By: Denise M. Gardner
The Pennsylvania Wine Marketing and Research Board (PA WMRB) annually awards researchers and graduate students grants to explore pertinent topics to the Pennsylvania wine industry. For the 2016 – 2017 fiscal year, four projects were awarded industry-funded grants. Results from these four projects will be presented at the 2017 Symposium, co-hosted by the PA WMRB, Penn State Extension, and the Pennsylvania Winery Association (PWA).
Registration is being organized through the PWA, and can be found here:
This year’s Symposium, held on Wednesday, March 29th at the Nittany Lion Inn (University Park, PA) will only run in the morning and is packed with 5 sessions of information pertinent to both the enology and viticulture fields in Pennsylvania. At the close of the Symposium a lunch will be provided for all attendees.
Guest Speaker has Enology and Tannin Focus
The WMRB Symposium key guest speaker is Dr. Catherine Peyrot des Gachons, Winemaker Consultant at Chouette Collective. Dr. Peyrot des Gachons has assisted Pennsylvania wineries with enhancing their quality production for several years. She will be speaking towards her tannin and wine aroma matrix research that she has been working on at the Viticulture and Enology Department through the University of Montpellier (France).
Tannins: Modulation of wine structure and aroma
From environmental factors on tannin biosynthesis to human interventions to modulate tannin content in wine what do we know and what can we do to modulate wine structure. Can this tannin content impact wine aroma? The presentation will focus on few main points of interest with practical applications.
An additional enology-based presentation will feature Laurel Vernarelli, a graduate student in Dr. Ryan Elias’s lab within the Penn State Department of Food Science. Laurel’s presentation will be an extension from Dr. Gal Kreitman’s work that was presented last year on predicting reductive off-odors in wines. Laurel will explore the use of copper fining in wine production and the potential impact it may have on wine quality. Given the prevalence of reductive off-odors, including hydrogen sulfide, and heavy reliance on copper fining, this topic should be of considerable interest to most wineries.
Reconsidering copper fining in wine
This presentation will include a brief overview of copper fining, along with the impact of reductive thiols and recent findings describing the effect that copper has in wine. A method for using immobilized copper materials in place of copper fining is described. Depending on the result obtained, winemakers can make informed decisions for use of alternative fining techniques when dealing with reductive issues.
For those with an interest in viticulture, this year’s program promises to deliver some key updates. Bryan Hed, Research Technologist for the Department of Plant Pathology, will present his annual updates regarding disease management for Pennsylvania vineyards. For those that are frequent blog followers, Bryan is a lead contributor to the important seasonal reviews. These tend to be very popular posts for growers and his presentations are always informative and practical. If you missed the 2016 seasonal reviews, you can find them here:
- Looking back at the 2016 season
- Late summer/early fall disease control, 2016
- 2016 Post-bloom disease management review
- 2016 Pre-bloom disease management review
Bryan’s talk at this year’s Symposium is a continued study with results collected over 2 years, which helps initiate trends and suggestions useful towards growers.
Updates on Grape Disease Management Research
Fruit zone leaf removal can be a very beneficial practice in the management of harvest season bunch rot. Bryan will start his presentation by briefly reviewing the pros and cons of different timings of this practice. In addition, leaf removal by hand is very expensive and labor intensive, and with the increasing scarcity and rising cost of hand labor, mechanization is crucial to increasing cost effectiveness and adoption of this practice, no matter what the timing. Bryan will follow up with an in depth discussion of the progress made toward mechanizing an early, pre-bloom leaf removal and comparing its effectiveness over a variety of wine grape cultivars and training systems during the past two seasons.
Maria Smith, Ph.D. candidate in Dr. Michela Centinari’s lab, will discuss her research regarding early leaf removal in Gruner Veltliner vines. Maria and Dr. Centinari have previously written a blog post pertaining to leaf removal strategies for Mid-Atlantic vineyards, which could act as an excellent primer to Maria’s presentation in March. Her presentation will deliver two-years (2015, 2016) of data regarding the effects of early leaf removal and cluster thinning techniques on Gruner Veltliner vines.
Vine response and management costs of early leaf removal for yield regulation in V. vinifera L. Gruner Veltliner
Early leaf removal (ELR) and cluster thinning (CT) were applied and compared for yield regulation in Grüner Veltliner over the 2015 and 2016 growing seasons. Early leaf removal was performed at two different times, trace-bloom and fruit-set. We compared the effects of ELR and CT on grape quality, vine health, and economic costs to un-thinned vines.
