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Understanding and Preventing Spring Frost/Freeze Damage – Spring 2016 Updates

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 freezeoccurs 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 [1] (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 [3]. 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 [4]. Thus, the current view is that dehydration injury is the main cause of frost damage. [2].
Figure 1. Ice formation in the extra-cellular space. Source: http://ilc.royalsaskmuseum.ca/ilc1/pages/12c/13f/pf13fp2p1.htm

Figure 1. Ice formation in the extra-cellular space. Source: http://ilc.royalsaskmuseum.ca/ilc1/pages/12c/13f/pf13fp2p1.htm

  • 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 [1].

Critical temperatures

The critical temperature is defined as “the temperature at which tissues (cells) will be killed and determines the cold hardiness levels of the plant” [5]. 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 [6].

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 [6]. 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 [6]. 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 [6] 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 [7].

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” [5]. 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 [5].

Radiative and advective frosts may occur simultaneously, the classification depends on which is one is dominant (Table 1).

Table 1. Frost event terminology and typical characteristics

Table 1. Frost event terminology and typical characteristics [source FAO, 2005; 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” [5]. Cold air flows downhill so mid-slope locations are warmer if there are no obstacles to cold air flow [8] (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.

Figure 2. Cold air drains downhill and settles in low spots, where frost damage is most likely

Figure 2. Cold air drains downhill and settles in low spots, where frost damage is most likely [source FAO, 2005; 1]

  • Cultivar selection

Grapevine cultivars may vary in the average day of budbreak by up to two weeks [8]. 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 [9].

Figure 3. Comparison of freeze damage in Noiret (Vitis hybrid) shoots after a spring frost event. The vines were trained on (a) top wire cordon (6 ft. from the ground) and (b) vertical shoot position (3 ft. from the ground) (b). The two vines (a and b) are in adjacent, parallel rows.

Figure 3. Comparison of freeze damage in Noiret (Vitis hybrid) shoots after a spring frost event. The vines were trained on (a) top wire cordon (6 ft. from the ground) and (b) vertical shoot position (3 ft. from the ground) (b). The two vines (a and b) are in adjacent, parallel rows.

  • 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 [8]. 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.
Figure 4. Budbreak of apical buds and suppression of basal buds in double-pruning. Source: Ed Hellman, Texas AgriLife Extension [8]

Figure 4. Budbreak of apical buds and suppression of basal buds in double-pruning. Source: Ed Hellman, Texas AgriLife Extension [8]

  • 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 [12].  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 [3]. 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 [3]. 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 [3].

  • Over-vine irrigation

Over-vine sprinkler systems have been successfully used for frost protection since the 1940s [5]. 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 [5].  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 [5]. 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.

Figure 5. Over-vine sprinkler system in use and green tissue ‘wrapped’ in ice. Source: https://www.wineshopathome.com/frost-protection-vineyards-2

Figure 5. Over-vine sprinkler system in use and green tissue ‘wrapped’ in ice. Source: https://www.wineshopathome.com/frost-protection-vineyards-2

  • Heaters

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 [5]. 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.

 

Literature cited

  1. Food and Agriculture Organization of the United Nations. 2005. Frost protection: Fundamentals, practice and economics. Vol. 1.
  2. 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
  3. Poling, E.B. 2008. Spring cold injury to winegrapes and protection strategies and methods. Hortscience 43: 1652–
  4. Rodrigo, J. 2000. Spring frosts in deciduous fruit trees—Morphological damage and flower hardiness. Scientia Hort. 85:155–173.
  5. 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.
  6. Keller, M. 2010. The Science of Grapevines: Anatomy and Physiology. Publisher: Academic Press.
  7. 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
  8. 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
  9. 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
  10. Dami, I., and Beam B. 2004. Response of grapevines to soybean oil application. Amer. J. Enol. Vitic. 55: 269–
  11. 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.
  12. Wolf, T.K. 2015. Viticulture Notes. Virginia Tech University Cooperative Extension. April 2016.

 

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Winter notes: What is going on in your vineyard right now?

By Michela Centinari

This past November and December were surprisingly warm months in Pennsylvania with temperatures rising into the 60s and even 70s °F (Figure 1a, b). In January temperatures dropped to single digits in many eastern U.S. regions [1] followed by a virtual temperature rollercoaster ride in the next months (Figure 1).  On a positive note, viticulture specialists from Virginia Tech (T. Wolf and T. Hatch) did not observe any winter injury in Cabernet Sauvignon and Merlot buds and canes collected on January 8 (northern Virginia) [1].

Figure 1. Daily maximum and minimum temperatures recorded in (A) northeast PA, near Scranton (Lackawanna County) and in (B) south central PA, York Springs (Adams County) during the 2015-2016 fall and winter. Dashed line indicates freezing temperature (32 degrees F).

Figure 1. Daily maximum and minimum temperatures recorded in (A) northeast PA, near Scranton (Lackawanna County) and in (B) south central PA, York Springs (Adams County) during the 2015-2016 fall and winter. Dashed line indicates freezing temperature (32 degrees F).

In many regions of Pennsylvania temperatures in January and February did not reach the critical low threshold (Figure 1B) that tends to injure many of the cultivars grown in PA and we are not currently concerned about winter injury in the majority of the state. However, on February 14 temperatures of -10°F and below were recorded in some areas of the state (report from growers from northeastern PA and Figure 1A).  The lowest temperature in Pennsylvania (-19°F) was recorded in Potter County on February 14 [2].

Although we are not aware of the extent yet, we anticipate winter injury in some of the cultivars grown in those areas.

