situations where the wine may be at risk for Brettanomyces spoilage.

An additional area of research has been determining the effect of MLF on red wine color. We know that MLF changes wine pH which can cause a shift in red color, but were there other impacts on color due to MLF? Our lab demonstrated that independent of pH change, MLF results in a loss of color and lower formation of polymeric pigments. Results from a number of studies showed that this color loss was likely due to the metabolism of acetaldehyde by O. oeni. Acetaldehyde plays a key role in the development of polymeric pigments and so metabolism of acetaldehyde during MLF reduced formation of these color compounds. Delaying MLF was shown to help mitigate this color loss but delaying MLF for long periods is risky from a microbial spoilage point of view, as SO2 cannot be added to the wine until MLF is complete. Additional strategies to mitigate color loss due to MLF are currently being explored. One such strategy is the use of ML bacteria that do not metabolize acetaldehyde. To date, all O. oeni strains screened can metabolize acetaldehyde but other lactic acid bacterial species such as Lactobacillus look more promising. There has been renewed interest in using certain Lactobacillus species and strains to conduct MLF. In particular, homofermentative species of Lactobacillus have been studied as potential ML starter cultures. These bacteria do not produce acetic acid from glucose metabolism and so could be used for conducting concurrent alcoholic and malolactic fermentations without the risk of increased acetic acid. Currently, there are commercially produced L. platarum cultures available outside of the USA for use in winemaking. However, at this time these cultures are not available for winemaking use in the USA. The use of concurrent alcoholic and malolactic fermentation is one final area our lab has been studying. While there are obvious time advantages to conducting alcoholic and malolactic fermentation at the same time, there are still some concerns over the impact on wine quality, particularly for red wines. We recently completed a study investigating how the timing of MLF impacts Chardonnay aroma and mouthfeel and will be continuing work in this area focused on concurrent fermentations of red wines. As we continue to study malolactic bacteria, we are gaining a better appreciation for the impact they can have on wine quality and potential new strategies for their use. For additional information on any of the studies we have conducted on MLF please contact me at: james.osborne@oregonstate.edu

Pest Alert: Grape Cane Borer

Dr. Patty Skinkis, Professor and Viticulture Extension Specialist, OSU
Dr. Vaughn Walton, Professor and Horticultural Entomologist, OSU

There have been an increasing number of reports of grape cane borer presence and damage in vineyards throughout the Willamette Valley this winter. Typically these reports during the bud break period in April when adults are active and evidence of shoot dieback occurs. However, we have received numerous reports this January and early February as growers begin pruning. This observation may be due to various factors including more suitable weather conditions (winter and summer), higher levels of populations surviving, more suitable host plant materials, increased awareness and improved monitoring. The borers can have a long life cycle within the vine, living as larvae (grubs) within the shoot or cane for nearly one year. Adults lay eggs during early spring and hatch and develop into larvae that feed on the shoot tissues during the growing season. They remain in the wood as pupae during winter and may be found when pruning commences. Both pupae and adults have been reported in southern and mid-Willamette Valley vineyards this winter. This article covers the most salient points for your awareness this winter; please consult additional resources below for further details.

What to look for in the vineyard:
Galleries burrowed by larvae can be observed in cane tissue usually in older or dead wood, canes, spurs, or cordons. These holes are round, drill-like holes of ~0.4 mm diameter, and they are often accompanied with sawdust that was produced by the adult when burrowing into the shoot during late summer or early fall the year prior. Cutting into the wood near these holes during pruning will likely reveal a pupa that is 1-8 mm in length (<0.3 in).

Management:
Insecticide application is often difficult to apply during the dormancy period due to the difficulty for the application to reach the pest and the inability to get into the vineyard with equipment. There are biological controls, such as the Steinernema carpocapsae, an entomopathogenic nematode, that may be used, but care needs to be taken to ensure that the product is handled properly and applied to the entry points of the pest to be effective. In some cases, the best method will be to cut out any canes that have the burrow holes evident. Remove pruning wood, as the wood contains the pupae that will emerge in spring. Removing the pest from the vineyard will ensure that a population does not exist to allow new infestations into tissues.