Finally, Dr. Michela Centinari will follow up with further results regarding sprayable products to reduce frost damage in wine grape vineyards. Michela’s frost research has been a prominent topic at previous Symposiums, and is often featured here on the blog site. While the updated results that will be presented at the 2017 Symposium have not yet been reported through Penn State Extension, please see some of her past blog posts pertaining to frost control and freeze damage in the vineyard:
- Understanding and Preventing Spring Frost/Freeze Damage – Spring 2016 Updates | Wine & Grapes U.
- Updates on Freeze Injury in Grapevines
- Evaluate cost-effective methods to decrease crop losses due to frost injury
- An update to studies on frost injury, by Maria Smith
Spray-on materials: can they reduce frost damage to grapevines?
Dr. Centinari will present results of studies conducted to test the efficacy of sprayable products as a low-cost frost protection strategy. Two materials Potassium-Dextrose-Lac (KDL) and a seaweed extract of Ascophyllum nodosum, were tested for their cryo-protective activity using a controlled-freezing technique on several grapevine cultivars.
We hope to see you there!
By Michela Centinari
The last month has provided a temperature roller-coaster going from a very, perhaps exceptionally, warm March to a cold beginning of April. Many grape growers are keeping their fingers crossed hoping to escape frost injury. As far as I am aware, no budbreak has been observed for grapevines grown in central Pennsylvania, but budbreak may be close in other PA locations. It looks like a good time of year to review some basic concepts related to post-budbreak freeze injury and frost protection options available for grape growers.
Freeze and Frost
We often use the terms “frost” and “freeze” interchangeably to describe a meteorological event, specifically related to air temperature dropping below 32°F (0 °C). However, “frost” and “freeze” definitions reported in the literature are variable and sometimes confusing. I personally like the definitions used in the book: Frost protection: Fundamentals, practice, and economics [Food and Agriculture Organization of the United Nations (FAO), 2005; 1]. In this book frost is defined as “the occurrence of an air temperature of 0 °C or lower, measured at a height of between 1.25 (49.2 in) and 2.0 m (78.7 in) above soil level, inside an appropriate weather shelter”, while freeze “occurs when water within the plant freezes”.
In other words a frost becomes a freeze event if ice forms within the plant tissues.
Keep in mind that:
- It is the ice formation inside the plant tissue rather than low temperatures per se that cause the damage. The formation of ice crystals can be either inter-cellular (space between cells) or intra-cellular (within the protoplasm of cells), the latest causing cell death  (Figure 1). The general hypothesis is that during spring frosts, freeze injury is mainly caused by inter-cellular rather than intra-cellular ice formation [1, 2]. The formation of inter-cellular ice crystals produces a water vapor deficit/gradient between the interior and the exterior of the cells. As a result, water migrates from the inside to the outside of the cells and deposits on the ice crystals formed in the inter-cellular spaces. If ice continues to grow, the cells become more desiccated and lose their turgor . Freezing-induced dehydration can also permanently damage the structure of cell membranes and other cellular components. This usually causes a flaccidity and/or discoloration of the damaged tissue . Thus, the current view is that dehydration injury is the main cause of frost damage. .
- Water within plants doesn’t always freeze during a frost event. Plants have developed avoidance strategies to avoid ice formation in the tissues, for example, by supercooling, and tolerance strategies (e.g., solute content of the cells) to survive inter-cellular ice formation without irreversible damage of the plant tissue .
The critical temperature is defined as “the temperature at which tissues (cells) will be killed and determines the cold hardiness levels of the plant” . Many factors affect the temperature at which damage occurs including: type of plant tissue, stage of phenological development of the bud/shoot, dew point and surface moisture, probability of an ice nucleation event and pre-frost environmental conditions .
Why budbreak is considered the onset of the most susceptible period for cold injury?
Growing organs have a high water content, which makes them susceptible to the formation of ice at freezing temperatures. Air temperature of –2, –3°C can permanently damage green tissues . Early spring growth is particularly susceptible to freeze injury. Freezing tolerance remains low during the most of the growing season and gradually increases late summer and fall (cold acclimation) and reaches its maximum peak in midwinter . In midwinter grapevines are able to tolerate freezing temperature through a complex process called deep supercooling. For example, the cells within the dormant bud become resistant to lower temperature through dehydration (i.e., movement of water to inter-cellular spaces) and accumulation of so-called cryoprotectant (e.g., soluble sugars and proteins). Those compounds lower the freezing point of the water within the plant tissue and stabilize cell membranes  making the dormant buds able to survive temperatures well below freezing. Also, during the dormant season buds are thought to be disconnected or weakly connected to the vine’s vascular tissues, which limit their potential to take up water .