A few reminders about the cold hardiness process:

In late summer/early fall, cold-tender grapevine tissues produced during the growing season gradually acquire cold hardiness and transition to a cold-hardy stage (known as cold acclimation) as a response to low temperatures and decreasing day length [3] (Figure 2). Bud (and other tissues) cold hardiness reaches its maximum level in mid-winter (known as maximum hardiness). Later in the winter as temperatures increase, the buds begin to lose hardiness (known as deacclimation) [4]. The deacclimation stage ends in budbreak and active growth.

Figure 2. Profile of bud cold hardiness in grapevines.  Figure from Zabadal et al. 2007.

Figure 2. Profile of bud cold hardiness in grapevines. Figure from Zabadal et al. 2007.

It is a well-known fact that bud cold hardiness depends heavily upon the grapevine species and cultivar. For the past two winters (2013-2014; 2014-2015) many growers in the eastern and midwestern U.S. have had the unfortunate opportunity to test this in their own vineyards.  However, in addition to its genotype, the cold hardiness of a specific cultivar is determined by environmental conditions, such as seasonal temperatures and their variation, and by vineyard management practices [3].  It is important to remember that exposure to decreasingly lower temperatures plays a major role in the ability of the vine to acquire its maximum cold hardiness. In other words:

  • The colder the region, the closer a vine gets to its maximum cold hardiness potential [4]. For example, bud cold hardiness of Chardonnay and Riesling in the Finger Lakes region of NY (cooler region) was found to be 2 to 3°F greater than that of the same cultivars grown in Virginia (warmer region) [4] (Figure 3).
Figure 3. Profile of bud cold hardiness of the same grapevine variety in a cold (New York) and a warm (Virginia) region.  Figure from Zabadal et al. 2007.

Figure 3. Profile of bud cold hardiness of the same grapevine variety in a cold (New York) and a warm (Virginia) region. Figure from Zabadal et al. 2007.

  • “The type of winter determines the extent of bud cold hardiness” [5], thus the absolute cold temperature that injures the same cultivar may vary between winters. J. Londo (Geneticist, USDA, Grape Genetics Research Unit, Geneva, NY) reported that the average mid-winter LT50 (lethal temperature for 50% of the buds) for labrusca varied from -24.71 °F in 2012-2013 (defined as a mild-cool winter in upstate NY) to -26.8°F in 2013-2014 (cold winter but with big swings in temperatures) to -26.5°F in 2014-2015 (sustained cold winter) [5]. However, species and cultivars may vary in their response to different temperatures/winters. For example, Tim Martinson, senior viticulture Exten­sion associate at Cornell University, did not observe a decrease in bud hardiness of Riesling vines this year as compared to last year [1].

A few of the things that Penn State Extension recommends to growers:

  • Plan on pruning the hardiest cultivar first and finish with the least hardy [4]. If a cold event occurs late in the winter, like in the middle of February, and cold-sensitive cultivars were not pruned yet, you can still assess bud cold damage and adjust pruning severity accordingly [3]. Leaving extra buds on the vines, and adjusting shoot number after bud break certainly cost growers more money, but it also increases the chance to produce a crop, hopefully close to normal.
  • If your site is an area with moderate to high risk of cold damage events, consider keeping some freeze-tolerant grape cultivars in the mix to reduce the economic downside risk. These are considered cultivars that you can rely upon to “pay the bills.” Cold-hardy cultivars, most of which were released by the breeding program of the University of Minnesota (i.e. Marquette, La Crescent, Frontenac, etc.), are increasing in popularity mostly, but not only, in regions where vinifera or other inter-specific hybrid varieties are not well suited or have struggled to survive and perform well in the long term.

Thanks to The Northern Grapes Project we are gaining a better understanding of how to optimize viticultural, winemaking, business management and marketing practices of these fairly new cold-hardy cultivars. For example, important information on Cost of Production in Cold Hardy Grapes was recently published in the Northern Grapes Project newsletter [3]. The fact that most consumers may still be unfamiliar with those varieties and the wine styles they produce doesn’t necessarily mean that they not will have chance to stand alone as a varietal wine if they produce high quality wines.

  • As Zabadal et al. [4] pointed out Minimizing winter injury is usually not the primary goal of a grape grower; however it must be given attention because of its huge impact on profitability”. Each grower should carefully evaluate if the cost of vine management practices that reduce vine winter injury can increase the business profit.
  • Finally, the most important step, making informed decisions before planting a vineyard and always applying good viticulture practices, which includes keeping the vines healthy and in balance.

Only time will tell what weather conditions the rest of winter and early spring will hold in store for us. However, if your vineyard is located in a frost prone area and you have dealt with spring (post-budbreak) freeze damage in previous years, this would be a good time to review the frost protection practices available and assess if and what options could be used for your specific  situation (see for instance: Frost Protection in Orchards and Vineyards by R. Evans, USDA or Methods of Vineyard Frost Protection by P. Domoto, Iowa State University).

A two-year study was conducted by our research team at Penn State to evaluate “low-cost” frost protection practices for their efficacy to avoid/reduce crop losses due to spring freeze injury. We tested the effect of a vegetable-based oil (Amigo oil) to delay budbreak on two vinifera (Lemberger and Riesling) and two inter-specific hybrid cultivars (Noiret and Traminette). We also tested the impact of KDL (Agro-K’s Potassium Dextrose-Lac®), sprayed shortly (»24 hours) before a frost event, on reducing frost damage to young grapevine shoots. The impacts of Amigo oil and KDL applications on yield components, fruit composition and perceived wine quality were also assessed. Results from this trial will be presented at the 2016 Pennsylvania Wine Marketing and Research meeting: http://bit.ly/PAWMRB2016Symposium.