For more information about the cane borer, please see the following resources:

Oregon State University Receives Gift of the Artist

Ashland artist, Betty LaDuke, has generously gifted Oregon State University College of Agricultural Sciences three paintings to the Art About Agriculture program in commemoration of Dr. Porter Lombard, OSU Emeritus Researcher. Dr. Lombard’s contribution to the Oregon wine industry is immeasurable.

Dedicated to Porter Lombard for his pioneering work at Oregon State University in developing the Oregon grape industry, and beyond. And, for five decades of professional and personal friendship shared with my husband – Peter Westigard, an OSU Entomologist – and our families.” – Betty LaDuke, 2019

Betty LaDuke (née Bernstein) was born in 1933, The Bronx, New York City, to Jewish immigrant parents from the Ukrainian Soviet Socialist Republic and Poland. She grew up in an ethnically diverse neighborhood where early influences in her arts education included classes taught by distinguished African-American artists, Elizabeth Catlett and Charles White. College scholarships led LaDuke to study art at Denver University (1950), the Cleveland Art Institute (1951), and at the Instituto Allende in San Miguel, Mexico (1953- 1954). In Mexico, she explored the diversity and heritage of the region, as well as visited the studios of prominent Mexican muralists Diego Rivera, David Alfaro Siqueiros, and Rufino Tamayo. LaDuke founded her professional artist studio practice in Guanajuato, Mexico, and lived for one year with the indigenous Otomi people of the Ixmiquilpan Region where she painted murals that depicted Otomi heritage. In 1956, Betty LaDuke returned to the United States, where she met Sun Bear (Vincent LaDuke), gave birth to her daughter (activist community organizer Winona LaDuke (b. 1959)), and earned her Master’s Degree from Los Angeles State College (1963). In 1964, Betty and Winona moved to Ashland, OR where she taught in the Art Department at Southern Oregon University until retiring Professor of Art Emeritus in 1996. Betty LaDuke married Oregon State University Entomologist, Peter Hughes Westigard (1933–2011) in 1965, and had her son, Jason Westigard in 1970. In 1972, a sabbatical from teaching enabled LaDuke to spend a month in India sketching the people and their connection to nature, food production, and heritage; a trip that inspired annual travels throughout Asia, Africa, and Latin America that focused on sketching the experiences of indigenous women, their cultural heritage, and agricultural practices. LaDuke captured these experiences and sketches in numerous books, including Compañeras: Women, Art, & Social Change in Latin America (City Lights Books, 1985), Women Artists: Multi-Cultural Visions (Red Sea Press, 1992) and Africa: Women’s Art, Women’s Lives (Africa World Press, 1997). LaDuke’s work with Heifer International’s study tours from 2003 to 2009 culminated in the Dreaming Cows series of sixty-two artworks and the book, Dreaming Cows: The Paintings, Murals and Drawings of Betty LaDuke by Susan Jo Bumagin (Heifer International, 2009). LaDuke donated the series to Heifer International’s World Headquarters in Little Rock, Arkansas.

Betty LaDuke’s artworks can be found in many public and private collections throughout Oregon, including Coos Art Museum, Grants Pass Art Museum, Hallie Ford Museum of Art, Jordan Schnitzer Museum of Art, Pacific University, Portland Art Museum, Rogue Valley International Airport, Southern Oregon University, and the Art About Agriculture Permanent Collection (College of Agricultural Sciences, Oregon State University). LaDuke was the recipient of Oregon Arts Commission’s 1993 Governor’s Arts Award for individual contribution to Oregon culture, and the United States Society for Education Through Art 1996 Ziegfeld Award for distinguished leadership in arts education.