There are two main types of frosts
Advective frost: an advective frost is usually a regional weather event. It occurs when strong, cold winds (colder than the critical temperature) blow into a region day and/or night. The rapid, cold air movement “steals away the heat in the plant causing freeze damage” . Unfortunately there is very little which can be done to protect against an advective frost. For example, wind machines are useless during an advective frost event.
Radiation or radiative frost: A radiation frost is the most common type of frost for many grape growing regions. Luckily, a radiation frost is also the easiest to protect against during a frost event. It occurs when a dry, cold air mass moves into an area when there is almost no cloud cover and no wind at night. Because plants and soil are warmer than the sky temperatures they will “radiate” heat back to their surrounding space and become progressively colder than the air .
Radiative and advective frosts may occur simultaneously, the classification depends on which is one is dominant (Table 1).What are the options available to protect your vines from freeze injury?
Passive or indirect methods (risk minimization)
Passive methods are avoidance strategies, efforts to reduce the probability and risk of freeze damage.
- Site selection
You have probably already heard this, but it cannot be said too many times: “The best time to protect your vineyard from frost injury is before it is planted” . Cold air flows downhill so mid-slope locations are warmer if there are no obstacles to cold air flow  (Figure2). Thus, when evaluating potential sites for establishing your vineyard, look for a site with good air drainage. Get historic records of low temperatures, number of frost-free days, and accurate information on percent slope, aspect or exposure and elevation. You can contact your local county Cooperative Extension office for information about site suitability for a vineyard, or utilize these resources here: http://bit.ly/VydSelectionTools.
- Cultivar selection
Grapevine cultivars may vary in the average day of budbreak by up to two weeks . To avoid or reduce the risk of freeze injury plant cultivars with early budbreak in the location within the vineyard with the lowest risk of frost.
- Training system choice
Many factors related to fruit quality and economics influence the choice of a training system. With regard to risk of freeze damage, a training system which places the buds high on the trellis may reduce frost hazard (Figure 3). Frost hazard is reduced by up to 0.36 °C each 10 cm (3.94 in) above the soil level .
- Pruning choices
- Delay pruning: Pruning too early may accelerate budbreak. Thus, prune as late as possible in frost prone areas of your vineyard.
- Double pruning: this is another option to delay budbreak for cordon-trained vines. The first step is to prune the canes to long spurs, 5 to 8 buds long . Buds at the end of the canes will open first and suppress the growth of basal buds (Figure 3). After frost risk has passed, do a second and final pruning to cut back the long spurs to two-bud spurs. Likewise, for cane-pruned vines one option is to leave long canes (first step) and cut them back (second step) to the desired bud number later, after the frost risk has passed. Some growers opt to retain extra canes as an insurance measure and then remove them later.
- Delaying budbreak by chemical means
Application of vegetable-based oils (e.g., Amigo oil) at nontoxic rates can slow bud de-acclimation and delay grapevine budbreak anywhere from 2 to 20 days depending on several factors including variety, number of applications and coverage [10,11]. Those oils are called “dormant oils” because they need to be applied when the buds are dormant. If you are interested in trying Amigo oil or a similar type of oil in your vineyard, begin with a small selection of vines. Be sure to record phenology, crop yields, fruit composition (Brix, pH, TA) and quality (fruit aromas and flavors, etc.) data for un-sprayed and sprayed vines. In this way, you can assess the impact of oil application on delaying budbreak as well as potential secondary effects on production and fruit quality parameters.
- Middle-row management
Mowing ground cover short will increase the warming of soil during the day and release slightly more heat during the night . Tall cover crops and weeds may also hinder cold air drainage.
Active or direct frost protection methods (frost management)
Active or direct frost protection strategies are efforts to modify microclimate conditions in the vineyard and increase temperatures above injury levels. Some of the most common active frost protection methods are:
- Wind machines (or fans)
Wind machines are well suited for radiational frosts because they use the inversion of air temperature that develops during this type of frost event. Wind machines pull down warmer air, from above the inversion layer, which may provide from 1 – 3°F of warming . The minimum size vineyard recommended for a wind machine is around 7-10 acres. Wind machines may become profitable on sites where there is a 20% (1 in 5 years) or higher probability of spring frost damaging events . It is worth mentioning that wind machines have been noted to produce a loud noise. Operating costs are higher than for over-vine sprinkling systems, but considerably lower than use of return-stack oil heaters and standard propane heaters .