 

References

  1. Jones McKee L. 2016. Cold hardiness and dormancy, pp58-64. Wines and Vines, March 2016.
  2. Eherts F. 2016. February 2016- Pennsylvania Weather Recap. The Pennsylvania Observer. March 2016.
  3. Martinson, T. 2001. How Grapevine Buds Gain and Lose Cold-hardiness. Appellation Cornell, Issue 5. Available at: https://grapesandwine.cals.cornell.edu/newsletters/appellation-cornell/2011-newsletters/issue-5/how-grapevine-buds-gain-and-lose-cold
  4. Zabadal, TJ, Dami, IE, Goiffinet, MC, Martinson, TE, and Chien, ML. 2007. Winter injury to grapevines and methods of protection. Extension Bulletin E2930. Michigan University Extension.
  5. Londo J. 2015. The Big Chill: bud dormancy and cold hardiness in grape. Northern Grapes webinar, December 8, 2015. Available at: http://northerngrapesproject.org/?page_id=257
  6. Northern Grapes News. 2016. Vol. 5, Issue 1, February 18, 2016. Available at: http://northerngrapesproject.org/?page_id=213

 

Crown Gall – A Growing Concern in Vineyards

By: Bryan Hed, PSU Research Technologist

The past two winters have ramped up concerns about crown gall in Pennsylvania and other parts of the Northeast. Wine grape growers are discovering, many for the first time, the horrors of this disease and the extent of the damage it can cause in their vineyards. While there is reason for great concern, I would like to start out by saying that research efforts are generating extensive information on management of this disease, and there are new solutions from research in the pipeline.

CROWN GALL AND INCREASE SUSCEPTIBILITY TO WINTER INJURY

After the past couple of harsh winters vines have been collapsing in your once “healthy” and productive vineyard. What’s going on?

In some cases, brutal winter cold has simply damaged or killed a vine that was not suitable for its site. It is well known that the many varieties of Vitis vinifera that vintners prefer are simply less cold hardy than many of the French hybrid varieties. The crown gall bacterium, Agrobacterium vitis, can also play a large role by rendering infected vines incapable of properly repairing the cold damage to their trunks. The most obvious symptom of crown gall infection is gall formation at the base of infected vines. These tumor-like growths eventually choke out the vascular connection between roots and canopy, and the vine collapses (Figures 1 and 2).

How did vines get contaminated with the crown gall bacterium in the first place and why is it now causing problems?

There are many sources of the crown gall bacterium and probably many ways in which vines can acquire it. It is now known that the bacterium exists in populations of wild grapevines and can be found on plant surfaces in the vineyard. The most likely or common source, however, is through contaminated nursery stock. Since the bacterium can live systemically as an endophyte inside vines used for propagation material, cuttings from that material will carry the bacterium as well. The bacterium that causes crown gall can probably live inside vines without ever causing any disease, without causing the growth of tumors at the base of the trunk, without bringing about the collapse of vine trunks. Cuttings, produced from symptomless, contaminated mother vines, may be contaminated with the bacterium from “day one,” but may never develop crown gall. This is probably the case in California and other Mediterranean climates where many of the world’s wine grapes are grown.

So why is crown gall such a problem here in the Northeast, and not in California?

The crown gall bacterium shifts from benign coexistence, as an endophyte inside vines, into a tumor-inducing organism when there is damage or injury to grapevine vascular tissue. When injury occurs to the cambium, the bacterium attaches to plant cells at the wound site and literally inserts a copy of a self-replicating DNA strand (called a plasmid) into the plant cells (infection). The plasmid contains genes that code for hormone production that leads to the growth of tumors. These genetically modified grapevine cambium cells begin to grow tumor tissues with poorly organized vascular structure (that is, not capable of adequately conducting resources needed by the vine) at the wound site instead of organized vascular tissues. The injured trunk areas are never properly repaired by functional vascular tissue and as the tumor tissues grow, the trunk becomes more and more non-functional and eventually the vine collapses. And what is the most common cause of widespread grapevine trunk damage in the Northeast? Severe winter cold—which does not occur in most parts of California and similar warm, wine grape production climates.

 

Figures 1 and 2: Crown gall on a trunk of French hybrid ‘Chancellor’ before and after bark is stripped away. Galls appear in spring as white callous tissue, most often at the base of the trunk, gradually turning green/brown and finally dying to turn into dark brown/black corky tissue.

All is not lost—tips on vineyard renovation

A collapsed vine with healthy roots will throw new shoots from the base of the plant, and these can be used to make new trunks and restore the vine to productive status. Here in the “Great White North” of Erie County, we renovate vines almost every year (Figure 3). Vines “laid low” by crown gall are often capable of being completely restored to productive life. Rather than ripping out your 7 or 10-year-old vineyard and replacing it, it can be more cost-effective to train up new trunks with the potential for a partial crop this year and a full crop in Year 2. An exception to this remedy is when trunks of grafted vines were not hilled with soil in the fall and the base of scions experienced the full force of the severe cold. This can completely kill the scion and leave growers with nothing but the rootstock. In this case, growers may have to start over with new vines, unless there is potential for field grafting of new scion wood. Also, when very young or newly planted vines develop crown gall, it is best to remove the plants, and replace them. The bacterium can be found in roots as well as trunks and can survive for long periods of time (years) in the soil, and it is important to remove all parts of infected plants.