Bountiful Harvest
In 2010, Betty LaDuke was invited to observe and sketch the flower harvest at La Mera Gardens (Fry Family Farms) in Talent, Oregon. This experience served as an awakening to the marvel of local agricultural production and the people that make it possible.

Sketches from regular visits to the Fry Family Farms blossomed into numerous large paintings on shaped and routed plywood panels that celebrate the dignity and pride of farmworkers during all phases of agricultural production across a wide variety of produce. In 2012, the Rogue Valley International-Medford Airport acquired Celebrating Local Farms and Farmworkers, a selection of twenty-six panels, for permanent display. Betty LaDuke’s 2016 book, Bountiful Harvest: From Land to Table (White Cloud Press) shares her artworks and story along with stories from agricultural workers, orchard and vineyard owners, and the Ashland Food Cooperative.

Grape Planting
Betty LaDuke’s Grape Harvest, 2015, a triptych of acrylic paintings on shaped wood panels, was generously gifted to the College of Agricultural Sciences for permanent display within the Department of Horticulture in commemoration of Oregon State University Emeritus Researcher, Dr. Porter Lombard. Dr. Lombard’s contribution to the Oregon wine industry is immeasurable. The three panels comprising Grape Planting originated from sketches from Quail Run Vineyards, Roque Valley, Oregon, with guidance and support from the General Manager, Michael Moore. Grape Planting, 2015 was accepted into the Art About Agriculture Permanent Collection by the 2019 Art About Agriculture Advisory Council and co-sponsored by the Office of Institutional Diversity.

GIFT of the ARTIST, in commemoration of Dr. Porter Lombard, Emeritus Researcher in Horticulture at Southern Oregon Research and Extension Center (1962-1980) and Oregon State University, Corvallis (1980 to 1992)
Art About Agriculture 2019
Co-sponsored by the Office of Institutional Diversity

Abnormal Spring Growth Patterns Observed in Spring 2019

Dr. Patty Skinkis, Viticulture Extension Specialist & Professor, Dept. of Horticulture, OSU

Our OSU Viticulture Extension team has been receiving numerous inquiries about delayed and stunted shoot growth this spring, primarily from western wine production regions of the state. Bud break occurred in mid- to late April for most vineyards in the region, which is considered normal. The region experienced frost events in the last few days of April and beginning of May that affected some vineyards from the Willamette Valley down to the Umpqua, Rogue, Applegate and Illinois Valleys of southern Oregon. Questions started coming in during May as growers began reporting delayed bud break and lagging shoot growth across western Oregon. Many of these growers did not report any frost damage from the late April frost events.

Symptoms reported by growers included the following:

  • Delayed and sporadic bud break in cane pruned vines, with greater delay in growth at mid and distal cane positions.
  • Stunted or delayed shoot growth, often noticed in shoots on the mid-cane node positions
  • Shoots with only inflorescences and no shoot tips on vines with healthy shoots
  • Symptoms were reported for both young and mature vines.

Observations by Region

Umpqua Valley.  Steve Renquist, OSU Extension Horticulturist in Douglas County, reported more issues in the northern half of Douglas County, primarily in higher elevation sites and hilltop areas of vineyards. Affected vineyards had uneven vine growth and some vines not breaking bud at all, primarily for Spanish and Rhone cultivars, many of which break bud earlier than cool climate cultivars. Canes had green cambium but buds were not pushing, and healthy shoot growth was primarily coming from suckers at the head and trunks of vines. He attributed the symptoms to cold damage caused by prolonged cold weather for two weeks in February combined with persistent snow cover. This time period was also characterized windy, cold nighttime conditions that may have led to further damage.