- Over-vine irrigation
Over-vine sprinkler systems have been successfully used for frost protection since the 1940s . Sprinklers provide a constant amount of water covering the buds and shoots. As water freezes it releases a small amount of heat, which increases the temperature of the plant tissue. The level of protection is proportional to the amount of water applied . If properly used, this method is very effective in protecting grapevines from freeze injury. It is the only active method that doesn’t rely on inversion strength during a frost event . However, on the other hand, keep in mind that it requires substantial water resources, is labor intensive and if the system fails during the night/frost event it can cause more damage than otherwise applying no frost protecting strategy.
Heating the vineyard for frost protection is a very old practice. In ancient Rome (at least 2000 years ago) growers used to burn piles of pruned wood and other waste to heat their vineyard during spring frost events . Fossil-fueled heaters are rarely used these days because of the high cost of fuel and labor, low heating efficiency and contribution to air pollution.
Unfortunately there is not a perfect strategy which can provide complete frost protection in every situation. Quite often the combination of different methods is the best option.
If you are looking for detailed information about active frost protections strategies please check:
Understanding and Preventing Freeze Damage in Vineyards. 2007. Workshop Proceedings. University of Missouri Extension.
Evans, R.G. 2000. The art of protecting grapevines from low temperature injury. Proc. ASEV 50th Anniversary Annu. Mtg., Seattle WA, 19–23 June. p. 60–72.
Poling, E.B. 2008. Spring cold injury to winegrapes and protection strategies and methods. Hortscience 43: 1652–1662.
- Food and Agriculture Organization of the United Nations. 2005. Frost protection: Fundamentals, practice and economics. Vol. 1.
- Wilson, S. 2001. Frost management in cool climate vineyards. Final report to grape and wine research & development corporation. Available at: http://www.gwrdc.com.au/wp-content/uploads/2012/09/UT-99-1.pdf
- Poling, E.B. 2008. Spring cold injury to winegrapes and protection strategies and methods. Hortscience 43: 1652–
- Rodrigo, J. 2000. Spring frosts in deciduous fruit trees—Morphological damage and flower hardiness. Scientia Hort. 85:155–173.
- Evans, R.G. 2000. The art of protecting grapevines from low temperature injury. Proc. ASEV 50th Anniversary Annu. Mtg., Seattle WA, 19–23 June. p. 60–72.
- Keller, M. 2010. The Science of Grapevines: Anatomy and Physiology. Publisher: Academic Press.
- Martinson, T. 2001. How Grapevine Buds Gain and Lose Cold-hardiness. Appellation Cornell, Issue 5. Cornell University Cooperative Extension. Available at: https://grapesandwine.cals.cornell.edu/newsletters/appellation-cornell/2011-newsletters/issue-5/how-grapevine-buds-gain-and-lose-cold
- Hellman, E. 2015. Frost Injury, Frost Avoidance, and Frost Protection in the Vineyard. org Available at: http://articles.extension.org/pages/31768/frost-injury-frost-avoidance-and-frost-protection-in-the-vineyard
- Trought, M.C.T., Howell, G.S., and Cherry, N. 1999. Practical considerations for reducing frost damage in vineyards. Report to New Zealand winegrowers. Available at: http://www.nzwine.com/assets/sm/upload/eb/fl/ot/sp/frost_review.pdf
- Dami, I., and Beam B. 2004. Response of grapevines to soybean oil application. Amer. J. Enol. Vitic. 55: 269–
- Loseke, B.J., Read, P.E., and Blankenship E.E. 2015. Preventing spring freeze injury on grapevines using multiple applications of Amigo Oil and naphthaleneacetic acid. Scientia Hort. 193: 294–300.
- Wolf, T.K. 2015. Viticulture Notes. Virginia Tech University Cooperative Extension. April 2016.
By Michela Centinari
It seems like yesterday we were looking at the weather forecast and worrying about cold winter temperature events and the potential for grapevine injury. Now that it is finally starting to get warmer here in Pennsylvania, we may be faced with another threat: spring frost. A grape grower is never bored!