Figure 3: Picture from the NE1020 grape variety trial at North East in Erie county PA. Note the six-year-old Gruner veltliner/101-14 vines (foreground) that were laid low by the 2014 Polar Vortex. Although existing canopies are dead or nearly dead, a flush of sucker growth from the scion (protected by hilling during the previous fall) provides the means for trunk renewal. Also note the full canopies of cold hardy French hybrids within the same block. While ALL cultivars of V. vinifera were killed back to the ground, all hybrids went on to produce partial to full crops in that year.

Figure 3: Picture from the NE1020 grape variety trial at North East in Erie county PA. Note the six-year-old Gruner veltliner/101-14 vines (foreground) that were laid low by the 2014 Polar Vortex. Although existing canopies are dead or nearly dead, a flush of sucker growth from the scion (protected by hilling during the previous fall) provides the means for trunk renewal. Also note the full canopies of cold hardy French hybrids within the same block. While ALL cultivars of V. vinifera were killed back to the ground, all hybrids went on to produce partial to full crops in that year.

 

All of us would love to be able to train up one original trunk and rely on that single trunk for every vine, every year. Unfortunately for many in the Northeast, that’s a pipe dream. Now that you know about crown gall in your vineyard, you can assume that more vines are contaminated than you previously thought. For example, we have a Chambourcin vineyard at the North East lab in which just about every vine is host to the crown gall bacterium. I had no idea this was the case until the winter of 2003-2004, when brutal cold caused nearly every vine trunk to explode with crown gall the following spring (Figures 4 and 5). Apparently, nearly every vine was contaminated with the bacterium and the vineyard collapsed! After discussing my conundrum with Dr. Tom Burr at Cornell University, an expert in crown gall biology/pathology, we spent the 2004 season training up new trunks for every vine, using only shoots that originated from below the galls. From 2005 on, the vineyard was enormously productive for almost ten years. Then came the polar vortex of January 2014, followed by the severe winter cold of February 2015, and with it more devastating bouts with crown gall.

Improving your odds that a winter cold event will not lead to complete loss

Growers of V. vinifera in Erie County, PA have pretty much resigned themselves to losses from winter cold and crown gall every few years, and they deal with it in a number of ways. The first way is by growing vines on multiple (2 to 3) trunks. The logic follows that if one or two trunks collapse from crown gall there may still be one trunk that produces a crop and provides some income until new trunks can be groomed to replace the galled/damaged ones. Trunks do not need to be replaced as a matter of regular maintenance, but rather when they become injured and/or diseased. The maintenance of more than one trunk can greatly improve your odds that a winter cold event will not lead to complete loss.

Figure 4 and 5: Collapsed vine of French hybrid ‘Chambourcin’ (left) following winter cold damage to the trunk and onset of crown gall at the base of the trunk (right). The entire vineyard eventually collapsed, but was completely restored with new trunks from shoots (suckers) emanating from below galls.

Figure 4 and 5: Collapsed vine of French hybrid ‘Chambourcin’ (left) following winter cold damage to the trunk and onset of crown gall at the base of the trunk (right). The entire vineyard eventually collapsed, but was completely restored with new trunks from shoots (suckers) emanating from below galls.

Growers of the hardier French hybrids generally suffer fewer economic down times from winter cold-induced crown gall than growers of V. vinifera.  We cannot escape bouts of brutally cold winter weather, but we can (and should) plan for the worst and try to wisely match variety with site in order to minimize or eliminate losses to winter trunk damage and crown gall. Simply put, cultivars of V. vinifera and cold-sensitive hybrids should be planted only on the best sites in Pennsylvania—sites that ensure good cold air drainage during the worst bouts of winter weather. Where a vineyard is already established, vine management that maximizes vine cold hardiness (balanced timely nutrition, effective disease control, proper balance between growth and yield, good weed and water management) is absolutely essential for minimizing trunk damage and the onset of crown gall after a severe winter cold event.

For grafted vines, hilling soil around the graft union in late fall will protect the base of the scion and may ensure that scion bud wood will survive to throw shoots for replacement trunks the following spring. During the following spring, hilled soil should be removed from around the graft to prevent rooting of the scion, which would otherwise defeat the purpose of the rootstock. Although an added expense, this practice is commonplace in many wine growing regions of the Northeast. Farther south and especially in the mid-Atlantic region, many growers have been avoiding this management practice because it represents a substantial added expense, can contribute to erosion on steep sites, and can increase the odds that vines may become mechanically damaged. Unfortunately, severe cold during the past two winters caused heavy damage to the less favorable variety/site combinations even in parts of southern PA and the mid-Atlantic. Where grafts were not protected, the supply of scion buds that would have provided for new trunks was killed. In such cases, all but the rootstock dies and the vine must be replaced—a much more expensive operation than trunk renewal. So in these more southerly regions, the decision to hill or not, may be less clear. In southern PA, proper variety matched to the site along with multiple trunk maintenance may be sufficient for sustainability. However, on poorer sites that suffer more frequently from a severe winter cold event, annual hilling of grafts may be necessary or a grower may need to rethink his/her established variety/site combination. As in all matters of farming, growers must weigh the expense of a practice against the magnitude of the consequences for not doing so as well as the odds that he or she will get hit with another severe cold event. The prudent integration of these management practices will help to guarantee that farms can remain sustainable and profitable in the Northeast.