Southern Oregon. Alex Levin, Assistant Professor at the OSU Southern Oregon Research and Extension Center in Central Point, reported strange early season growth that was suspected to be due to the post-bud break frost events. However, the symptoms differed from typical frost damage and was not found only in low lying areas of vineyards. The problem was most prominent in Pinot noir compared to other cultivars in the region. Growers reported delayed bud break, stunted shoot growth, shoots with no shoot tips, buds that grew flower clusters with no shoot or minimal shoot (Figure 2), and leaf cupping with blackened/necrotic lesions of the leaf blade-petiole juncture (Figure 3). However, by late May, vine growth improved with warmer temperatures and lateral shoot push. It is unclear what caused these symptoms, but they align with those associated with Pinot Leaf Curl, a physiological disorder reported in California.

Figure 1. Stunted shoots and blind buds on 6-year-old Tempranillo vines in late May 2019 in Douglas County. Shoots at the head and trunk of the vine are growing normal. Photo received from grower via an OSU Extension inquiry.
Figure 2. A cane pruned Pinot noir vine from the Illinois Valley showing symptoms of stunted shoots with inflorescences growing from the cane and normal looking shoots growing from the head of the vine. Photo received via an OSU Extension inquiry.
Figure 3. A young Pinot noir shoot from a southern Oregon vineyard that has cupped leaves and blackened areas of the leaf petiole and veins (leaf to the left of the main shoot above). Photo received via an OSU Extension inquiry.

Willamette Valley. There were fewer reports of delayed bud break and stunting in the Willamette Valley than in the southern reaches of the state. However, similar symptoms were reported. In some cases, vineyards with delayed growth were linked to frost damage, vine nutrient stress, or trunk disease. In several cases, the cause of the problem was likely related to a compounding effect of vine stress over several seasons. The dry 2018 growing season took a toll on vine growth that may be manifesting symptoms this season. In examining data over multiple sites and multiple seasons in one of my research projects, I found that pruning weights were lower in 2018 than in the past six seasons (Figure 4). The pruning weights ranged from 0.07 to 0.16 lb/ft across the vineyards, which is lower than the 0.2-0.4 lb/ft that is considered optimum range for plant vigor. Most people reported having full canopies during 2018 that required less hedging; this may suggest fewer carbohydrates were stored in reserves by the post-harvest period.

A lack of reserve carbohydrates and nutrients may lead to reduced shoot growth in spring, as the vine is relying on stored resources for growth after bud break. If a vine is compromised in some way (e.g. trunk disease, crown gall, water stress, etc.) low carbohydrate reserves can further exacerbate issues with early season growth. It is possible that other areas of the state experienced similar declines in grapevine growth in 2018 that may play a role in what is being manifested as 2019 erratic spring growth. Exploring your own historical pruning weight data will help determine if you see a similar trend for 2018.

Figure 4. Dormant vine pruning weights of vineyards in the OSU Statewide Crop Load Project from 2012-2016. Means are presented for all sites in the study for each crop year. Data are from 12-15 vineyards per year. All vineyards are located within the Willamette Valley.

Weather considerations

Weather also needs to be considered as a factor affecting growth this spring. The 2018-2019 winter was mild until February which brought colder temperatures to most of the region. Mean daily temperatures for the month of February ranged from 36 to 38°F across western Oregon which are 5-6°F lower than the long-term averages for February. The rest of the dormant period (Nov-Mar) differed from the long-term averages by ~1-2°F. Despite being cooler in February, the minimum daily temperatures observed in February in western Oregon (29-33°F) were not within the range known to cause damage to dormant grapevines. However, the temperatures may have caused some tissue damage for vines in ecodormancy, the state at which vine tissues begin to deacclimate for spring. Grapevine tissues (phloem, buds, and xylem) become more sensitive to cold temperatures in the deacclimation phase and can be damaged at increasing temperatures (Ferguson et al. 2011). Fluctuating daily temperatures lead to changes in the vine’s cold hardiness (e.g. low temperature tolerance). The warmer conditions in January may have led to vine deacclimation, leaving tissues more sensitive to temperatures in February. Cool climate cultivars have quicker deacclimation and earlier bud break (Ferguson et al 2014) that may leave them more vulnerable to damage late winter than other cultivars.