It was another cold winter in Pennsylvania, particularly harsh in the Lake Erie region (Figure 1). At the Penn State Lake Erie Regional Grape Research and Extension Center (LERGREC) temperatures bottomed out at about -21 °F (-30 °C) on February 16, 2015. Unfortunately several cold events (-13, -14 and -15°F) were recorded over the following ten days. On a ‘positive’ note, the week before these extreme cold events, temperatures were lower than normal, with daytime temperature highs well below freezing, except for one day (34°F). These temperatures may have provided a positive, reinforcing maintenance of the vines’ mid-winter cold hardiness . Bryan Hed and the LERGREC’s crew have been checking the extent of bud and trunk damage on Concord and other hybrid varieties.
Information available on cold winter injury on grapevine
At the 2015 Mid-Atlantic Fruit and Vegetable Convention I reviewed the factors that can affect grapevine cold hardiness, explained how to assess bud, cane and trunk cold damage, as well as how to manage cold-injured vines. For information on grapevine cold injury you can refer to the Grapevine cold injury, end of the season considerations blog post and references within.
If you are looking for specific information on winter injury to vine phloem you can check this recent and comprehensive review: Viticulture and Enology Extension News, spring 2015, Washington State University written by Michelle Moyer (Assistant Professor and Viticulture Extension Specialist at Washington State University).
Percentage of winter injury does not equal percentage of crop loss
In March, I attended The Northern Grapes Project Symposium in Syracuse, NY. Tim Martinson (Senior Extension Associate at Cornell University) and Imed Dami (Associate Professor and Viticulture Extension Specialist at Ohio State University) highlighted that the percentage of bud cold damage does not always equal percentage of crop loss. The answer often lies in the pruning adjustment strategies adopted by growers. Dami reported that, despite 40% of bud winter damage, Marquette produced about 5 tons/acre in Ohio last year. Those vines were pruned to 5 bud-spurs (‘hedge pruning’) to compensate for winter injury . .
Tim Martinson reported that last year many growers in the Finger Lakes region (NY) left more buds to compensate for winter injury experienced during the 2013-2014 winter. The growers left up to five-fold more buds than they would have done in a normal year. Many cane-pruned VSP vineyards were spurred to 5-6 bud spurs. It was a pleasant surprise that in 2014 widely planted V. vinifera varieties such as Riesling, Chardonnay, and Cabernet franc, came through better than was expected based on bud mortality estimates. I know that many growers prefer cane pruning, and I understand the reasoning behind that, but please take into consideration that cane pruning is not recommended following winter injury .
How to train suckers of cold injured vines?
Imed Dami recommends that growers “actively” train vines back to their original training system in the same season in order to resume production quicker. Therefore, instead of training suckers vertically (they can become extremely vigorous!) they should be trained horizontally along the fruiting wire. With extremely vigorous vines, four shoots should be selected and then two can be laid horizontally on the fruiting wire. With less vigor, two shoots can be selected and laid horizontally, one to each side. Then, shoots should be tipped to stimulate lateral shoot growth. Lateral shoots growing vertically and upward will become the future spurs next season . Latent buds on the lateral shoots will develop like buds from primary shoots. As long as they are exposed to sunlight and clean from disease and insects, they should have the same cold hardiness as any other buds.
Here is a valuable video regarding pruning with regards to cold injured vines: https://www.youtube.com/watch?v=r1Yhv8Rw38o
A few words on spring frost
As we get close to bud-break, the threat of spring frost is approaching. In the spring of 2014, no frost damage was recoded in grapevines in Pennsylvania and hopefully we will have another frost-free spring. If you would like to get information about frost protection strategies you can check the following websites and newsletters. Unfortunately, there is no new exciting or infallible frost protection method. Site selection remains the best way to protect vines from frost injury.
- Frost Injury, Frost Avoidance, and Frost Protection in the Vineyard, eXtension website, by Ed Hellman, Texas AgriLife Extension
- The ABCs of Frost Management by Robert Evans, Supervisory Agricultural Engineer with the USDA-ARS (retired)
- Viticulture Notes Vol.30, April 2015 by Tony Wolf, Professor and Viticulture Extension Specialist at Virginia Tech University
- Comprehensive presentations on active and passive frost protection strategies can be found at the University of California, Davis Cooperative Extension website
To the often asked question: If my vine gets frosted, should I remove the injured shoots?