Research in the pipeline

Once contaminated, there is no practical way to rid a vine of the crown gall bacterium. The best long term solution rests with the production of crown gall-free planting stock so that growers can at least start with a clean vine/clean vineyard. To that end, through funding from the National Clean Plant Network, Dr. Tom Burr’s grape research program and others are devoted to the generation of mother vines free of crown gall that can be used to start clean sources of grapevine nursery material. The emphasis in this effort is the development, and ongoing refinement, of extremely sensitive tests used to detect the presence of the pathogen, in order to determine whether a vine that might be used for propagation is “clean” or contaminated. Clean vine material can then be confidently used to establish grapevine mother blocks that will serve as the foundation of nursery propagation stocks. In turn, the mother blocks and nursery stocks can be continuously monitored for the presence of the bacterium using these same tests. The latest research has indicated that plants free of the crown gall pathogen can be generated but they will need to be assayed periodically to ensure they remain clean. Remember, however, that the crown gall pathogen, once introduced into a vineyard through contaminated plants, can live in the soil for many years. Therefore, the availability of crown gall free planting stock is not going to end our encounters with this pathogen. Clean planting stock will reduce or help to eliminate the incidence of crown gall in new plantings, but the pathogen will likely always remain present and northeastern growers will still have to manage their vineyards with a view toward minimizing the incidence of crown gall.

Extension Support for the Upcoming Season:

  • This blog post and others will continue to be made available at Wine and Grapes U. to assist growers with the latest information. We hope you find this useful for managing crown gall and we encourage feedback.
  • You can sign up for the Penn State Extension V&E News listserv by email Denise Gardner at dxg241@psu.edu.  This will keep you current when we release crown gall related information.
  • Bring your crown gall questions and concerns to the upcoming Mid-Atlantic Fruit and Vegetable Convention in Hershey PA (February 3, 2016); let’s discuss them.
  • Bryan will discuss current disease updates at the 2016 PA Wine Marketing & Research Board Symposium at the Nittany Lion Inn (University Park, PA) on March 30, 2016.
  • Participate in a series of webinars being organized by Tim Martinson, Cornell University, that will enable growers to tap into Tom Burr’s long standing research program on managing crown gall and what we have to look forward to in the future. Stay tuned for more details later this winter.
  • Check out this recent presentation by Dr. Burr at this link.

Information used in composing this article was from personal communication with Dr. Tom Burr and:

Compendium of grape diseases, disorders, and pests. Second edition. 2015. Wayne F. Wilcox, Walter D. Gubler, and Jerry K. Uyemoto, eds. American Phytopathological Society Press. Pages 95-98.

Tim Martinson and Thomas Burr. How Close are We to Crown Gall-Free Nursery Stock?  Appellation Cornell; Research Focus 2012-1. http://nationalcleanplantnetwork.org/files/144948.pdf

Wine Grape Production Guide for Eastern North America. 2008. Tony Wolf, ed. Natural Resource, Agriculture, and Engineering Service. Cornell Cooperative Extension.

Visiting Vineyards in Erie County and Evaluating Future Winter Injury Management Strategies

By: Michela Centinari

Denise Gardner, Penn State Enology Extension Associate, and I visited the Lake Erie region, Northwest of Pennsylvania, on June 25 and 26, 2015. We first visited the Lake Erie Regional Grape Research and Extension center (LERGREC) and later met with wine grape growers and winemakers at the South Shore Wine Company.  The second day I visited three vineyards with our hosts Andy Muza, the horticulture Extension agent in Erie County, Bryan Hed and Jody Timer, research technologists at Penn State that focus on plant pathology and entomology, respectively.

Regional visits are always a great opportunity to connect with growers and winemakers, discuss production issues, gather information on topics of interest for future educational workshops, and also to learn about grower/winery relationships.

Figure 1. View of vineyards in North East, Pennsylvania.

Figure 1. View of vineyards in North East, Pennsylvania.

The wine industry in the Northwest region of Pennsylvania is growing, both in size and reputation.  Most of the growers I met are experienced juice grape growers transitioning to wine grapes. One of the growers pointed out that he chose, among his 200 acres of existing Concord vineyards, the very best location to plant and grow his Vitis vinifera wine grapes. He had a clear understanding of how site selection is critical to successful cultivation of V. vinifera varieties, and site selection is one of the key areas we discuss with growers upon entering the wine grape industry.

During the two-day visit, most of the discussion focused on winter injury sustained by V. vinifera, inter-specific hybrids and also V. labrusca/native grapevines (mostly Niagara) over the past two winters.  The last two years provided record low temperatures in Erie area during the 2013-2014 and 2014-2015 winters, which have proved challenging for farmers (Figure 2).   Variation in cold hardiness among grape genotypes, the impact of a diversified crop, and vineyard management practices to reduce/minimize future winter injury losses were discussed to great length.

Figure 2. Daily maximum and minimum temperatures recorded at the Lake Erie Research and Extension center during the (a) 2013-2014 and (b) 2014-2015 dormant seasons.

Figure 2. Daily maximum and minimum temperatures recorded at the Lake Erie Research and Extension center during the (a) 2013-2014 and (b) 2014-2015 dormant seasons.

Growers have been busy assessing the extent of winter injury, training suckers to be used as new trunks and cordons (Figure 3) and making re-planting decisions. One industry member pointed out that winter injury losses have forced growers to make strategic decisions in terms of variety selection. It was recommended that growers use this opportunity to substitute varieties that did not produce well with others that are more suited for the region and individual vineyard sites.  In terms of crop diversification, the use of cold-hardy hybrid varieties released by the University of Minnesota may be a viable option for growers, but wineries should be consulted with regards to their interest in those varieties.  Local market opportunities still need to be explored in Pennsylvania with regards to cold-hardy hybrid variety sales in the tasting room.

Figure 3. Riesling vines. The grower has retained all the suckers the vines produced. Two suckers per vine will be trained to be new trunks and cordons.