Research conducted at OSU described the chilling requirements for Pinot noir to transition to different stages of dormancy and the temperature thresholds that would damage buds at the quiescent stage through to early growth stages. The results showed that 50% of the buds were damaged  (LD50) at 6.8 °F, 25.8°F, and 28.0°F for the quiescent, bud swell, and bud burst stages, respectively (Gardea 1988). Another study showed a threshold of 300 cumulative chilling hours to reach ecodormancy in Pinot noir (Gardea 1992). The more chilling that was received during dormancy led to more even bud break in that study. There is also the potential that low temperatures in winter and early spring to affect cell growth and development without causing death of the bud or vascular tissues. Cool winter and spring temperatures can influence vine growth and lead to slowed shoot development, deformed leaves and other physiological disorders that are not well described.

Although temperature data that is available from regional weather stations, such as AgriMet, do not indicate concerning temperatures, check temperature data from on-vineyard weather stations, if available. Fluctuating warm and cold temperatures in late winter, particularly in the January to March period, may explain one potential factor related to irregular growth you may be seeing in your vineyards. Be sure to check the cold temperatures for late April and early May, as post-bud break frost events occurred across western Oregon. These frost events may have also led to some tissue death or irregular growth.

Summary

There are many factors that can lead to delayed bud break and stunted vine growth in spring, including trunk disease, tissue damage due to frost or cold temperature events, nutrient deficiency, vole damage, rust or bud mites, and herbicide damage. However, the delayed growth and stunting reported in vineyards this spring seems to be somewhat consistent across the western region of the state, suggesting an abiotic factor. The weather conditions during late winter and early spring may have played a role in addition to underlying factors that influence vine health and productivity. To learn more about causes of stunting and delayed growth or about cold hardiness of grapevine tissues, be sure to explore the online resources below.

Further Reading

Literature Cited

Ferguson JC, Tarara JM, Mills LJ, Grove GG, Keller M. 2011. Dynamic thermal time model of cold hardiness for dormant grapevine buds. Ann Bot 107 (3) 389-396.

Ferguson JC, Moyer MM, Mills LJ, Hoogenboom G, Keller M. 2014. Modeling dormant bud cold hardiness and bud break in twenty-three Vitis genotypes reveals variation by region of origin. Am J Enol Vitic 65: 59-71.

Gardea AA. 1988. Freeze damage of Pinot noir (Vitis vinifera L.) as affected by bud development, INA-bacteria, and a bacterial inhibitor. MS Thesis. Oregon State University.

Gardea AA. 1992. Water partitioning and respiration activity of dormant grape buds. PhD Thesis. Oregon State University.

OSU provides online research and technical information for the Oregon wine industry

Dr. Patty Skinkis, Associate Professor and Viticulture Extension Specialist, Dept. of Horticulture, OSU

Members of the Oregon Wine Research Institute (OWRI) at Oregon State University work hard to provide you with current information on research that is in progress and provide access to research-based best management practices for vineyards and wineries. We have two online resources for your use, and they serve specific purposes:

The OWRI website
This website allows you to learn more about the research activities of OWRI. You will find research that is advancing wine industry knowledge or the fields of plant and food sciences. We provide newsletters, webinar videos, and articles about the research. Visit this site to learn how you can join our outreach events throughout the year.

The OSU Extension website
Oregon State University Extension faculty make technical information available for use by commercial growers and winemakers. This website is designed to help you troubleshoot vineyard or winery issues using unbiased, science-based information. To browse relevant content, click on “Crop Production” then “Wine Grapes” or “Food” then “Wine, Beer, Cider, and Spirits”.  Alternatively, you can use these direct links for wine grape and winery content.  

There are many agriculture Extension faculty throughout the state who provide online content in areas such as water, soils, pests, diseases, integrated pest management (IPM), marketing, and more, so be sure to use the site’s search feature. If you cannot find the information that you need on the OSU Extension website and want to consult with an Extension expert, use the website’s Ask an Expert form. Questions are routed to the appropriate Extension faculty (Skinkis, Osborne, Kaiser, Walton, etc.). Please note that this website is new, so more content will be added in the coming months.