The answer is: “There’s not much of a point,” according to Tony Wolf, Professor and Viticulture Extension Specialist at Virginia Tech University. A detailed explanation on how to handle damaged shoots and potential consequences on yield production can be found at Viticulture Notes, Vol.25, May-June 2010
Testing the cryo-protectant properties of KDL
KDL (potassium dextrose lactose; Agro-K corporation, Minneapolis, MN, USA) is a potassium based fertilizer. According to the manufacturer’s literature, spraying KDL shortly before a frost event (24-48 hours) would increase the potassium and sugar levels within the plant and reduce the frost injury on young vine tissue. Although attractive to growers, there is not scientific literature that supports the effectiveness of this product in preventing/reducing frost damage. Numerous grower testimonials are available, but growers usually do not leave an ‘untreated’ control area where the material is not applied, which is critical in order to evaluate the efficacy of KDL as cryo-protectant.
A large scale study coordinated by Tim Martinson (Cornell University) and in collaboration with the Agro-K company (KDL manufacturer) has been set up this spring to evaluate the effect of KDL at several vineyard sites located in NY and PA. Penn State is a collaborating university that is helping to work with six commercial growers that agreed to participate in the study in addition to the Penn State LERGREC in North East, PA.
Although, I’m hopeful there will not be a spring frost that growers have to deal with, if we do end up with a spring frost during the 2015 growing season, this study will hopefully provide some useful recommendations for grape growers.
- Wolf T.K., 2015. Viticulture Notes. Vol. 30 supplement, 17 February 2015
- Dami, I.E. , Ennahli S., Zhang Y. (2012). Assessment of winter injury in grape cultivars and pruning strategies following a freezing stress event. American Journal of Enology and Viticulture, 63: 106-111.
- Dami, I.E. 2009. Ohio Grape-Wine Electronic Newsletter Vol.3: 2-5, 6 Feb 2009.
- Dami I.E., 2014.Ohio Grape-Wine Electronic Newsletter, Vol.25, 3 July 2014.
By: Maria Smith
Since I arrived in August, we have been busy at work continuing to collect field data on our current studies. In addition, we have been developing a new study which takes an in-depth look at the role of canopy management practices have on vine cold hardiness.
After weeks of intense anticipation, monitoring berry development, and fretting over weather, harvest has finally come for us at the Centinari lab. As of last week, our commercial plots with Lemberger, Riesling, Noiret, and Traminette used to study frost tolerance and avoidance have all been harvested (Fig 1, See: “Evaluate cost-effective methods to decrease crop losses due to frost injury”). If you recall, these plots were sprayed with KDL, a commercially available cryo-protectant, and Amigo oil, a product used to delay bud break.
Our preliminary observations show that the Amigo oil treatments had noticeably lower yield in both Lemberger (Fig 2) and Riesling (data not shown) grapes harvested. Despite the lack of frost this spring, we did see a 2 week delay in bud break in Lemberger and a 1 week delay in Riesling with Amigo oil treatments. We are currently checking to see if these differences can be attributed to factors such as the number of shoots per vine between the treatments and/or cluster weight. However, if Amigo oil is in fact the cause of a decrease in yield we should see similar results over multiple years. In the case that Amigo oil has an actual affect on yield, it would be prudent to perform an economic analysis to decide if the use of Amigo oil as a frost avoidance mechanism is worth the cost in decreased yield.
Winemaking is a crucial component in determining what sort of impacts delaying bud break can have on the final product. Thanks to the help of Denise Gardner and a group of students in a winemaking and enology independent study class, we have had the opportunity to crush, press, and ferment our harvested research grapes into wine (Fig 3).
In the initial juice, we have noticed an increase in Brix and TA between the Amigo oil and control treatments in Lemberger, though the Brix of all treatments in Riesling were similar (Table 1). We will be running additional detailed chemical analyses on frozen berry samples taken throughout ripening in the upcoming months.