Figure 3. Riesling vines. The grower has retained all the suckers the vines produced. Two suckers per vine will be trained to be new trunks and cordons.

From a research prospective, these two consecutive severe cold winters provided a good opportunity to evaluate the cold hardiness of V. vinifera and inter-specific hybrid wine grape varieties at the variety evaluation planting established at LERGREC in 2008, as part of the NE-1020 multistate project. For more information about the NE-1020 trial, please refer to the article “NE-1020… What? The Top 5 industry benefits affiliated with the NE-1020 variety trial”  by Denise Gardner.

During our visit we noticed, as expected, further damage to the cold tender V. vinifera varieties. Among the V. vinifera, Grüner Veltliner and Cabernet Franc are recovering better than Pinot Grigio and Pinot Noir, which are either dead to the ground or showing a weak recovery (Figure 4a, b). Very good bud survival was observed in Chancellor (Figure 4c) which produced about 3-4 clusters per shoot despite the extremely cold events recorded over the last two winters. Overall, Marquette, a cold-hardy hybrid variety released by the University of Minnesota, has shown encouraging results. In addition to the cold sensitive V. vinifera varieties, a poor survival was observed in the NY81.0315.17 (Riesling x Cayuga White) selection (NE-1020 vineyard) and in Traminette at several vineyards within the Erie region (Figure 4d).

Figure 4. Grüner Veltliner, Pinot Grigio (a), Cabernet Franc (b) and Chancellor vines (c) at the variety evaluation planting established at LERGREC. Traminette and Vignoles vines at a commercial vineyard located in the Lake Erie region.

Figure 4. Grüner Veltliner, Pinot Grigio (a), Cabernet Franc (b) and Chancellor vines (c) at the variety evaluation planting established at LERGREC. Traminette and Vignoles vines at a commercial vineyard located in the Lake Erie region.

Protecting vines and fruiting potential from winter injury

Growers had several questions about best practices to protect trunks and the fruiting potential of the vines against winter injury.

Hilling up the soil around the vines in the fall and taking out hills in the spring is the most common practice used by growers to protect the graft union and some of the scion tissues above the graft union against low winter temperatures. A few growers showed concerns about the wet conditions of the soil in the fall/spring which makes this operation difficult. Heavy, wet soil may be thrown up under the trellis in large clods which can result in imperfect burial of the vine trunk, and makes the take-out operation difficult [1].  Other growers mentioned using straw, or hay, or plowing snow (if there is sufficient snowfall) around the vines to insulate vine tissues.  In the spring, it is critical to remove the soil around the graft union to avoid scion rooting, which defeats the purpose of rootstock and may result in vine decline [1].

Burying sucker canes under the soil or straw in the fall is a method that can be used to avoid winter injury and insure the retention of a ‘marketable’ crop the following year. A comprehensive description of the ‘burial cane’ technique can be found in: Winter Injury to Grapevines and Methods of Protection, Extension bulletin available for $15.  Growers in Ontario and in New York State used this technique to protect some fruiting potential of the vines.  As a brief explanation, shoots are grown on wires near the ground during the growing season and they are covered with soil or straw in the fall (Figure 5). Another option is to place canes near the ground after the vines go dormant.  “A wire on the ground that is tensioned either permanently or temporarily is very helpful to hold canes near the ground” [1].  The buried canes need to be extracted from the soil as soon as the risk of low winter temperatures is past.

Figure 5. Canes tucked around (a) a plastic bailing twine or (b) a wire. Canes are covered with straw before the winter. Photos credit: Sigel G., Winter Injury to Grapevines and Methods of Protection.

Figure 5. Canes tucked around (a) a plastic bailing twine or (b) a wire. Canes are covered with straw before the winter. Photos credit: Sigel G., Winter Injury to Grapevines and Methods of Protection.

The cane burial technique and its effects on vine bud survival and production have been examined at Cornell University with the help of cooperating growers of V. vinifera varieties. For detailed information on the study please check Understanding and Preventing Freeze Damage in Vineyards: Workshop Proceedings (21-38) [2].

The main finding in this study was:

  • Sucker canes buried in the fall do avoid the freeze injury suffered by the aerial canes of the vines.

However:

  • After canes were unburied, buds appeared to suffer injury unrelated to freezing. Buried canes showed more “blind nodes,” they were less productive (e., significantly fewer clusters) than canes not buried. Buried canes also showed a delayed bud and shoot emergence compared to aerial, not buried canes.
  • Cane burial is not a cheap operation: “typical extra costs per acre for cane burial in the Finger Lakes Region is about $400 to $500. This includes labor needs for laying out ground wire, wrapping them with suckers, hilling, and buried cane extraction, pruning, and tying in spring” [2].

In conclusion:

  • “In normal or warm years, burying cane can result in production and economic losses. However, in extremely cold winters, buried canes allow a “half crop” and no dead vines” [2].

References Cited

  1. Zabadal, TJ, Dami, IE, Goiffinet, MC, Martinson, TE, and Chien, ML (2007) Winter Injury to Grapevines and Methods of Protection. Extension Bulletin E2930. Michigan University Extension.
  2. Goffinet, MC (2007). Grapevine Cold Injury and Recovery After Tissue Damage and

Using Cane Burial to Avoid Winter Injury. In: Understanding and Preventing Freeze Damage in Vineyards, Workshop Proceedings. University of Missouri Extension. 21-38.

 

All of the cool V&E Research Covered at the 2015 PA Wine Marketing & Research Board Symposium

April 22, 2015 marked the 4th annual PA Wine Marketing and Research Board (PA WMRB) Symposium, held at the Nittany Lion Inn in State College, PA. It was a very successful program, hosting over 86 industry members concurrently with the PWA’s Annual Conference, which was held on both April 21st and 22nd. To read more about the PA WMRB, please visit their website here.

