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.
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.
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
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:
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
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
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.
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.
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,
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.
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.
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.
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.
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 firstname.lastname@example.org 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.
Dr. R. Paul Schreiner, Research Plant Physiologist, USDA-ARS
Renewed interest in vineyard soil health driven in part by advances in microbiome research provides a rationale for reviewing what we know about the foremost component of the root microbiome in grapevines, the arbuscular mycorrhizal fungi (AMF). While other soil bacteria and fungi play important roles in vineyard health and productivity, AMF are unique because of the broad range of benefits they confer. These benefits include improving nutrient uptake from soil (particularly phosphorus (P) and other less mobile ions), increasing soil carbon storage, maintaining soil aggregate stability, and increasing tolerance to drought and pathogens. In the red hill soils of western Oregon, grapevines cannot obtain enough P to grow beyond a few nodes if AMF are absent. They are an integral component of grape and wine production here, and how we treat our soils and vines influences their abundance and the benefits they can provide. There are a few basic issues for viticulturists to consider in managing AMF to get the most from our below-ground fungal partners. These fall under pre-plant and post-plant considerations.
Pre-plant AMF Management. The key pre-plant issue is whether or not the population of AMF is ample enough to ensure that vine roots are quickly colonized. In most cases the answer to this question is yes. AMF are naturally present in almost all soils worldwide because over 80% of all plant species form this type of mycorrhizal association. However, in modern farming systems certain practices can destroy or greatly reduce AMF in soil. While their use is rare in viticulture, pre-plant soil fumigants (methyl bromide, metam sodium, dichloropropene/chloropicrin, and dimethyl disulfide) typically used to control nematodes and soil-borne fungal diseases can wipe out AMF populations. AMF can also be reduced if host plants are absent for an extended period prior to planting a new crop. This can result from long term fallow periods or from the cultivation of non-host plants. Work in Australia to understand the phenomenon of “long fallow disorder” showed that a fallow period of 1 year or more reduced AMF propagules in soil resulting in poor AMF colonization and P deficiency in subsequently planted crops. Soils from long fallow plots could be rescued by adding AMF back to the system from recently cropped soils. Weeds can also maintain AMF populations in soil and may be important in some cases. For example, my lab showed that soil solarization conducted in the summer reduced AMF populations the following spring in western Oregon because solarization suppressed weeds over the fall and winter that acted as bridge to maintain AMF. Growing cash crops or cover crops that are not hosts for AMF can also reduce AMF propagules in soil. A number of plant species do not form mycorrhizal associations of any type or form other types of mycorrhizas that will not maintain AMF propagules in soil. Common ones used as cash crops or cover crops in agriculture are the mustards (Brassicales) including numerous vegetables, rapeseed, and meadowfoam, as well as spinach, buckwheat, amaranthus, and lupine. A new vineyard planting that follows these crops may benefit from adding AMF at planting or boosting the native AMF population by growing a host plant cover crop before planting. Planting a vineyard after hazelnuts is the most likely scenario where adding AMF will be needed in western Oregon because hazelnuts are ectomycorrhizal and because the orchard floor is kept bare for many years (not allowing host plant weeds or cover crops to maintain AMF).
Exactly when the AMF population is too low for healthy vine establishment is not clear. I conducted numerous AMF inoculation trials when I first began working on grapevines over a decade ago in nurseries and new vineyards. Results from the vineyard trials showed that inoculation with AMF (produced in my lab) enhanced root colonization and improved vine growth in only one of five experiments conducted in the Willamette Valley. By year 2, however, the non-inoculated control vines no longer differed from inoculated ones, and in no case in the nursery or vineyard was vine survival significantly altered by inoculating with AMF. Viable AMF were present at all the sites where we conducted inoculation trials so that the control vines became colonized at every site to at least a small degree.
Post-Plant AMF Management. Even though grapevines rely heavily on AMF to obtain ample P and often other nutrients, they also can reduce the extent of AMF colonization within their roots when nutrient status (particularly P) is high. Therefore, avoiding fertilizer applications unless a nutrient is demonstrated to be low or deficient is a good practice to reduce negative impacts on AMF. For example, AMF colonization of Pinot noir roots was reduced in vineyards receiving foliar P fertilizer sprays. Root colonization was also negatively correlated to leaf P and leaf nitrogen (N) concentrations across a survey of 31 Chardonnay and Pinot noir vineyards in the Willamette Valley. There is evidence from other farming systems that organic forms of nutrients are less harmful to AMF than synthetic fertilizers, but even organic sources including manure can reduce AMF and potentially reduce other benefits they provide if applied at high rates.