Future work planned for analyzing the effects of Amigo Oil and KDL include:
- Grape Brix, TA, pH on samples from veraison through ripening
- Wine chemistry – Alcohol, SO2, and color density
- Sensory attributes of wine
- Prepare for year 2 KDL and Amigo Oil application
Winter 2014: New work on canopy management and cold hardiness:
We have recently begun work on a second study in cold hardiness. Canopy management practices are often used to improve the microclimate of grapes within the fruiting zone by exposing clusters to increased light and airflow. Early leaf removal (ELR) has been shown to successfully reduce cluster compactness in tight-clustering varieties, thus reducing incidents of bunch rot (Hed et al., 2014). Another common canopy management practice, cluster thinning (CT), is used to reduce fruit load of overcropping varieties to improve grape and wine quality. However, these practices may also change carbon source-sink relationships with cluster thinning removing carbon sinks and ELR removing photsynthetically active leaves (source), which could potentially alter cold acclimation and hardiness in the vine. Using ‘Chancellor’ vines under 3 imposed canopy management treatments – low-intensity leaf removal, high-intensity leaf removal, and CT – and an un-treated control at the Lake Erie Regional Grape Research and Extension Center, we plan to:
- Quantify non-structural starches and sugars associated with bud cold hardiness between Nov. 2014 and March 2015
- Assess how canopy management practices affect grape and wine chemistry and wine sensory perception
- Perform an economic analysis on the cost and return of canopy management practice implementation
Head B, Ngugi HK, Travis JW (in press). Short- and long-term effects of leaf removal and gibberellin on Chardonnay grapes in the Lake Erie Region of Pennsylvania. American Journal of Enology and Viticulture. doi: 10.5344/ajev.2014.14034
The investigation of grapevine frost treatments is made possible by the John H. and Timothy R. Crouch Program Support Endowment, an endowment founded and funded by the Crouch brothers, original owners of Allegro Winery in Brogue, PA. Additional financial support is contributed by the Pennsylvania Wine Marketing & Research Board (PA WMRB). It is with great appreciation to investigate these projects based on funds and interest provided by the Pennsylvania wine community.
A big thanks to Don Smith for his technical support in our lab and Denise Gardner for her assistance in winemaking. Also, thanks to our wine grape grower collaborators. _________________________________________________________________________________________________
Maria Smith is a viticulture PhD student with Michela Centinari, specializing in cold stress physiology of wine grapes.
By: Michela Centinari
To get ready for my first growing season as a research viticulturist at Penn State University, I met several times with Mark Chien and Denise Gardner and read through all of Mark’s newsletters from the last couple of years. In the past few months I also visited several wine grape growers across the State with the objective of understanding the challenges that the PA wine grape industry is facing. By talking with Mark, Denise and growers, I established that crop yield loss related to late spring freeze injury is one of the economic challenges to the continued growth and advancement of the PA wine grape industry. It was a big relief for many growers that the 2014 spring, after a challenging winter, did not contain a (significant) freeze event recorded after grapevine budbreak. However, the cold temperatures that often occur in late spring, at the very cold-sensitive stages of shoot development, can result in severe crop losses and vine injury comparable to a severe midwinter freeze.
Below is a brief explanation of current frost damage/protection research that I have been working on at Penn State.
What can be done to reduce frost damage in vineyards?
“The best time to protect an orchard (or vineyard) against frost is when it is being established” (Humpries W.J., 1914). Selecting a site with good air drainage is extremely important to reduce the risk of freeze/frost damage. However, many vineyards are located in less than ideal sites. Best management practices for vineyards located in frost vulnerable sites include:
- choosing the appropriate training system and variety,
- strategies for delaying budbreak (double or delayed pruning; chemical application),
- leaving additional canes post pruning, and
- mowing the inter-row grass .
The most effective frost protection methods (i.e. wind machines, helicopters, over-tree covers, heaters, and sprinkling irrigation) may require large investments and not every grower can justify the costs involved. To enhance the profitability of growing grapes in PA the development of frost protection strategies affordable to many growers is critical.
With this in mind, in collaboration with Ryan Elias and Denise Gardner, I’m currently evaluating the effectiveness of spray-on materials (KDL and soybean oil) on reducing the risk of frost injury. In addition, the effect of these materials on vine performance, juice composition and wine sensory characteristics is being evaluated.
Specifically, we are looking at two potential ways to decrease freeze injury in vine green tissues:
1) Increase freeze tolerance of vine green tissue:
If your vineyard is located in a frost prone area, you’ve probably heard about a foliar potassium fertilizer called KDL (potassium dextrose lactose; Agro-K corporation, Minneapolis, MN, USA). According to the manufacturer’s literature, spraying KDL shortly before a frost event (24-48 hours) would increase the potassium and sugar levels within the plant and reduce the frost injury on young vine tissue. Although attractive to growers, there is not scientific literature that supports the effectiveness of this product in preventing/reducing frost damage. Numerous grower testimonials are available, but growers usually don’t leave an ‘untreated’ control area where the material was not applied, which is critical in order to evaluate the efficacy of KDL as cryo-protectant.