In addition to their other tasks, the PA WMRB financially supports a series of research projects, in which topics vary from a multi-state variety trial to frost protection in the vineyard and into experimentation with sulfur-containing aromatic control in wines. All research topics have been identified as prevalent interests to, or “problem areas” for, Pennsylvania industry members, and results have applicability to all producers.

In an effort to expand awareness of the various research programs taking place at Penn State, the following researchers have summarized their talks from the 2015 Symposium. Most of this research is in their beginning stages, and will continue into the current vintage.

All researchers would like to thank the Pennsylvania grape and wine industry and PA WMRB for their continued support.

 

Clonal Selection and New Interesting Varieties for Pennsylvania

By: Diego Barison, NovaVine, Inc.

  • Two Italian white varieties that show potential for Pennsylvania’s growing region include Tocai Friulano and Moscato Giallo. Tocai Friulana is an early ripening variety, has potential for barrel aging from a winemaking perspective. Moscato Giallo tends to have a subdued aromatic profile compared to other Muscat varieties, but on years that Botrytis pressure is high, it will retain a higher crop yield. Moscato Giallo can be used to make still and sparkling wines.
  • Two Italian red varieties that show potential for Pennsylvania’s growing region are Lagrein and Toraldego. Both varieties are common in northern Italy. Lagrein has a good tannin structure and good acidity, which is preferred for red wine aging. Toraldego has been planted at a few vineyards throughout the Mid-Atlantic region.
  • For more information on grape varieties and clonal selection, you can visit NovaVine’s website.
  • Additionally, Vitibook, co-authored by Diego, is a valuable resource for vineyard owners throughout the U.S.

 

Cold Temperature Stress in Grapevine: Impact of Management Practices and Varietal Selection

By: Maria Smith

  • Cold stress is one of the biggest limiting factors to high quality wine grape production in Pennsylvania.
  • Two types of relevant cold stress in PA include
  1. Dormant-season cold injury
  2. Late spring frost injury
  • Current experiments that I am involved with to evaluate management practices and varietal selection on impacts of cold stress:
  1. Crop load regulation using early leaf removal and cluster thinning, evaluating 2 over-cropping varieties: Chancellor (hybrid) in 2014 and 2015, and Gruner Veltliner (vinifera) in 2015 and 2016.
  2. Variety evaluation in 2015 for tolerance and recovery from late spring frost event. Which includes 4 potted varieties: Marquette (hybrid), Le Crescent (hybrid), Riesling (vinifera) and Lemberger (vinifera). These varieties will be exposed to an artificial frost ‘event’ at 26.5-28°  The physiological response and recovery of vines will be monitored.

 

The Role of Copper in the Evolution of Sulfur Compounds in Wine

By: Gal Kreitman

  • In order to mitigate wine oxidation, reductive winemaking is becoming more commonplace.
  • Reductive winemaking preserves important varietal thiols which provide aroma characteristics of passionfruit, grapefruit, citrus zest, blackcurrant. Reductive winemaking also preserves reduced sulfidic odors such as hydrogen sulfide and methanethiol.
  • Winemakers commonly add copper to wine to remove the reduced odors which very quickly removes hydrogen sulfide and methanethiol.
  • Copper does have downsides as it doesn’t remove disulfides and thioacetates which can significantly contribute to reduced odors in wine.
  • Copper can also remove some of the beneficial varietal thiols.
  • Residual copper in wine post-bottling can actually lead to higher formation of reduced odors in wine and other redox mediated reactions.
  • My research goals are to elucidate the mechanism for copper-mediated thiol redox reactions, and provide winemakers with tools to have a better control over sulfur-containing aroma compounds.

 

Assessing Spotted Wing Drosophila Injury Potential on Grape Production

By: Jody Timer and Michael Saunders

Spotted wing drosophila (SWD), Drosophila suzukii, is an invasive vinegar fly that was introduced into the United States in 2008. It was introduced into Pennsylvania in 2010. S. suzukii is a highly polyphagous pest, whose serrated ovipositor allows it to lay its eggs on undamaged ripening fruit. Adult females can lay 100 to 600 eggs in fruit, as the fruit starts to color and sugar levels begin to rise. SWDs’ lifecycle consists of adults, eggs, larva (3 instars) and pupa overwintering as adults. They differ from other fruit flies because of the serrated ovipositor which allows them to infest intact fruit by laying eggs inside of the undamaged fruit. Damage is often not discovered until the fruit goes to market. SWD is considered a major problem in grape vineyards and damage to wine grape crops has been reported in many states.

Red traps containing yellow sticky cards, baited with apple cider vinegar and the new dual Trece lure have shown to be the most effective and easiest way to trap SWD. Trapping is the most efficient way to determine if SWD is in a vineyard, and also to determine when it is time to check the grapes for infestation. Trapping in Erie County has shown that the SWD are appearing earlier each year, and the numbers of insects captured in the traps is increasing with each subsequent year. The best way to check for infestation in the vineyard is to add crushed grape berries to salt solution: 1 cup water to ¼ cup salt and the larva will float to the top. Larva found in recently ripened fruit is most likely SWD. SWD was discovered from emergence studies on Concord, Chambourcin, Niagara, and Vidal. No-choice, 2-choice-and 4-choice studies were conducted on these four grape varieties. All varieties in the no-choice trials were infested with SWD. They showed a slight preference for Niagara grapes in the 2 and 4 choice testing. Research was done bagging clusters with net bags containing SWD. All clusters became infected with SWD after being bagged. Pesticides in three activity groups have shown efficacy against SWD. It is not recommended to spray unless you have a known infestation in your vineyard.