Please visit these websites and give us feedback! Contact Denise L. Dewey with comments/feedback about the OWRI website. Contact Patty Skinkis (viticulture) or James Osborne (enology) for feedback on the OSU Extension website.

Vole Damage in Vineyards

Dr. Patty Skinkis, Associate Professor and Viticulture Extension Specialist, OSU 

I received a number of reports of vole damage in vineyards throughout the Willamette Valley this season. Evidence of their presence became visible in August with feeding damage to trunks (Figure 1) and within the canopy, including damage to shoots and rachises of grape clusters (Figure 2). Voles eat vegetation and typically feed on roots or the base of trunks. Voles do not typically cause issues until a population peak and/or environmental conditions allow for habitation. They may reach epidemic-level populations every ten to 12 years, but these population surges are not predictable and last for one year (Gunn et al. 2011). The Willamette Valley’s last reported vineyard infestation occurred in 2005, and some vineyards lost vines due to the damage.

Preventing and eradicating voles.  Our best suggestions to growers who have been observing vole presence in vineyards has been to encourage eradication. Trapping or baiting voles may not be practical on large acreage or advised with certain farming certifications. For example, zinc phosphide is not allowed in organic production. However, soil tillage or mowing may provide some level of prevention and control. Research in field crops show that tilling the soil is the most effective method of reducing vole populations (Jacob 2003), by disturbing their burrows and causing movement to other vegetated areas. Voles avoid bare ground, so tillage can prevent habitation altogether. In the Jacob (2003) study, they found voles disappeared altogether after disking to a depth of 19 inches. Mowing vegetation was found less effective than tillage, as the mulch from mowing allowed sufficient cover for the voles and did not encourage movement away from the cropped areas. Avoiding mulch layers or vegetation growth under-vine will prevent voles from inhabiting the areas near grapevine trunks and feeding on roots and trunks when food sources are limited.

Scouting for damage. Voles tend to feed on vine roots and at the base of trunks. Look for feeding damage at and just below the soil surface. Since the feeding typically occurs through the phloem and vascular cambium, the cell layers that lie between the phloem to the exterior and xylem to the interior, the vascular system is compromised. As a result, affected vines may turn color abruptly (yellow or red, Figure 3), as they have limited ability to move photosynthates (sugars) and mineral nutrients through the vines to the roots once the phloem and cambium are damaged. Roots are actively acquiring carbohydrates and mineral nutrients from the canopy during late season in preparation for the next year. Having this connection severed is a major issue.

Can anything be done to repair damaged vines? Vines with girdled trunks and root damage may not survive if the damage is done to the circumference of the vine. This is due to the lack of vascular cambium to grow new phloem tissue and “heal” the wound. The best thing to do at this time is flag vines with damage now and check back later in winter during pruning and early spring. If damage was only apparent in the canopy (rachises, berries, and shoots), vines may be able to be pruned to healthy tissue in winter. However, also be sure to flag these vines for follow-up.

Because voles do not hibernate, high populations this winter may pose a threat to vines if they continue feeding in areas where they were observed this season. It will be important to remove vegetation by way of tilling soil or removing mulch layers or vegetation under-vine to avoid any further damage.

Literature Cited

Gunn D, Hirnyck R, Shewmaker G, Takatori S, and Ellis L. 2011. Meadow voles and pocket gophers: Management in lawns, gardens, and cropland. University of Idaho, PNW 627.

Jacob J. 2003. Short-term effects of farming practices on populations of common voles. Ag Ecosyst Environ 95:321-325.

 

Figure 1. Vole damage to the base of a trunk on a mature grapevine. Photo courtesy of Ryan Wilkinson.