Freeze events are not easy to study; they are unpredictable and often variable across a single site. Therefore, a large scale study was set up in collaboration with Cornell University (Tim Martinson and other extension agents) and the Agro-K company (KDL manufacturer) to evaluate the effect of KDL at 25 vineyard sites located in NY and PA. With regards to PA, 6 commercial growers agreed to participate in the study, in addition to the PSU Lake Erie Grape Research & Extension Center. In the absence of a frost event we were unable to gather any data for the 2014 year but we hope to test the same protocol again next year (2015).
Since, as mentioned, frost events are unpredictable I am also using a temperature control chamber to simulate a frost event. In the spring, KDL was sprayed on several grapevine varieties at the PSU research vineyard established at Rock Spring. After 24, 36, and 48 hours, canes with healthy growing shoots were excised and placed in the frost simulation chamber. Several ‘frost’ runs were conducted and I am now in the process of analyzing the data.
Parallel experiments on vinifera and hybrid grapevine varieties are being conducted by Jason Londo at the USDA-Cornell University.
2) Avoid frost injury by delaying budbreak
Delaying of budbreak is a way to reduce the risk of frost and is used mostly for grapevine varieties that break bud early and are at the highest risk of spring frost injury and subsequent crop losses. Studies conducted in Ohio, reported that application of soybean oils delay grapevine bud deacclimation and budbreak anywhere from 2 to 20 days depending on several factors including variety, timing and coverage. However, since grapevine cultivars respond differently to soybean oil applications, optimal strategies for their use need to be established for grapevine varieties grown under PA environmental conditions. Moreover, the effect of soybean oils on fruit composition and wine quality needs to be evaluated, since oil applications could delay fruit ripening, affect yields, fruit chemistry and wine sensory characteristics.
In March field trails were established at two commercial vineyards in Central PA. A soybean oil-based adjuvant, Amigo (Loveland Industries, Greeley, CO) was applied at a 10% concentration (v/v) to runoff with a backpack sprayer during the dormant season (Figure 1A). Amigo oil was applied on March 7 at vineyard “Site 1” on Traminette and Noiret vines, and on March 27 at vineyard “Site 2” on Riesling and Lemberger vines. Temperature sensors were installed in the fruiting wire of selected vines to continuously monitor air temperature throughout the growing season (Figure 1B and 1C).
In the spring, control vines (not-sprayed) and treated vines (sprayed with oil) were visually evaluated for budbreak. Budbreak was determined as stage five of the Eichorn and Lorenz (1977) scale of grapevine development. The grapevine growth stage is being periodically monitored and recorded to date.
The oil application caused various levels of delay in budbreak. At “Site 2,” budbreak delay of approximately 7 and 14 days was observed in the oil-treated Riesling and Lemberger vines, respectively, compared to the control (Figure 2). Looking at Figure 2 you will see how stage 5 (budbreak) was reached on May 13 for the control Lembeger vines and on May 29 in the oil-treated Lemberger vines. Although reduced, a phenological delay was still present at bloom (stage 23) in the Lemberger and Riesling oil-treated vines.
Pictures of Riesling vines were taken on May 20 (Figure 3) and July 9 (Figure 4). On May 20 the difference between oil-treated and control vines was striking. On July 9: both oil-treated vines and control vines showed fully developed and healthy canopies.
The delay in budbreak was much less pronounced in the Noiret at “Site 1” (figure 5). The delay in budbreak in the oil-treated vines was only of a couple of days. Traminette data have not yet been analyzed.
In agreement with previous work  our data suggests that varieties respond differently to soybean oil application. Varieties such as Noiret may need multiple oil applications in order to increase the delay in budbreak. Moreover, environmental conditions may also in part explain the different results obtained at the two sites. Finally, it is important to remember that multiple years of evaluation are needed in order to gather meaningful results and give growers reliable recommendations
What is left to do for the 2014 research season?
- Measure Brix, pH and TA during grape ripening and at harvest to check if the delay in budbreak may cause an un-even fruit ripening.
- At harvest collect yield data (number and weight of cluster per vine) and make wine from the Riesling and Lemberger control and oil-treated vines. Our final goal is to analyze if the oil application has any effect on wine chemistry and sensory perception.
Thanks to Don Smith for his technical support and help in field data collection.
. Trought et al. (1999). Practical considerations for reducing frost damage in vineyards. Report to New Zealand winegrowers.
. Dami, I. and B. Beam. 2004. Response of grapevines to soybean oil application. Amer. J. Enol. Vitic. 55: 269-275.