Soil applied fungicides will obviously harm AMF, but what about foliar fungicides? At this time, there is no evidence that the fungicides used in our spray programs to control powdery mildew and grey mold have a negative impact on AMF. However, reducing tillage can benefit AMF because tillage breaks up their hyphal networks in soil. Indeed, we showed that in-row cultivation reduced AMF colonization in Oregon vineyards as compared to herbicides (mainly glyphosate) used to suppress in-row weeds. Finally, in separate studies both east and west of the Cascades, AMF colonization in grapevine roots was lower in vines at wetter sites (west) or in vines that received more irrigation water (east). Therefore, applying less water will also enhance AMF in vineyards. Since AMF provide other benefits beyond their key role helping grapevines obtain P, choosing management options that enhance their abundance (or at least do the least harm) also improves other aspects of soil health.
Dr. James Sterns, Associate Professor, Department of Applied Economics, Oregon State University
The 2018 Direct to Consumer Wine Shipping Report, published collaboratively by the information technology company SOVOS and the trade publication Wines & Vines, has just been released and an overriding message within it is clear – Direct to Consumer (DtC) sales are growing rapidly in both volume and value of sales. The reported numbers are eye-catching: total U.S. consumer spending in 2017 on DtC wine shipments of $2.69 billion, with 5.78 million cases shipped. And reading further into the report, there are even more impressive quotes to be found:
“Oregon is clearly having its day. Due to larger than average harvests in 2013-2015, along with increased attention from investors, the trade, media and consumers, Oregon’s sales and shipments are flourishing.”
“Since 2012, the volume of wine shipments from Oregon wineries has increased by 214%, with the value of those shipments increasing by 227%…Oregon kept rolling in 2017, delivering the greatest DtC shipping increase of all six regions tracked.”
“As in past years, the small winery (5,000 to 49,999 cases) and very small winery (1,000 to 4,999 cases) categories drove the DtC shipping channel, accounting for 70% of the value of U.S. winery shipping.”
“By nearly every measure, the winery DtC shipping channel continues to outperform every other retail channel in the United States, be it grocery stores, independent fine wine shops or convenience stores.”
“…tasting rooms and wine club sales still drive the lion’s share of DtC growth…”
With news like that, Oregon wineries are obviously aware of and intent on continuing their efforts to sell more wine directly to the consuming public. But there remains an open question about at least one component of DtC marketing, and it’s a question that I have heard repeatedly in the past 18 months. It’s a sentiment shared by many Oregon winery owners and managers. Simply put, there’s a shared sense that, “we really don’t know that much about how to effectively manage our wine clubs.”
As part of a new OWRI initiative, my colleague Catherine Durham and I are studying how wine clubs throughout the state of Oregon are managed, and more importantly, what are the preferences and motivations of wine club members. This research is progressing through two phases – first, this past Fall we solicited responses to a questionnaire from Oregon wineries about how they manage their wine clubs. These results are in and are helping to inform our next phase of research – sending questionnaires directly to wine club members, asking them about their participation in wine clubs. Our lines of inquiry are focusing on the following: What features and benefits of club membership do they value most? When and why did they join the wine club, and what incentives will motivate them to stay in the club? How many clubs have they participated in, both historically and currently and what has motivated them to change or leave a club?
We know of at least one other recent project that asked similar questions. A study published by researchers at Sonoma State University was based on a small sample of 25 students majoring in wine business, which limits how much we can generalize the findings. And yet their study does help support our efforts, in part by identifying a set of common wine club attributes, which included wine club levels (ranging from one to six), ways to differentiate across wine club levels (most commonly by price points), allowing customized ordering, the number of shipments per year (ranging from one to six), the number of bottles per shipment, price range of bottles shipped, and associated tasting room benefits (such as allowing non-club members accompanying club members in a tasting room complimentary tastings and/or discounts). These are some of the specific topics that we plan to include in our club member questionnaire.
We hope to have the club member survey ready to use within the coming weeks. We will be completely dependent upon the cooperation of Oregon wineries and their wine club managers to distribute this questionnaire. In appreciation of the proprietary nature of club member lists, we are asking that the wineries distribute an email with a link to a web-based questionnaire to all of their club members. Results should be available by late spring.