 

Figure 2. Feeding damage is apparent on the top of the grape cluster’s rachis (peduncle) and the lower portions of the shoot from which it originates. Photo courtesy of Ryan Wilkinson.

 

Figure 3. Vines with vole damage to the trunk show almost complete reddening of the canopy in Pinot noir vines. Photo courtesy of Ryan Wilkinson.

 

Resistance is Futile? Strobilurin resistance presence and persistence

Dr. Walt Mahaffee, Research Plant Pathologist, USDA- ARS

In 2015, we found widespread Strobilurin (QoI) resistance in Oregon, and subsequently in California and Washington when we surveyed viticulture regions in those states, it probably seemed like the sky might be falling.  Then when we showed that greater than 70% of the QoI resistant population was tolerant to very high doses of DMI (higher than can be legally applied); it really seemed like the sky would fall.  However, there was a silver lining. We kept all the DNA from all the inoculum monitoring (spore trapping) we had been doing since 2007.

We analyzed all those samples for presence of the genetic mutation responsible for the QoI resistance and found some interesting results. First, we weren’t able to detect QoI resistance before 2013. Second, we detected QoI resistance at least two years prior to growers reporting management problems. This means we had a tool to monitor resistance development which could be useful for warning growers of resistance developing.

Another remarkable finding was that the number and frequency of detecting resistant spores was much lower than the wild-type spores even when QoIs were being used in the vineyard, and we found far more resistant colonies than wild-type on leaves.

These results indicated that there might be a fitness cost to the mutation causing QoI resistance. Given that the mutation alters a protein involved in fungi producing energy, it makes sense that the fungus would not grow as well. This should also mean that moving away from using QoIs should allow the wild-type to out-compete the QoI resistant isolates, and eventually QoIs would become effective management tools again. Sarah Lowder, a PhD student, also made another discovery this past winter – Chasmothecia (the mildew overwintering structure) of QoI resistant populations do not survive as long as wild-type populations. This is more good news.

Now the big question is how to determine how long we need to rotate away from using chemistries with resistance and how to determine when we can use them again. That will be the future work of three graduate students in the lab.

Sarah is going to be working on how to rapidly and efficiently monitor for resistance. She has already made significant advances in this area. Sarah’s work this summer shows that we can swab worker gloves after manipulating the canopy (e.g. shoot thinning, lifting wires, leaf pulling, dropping crop, etc.) and get estimates on the presence of mildew and its resistance. These results are similar to spending hours scouring for mildew colonies. Sarah also developed a simple procedure to test for potential resistance by collecting bark in the winter. Simply grab bark off several vines and stuff it into a mason jar, add ice cold bottled water, shake, then decant through mosquito netting. The material adhering to the net can then be processed using our molecular assays.

Next, Chelsea Newbold (a new MS student) will be examining how the QoI resistance mutation impacts colony formation and sporulation in relation to various environmental conditions?  The big question is can we make predictions about the potential for field failures similar to how we estimate disease risk with the disease forecasting models.

Alex Wong (a new PhD student) will be looking at how fungicide resistance persists and transfers through a population. We need to understand this because resistance to other fungicides will develop, and we will need to know how to manage these resistant populations while they are still in the minority.

Since you might be wondering, here is the results of our 2018 survey for QoI (G143A) resistance. These data are thanks to funding from the Oregon Wine Board, American Vineyard Foundation, and Washington State Wine Commission. It is also a product of numerous folks in each region taking the time to send in samples.  If you would like to send sample, please contact us walt.mahaffee@ars.usda.gov and we will send you kits and instructions.

Figure 1.  Sample frequency categorized as containing only grape powdery mildew with wild-type genotype
(QoI sensitive – green), the G143A mutation for resistance (QoI Resistant – red), sample having both wild-type and
resistant genotypes (yellow) and no GPM detected (purple) in the sample.  Several Oregon vineyards are scouted
on a bi-weekly basis with extensive swab sampling leading to numerous no detection of mildew – that is good news
– since no mildew was found with the early scouting either.