If you have any questions or thoughts about this research, please contact me at your convenience. My email address is email@example.com and the direct line to my office is 541.737.1406.
Dr. Jay W. Pscheidt, Professor and Extension Plant Pathology Specialist, OSU Dept. of Botany and Plant Pathology
Dr. Patty Skinkis, Associate Professor, Viticulture Extension Specialist, OSU Dept. of Horticulture
As we get into fall with a little rain, we wanted to highlight the potential for various bunch rots. These bunch rots are weather-, disease- and insect-related. Botrytis bunch rot and sour rot are the two most frequently encountered in this region, but others that are important around the world are not common here.
Botrytis Bunch Rot We in Extension have written about the ubiquitous Botrytis bunch rot off and on over the years. Water in the form of rain or irrigation drives this disease, especially at bloom and near harvest. The fungus can infect (gain entrance to) ovaries and colonize floral tissue at bloom. It then becomes inactive (quiescent) and does not reactivate until berries begin to ripen in the fall. Open training systems and cluster zone leaf removal help create an environment that does not favor the disease. Fungicides are less effective than canopy management but are useful in wet years. Fungicide use can be challenging since sprays need to go on well before you know whether it will be a wet season, and fungicide resistance is common and complicated by fungicides used in your powdery mildew program. Read more about Botrytis bunch rot here:
Powdery Mildew Powdery mildew is not really a bunch rot. Depending on how early infection occurs, the result may be poor fruit set or small and split berries. By the time véraison rolls around there is not much of a cluster to rot. Small or light infections of the berry, however, can also allow Botrytis to get a foothold. Good powdery mildew control will aid Botrytis bunch rot control.
Sour Rot New research out of New York has defined sour rot and given us clues as to how to manage it in the vineyard. Very specifically, sour rot occurs when the berry becomes brown AND has both ethanol and acetic acid accumulation, which gives it the characteristic sour vinegar smell. The ethanol is no surprise as it comes from yeasts, but the acetic acid comes from bacteria. There is a sequence of events that is required for sour rot to occur, and it starts with wounding.
Somehow the berry skin breaks, allowing entry of these organisms. This can happen through berry growth, rainy weather during ripening (as we had a few years ago) and/or insect or bird damage. The yeasts produce ethanol that is then converted to acetic acid by the bacteria. This is still not enough to get sour rot symptoms. In New York, fruit flies were critical for sour rot symptom development. They do not need to introduce the microorganisms but are a factor all in themselves, and that factor is unknown at this time. It is unknown whether other insects, such as yellow jackets, can also induce symptoms. Targeting fruit flies with insecticides in the vineyard did result in less sour rot development. Interestingly, targeting the microbes with anti-microbial sprays alone was not effective. You can learn more by reading:
Other Grape Rots A few other grape rots have been reported or observed in the PNW. Several more have been described in other viticultural regions of the world, including the following list. (We mention these various rots because it is always possible for new exotic organisms to be introduced into our region. They may just be a temporary “flash in the pan” problem or could establish as an annual concern over time)
Phomopsis: I have seen Phomopsis fruit rot only once in my 30 years here in Oregon and that was in an unmanaged vineyard used for nursery stock. A disease with similar symptoms from the southeastern USA is called bitter rot. The only way to tell the difference is by taste, which I had enough of during my postdoctoral research in New York!
Black rot has been reported from eastern Washington on Concord grapes but is not a common problem.
Anthracnose (or better named “bird’s eye rot”) and ripe rot are also fungal fruit rots more commonly found in the southeast USA.
White rot is a real fungal disease of grape and not someone just joking around about bird doodoo on a leaf!
Downy mildew: This is not a problem here but is common in many other regions of the world.
In the Winery Grapes affected by fruit rot diseases can cause problems in the cellar as well. Dr. James Osborne wrote this article titled, Dealing with Compromised Fruit in the Winery, for Wines & Vines magazine in August, 2014.
Bottom Line It is most important to manage powdery mildew and Botrytis bunch rot, and to scout for fruit flies around harvest. Also, keep an eye out for unusual problems or rots. If you find some suspect diseases or unusual rots, contact your local Extension team member. We hope that the harvest will go smoothly with few problems.