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Updates on Grape Disease Management Research

By: Bryan Hed

Early leaf removal and Botector for bunch rot control:

  • Bunch rot control = fruit wound control. Many factors cause wounds to fruit: birds, insects, powdery mildew, cluster compactness. We typically make great efforts to minimize the effects of all of these factors, with the exception of compactness.
  • Compactness creates wounds that cause direct fruit rot. Compactness also activates latent Botrytis infections, increases the effect of retained bloom trash in clusters on bunch rot development, and reduces pesticide penetration into clusters.
  • We have investigated many methods of reducing cluster compactness over the years, and early leaf removal has been the most consistently effective method. Mechanization of this method will improve its cost effectiveness and increase adoption.
  • Botector, a biological pesticide was compared to synthetic fungicides and early leaf removal for control of bunch rot disease on Chardonnay and Vignoles grapevines.
  • Botector was not effective in either trial, but fungicides and early leaf removal were equally effective at reducing bunch rot disease, when compared to the control. An integrated treatment of both fungicides and early leaf removal was the most effective treatment.

The effects of rainfall on fungicide (Mancozeb) residue retention.

  • Mancozeb is one of the most widely applied fungicides for grape disease control. We monitored the effects of rainfall on mancozeb residues on grapevine leaves.
  • Over two seasons, high pressure liquid chromatography (HPLC) and inductively coupled plasma mass spectrometry (ICP) were used to quantify mancozeb residues on grape leaves. Both methods were equally effective in year one, but ICP appeared to be more effective and consistent in year 2. As ICP is less expensive and samples are easier to store, its use for quantifying mancozeb residues may improve the accuracy and reduce the cost of this research.
  • In the field, the first inch of rain removes about 60-70% of mancozeb residue, the second inch 70-80%, and the third inch 80-90% of the mancozeb residue.
  • Future research will focus on bioassays to determine the efficacy of varying concentrations of rain challenged mancozeb residues for disease control and the need for subsequent fungicide applications.

 

Wine Marketing Strategies for the Mid-Atlantic Region

By: Abigail Miller

  • Social media is a conversational marketplace; not just two-way, it’s multi-way.
  • Two-thirds of core wine drinkers (those who drink wine about once a week) and 40% of marginal wine drinkers (those who drink wine less frequently) use the Internet in some form to get information about wine (Guenther, 2013).
  • At least 30% of survey participants felt that a Facebook Page was mandatory for a winery. Fifty-four percent of 21- to 24-year-olds, specifically, responded in this manner.
  • Though percentages for Instagram were lower, 18.3% of those 21- to 24-year-olds responded that this tool is mandatory.
  • Younger Millennials are the primary users of Instagram and winery tasting rooms should consider posting on this network to reach these consumers.
  • Websites for promoting products and promoting purchases should be also be a part of a winery tasting room’s repertoire.
  • Content for all outlets could focus on serving and pairing suggestions, coupons, promotions, and discounts, as well as other components that appealed to survey participants.

To read more about Abby’s study on social media preferences for wineries, please visit:

 

Evaluation of Cost Effective Practices for Reducing the Risk of Spring Frost Injury in Vineyards

By: Michela Centinari

Michela presented the main findings from of a project started in 2014 to evaluate the potential of low-cost strategies to reduce the risk of spring frost injury in grapevines. Specifically two spray-on materials currently used by grape growers across the country were tested for their ability to delay budbreak (Amigo oil, soybean- based oil) and provide frost protection to young grapevine shoots after budbreak (KDL, potassium dextrose lactose; Agro-K corporation). Briefly, Amigo oil caused higher levels of delay in bud-break in V.vinifera varieties (Riesling and Lemberger) than in the hybrids varieties (Noiret and Traminette) (Figure 1). Current research efforts are investigating if the different response observed among varieties may be related to the time of oil application. In the vinifera varieties the delay in budbreak was followed by a significant reduction in yield (about 40%), with no effect on fruit composition and wine chemical parameters. Since no frost occurred in Pennsylvania in 2014 the effect of KDL was tested on 1-bud cuttings using a temperature controlled chamber. Preliminary results were shown together with current research efforts which include: testing the effect of KDL on potted vines using a controlled temperature chamber, and at multiple vineyard sites in case a frost event will occur in the next few weeks.

Figure 1. Control and oil-treated Riesling vines (May 20, 2014).

Figure 1. Control and oil-treated Riesling vines (May 20, 2014).

 

The Effect of Acetaldehyde on Red Wine Color Stability and Astringency

By: Marlena Sheridan

  • Wine oxidation can be risky for wines due to side effects of oxygen exposure, but there are important benefits of oxidation for red wines.
  • Acetaldehyde, typically formed from oxygen integration, leads to beneficial effects on red wine color and mouthfeel by binding with tannins and anthocyanins.
  • Reactions with acetaldehyde form stable, polymeric pigments as well as modified tannins with lower perceived astringency.
  • Winemakers use oxygenation techniques (e.g., micro-ox, barrel aging) to form acetaldehyde in the wine, but this includes the risk of detrimental effects of oxidation instead of acetaldehyde formation.
  • Our work aims to evaluate the efficacy of exogenous acetaldehyde treatment of red wine on improving color stability and astringency. This work will be done in real and model wine systems to fully understand the effects of acetaldehyde on wine tannins.
  • Further detail and a description of completed work can be found in my blog post from April 24.

 

The 2014 NE-1020 Variety Trial Harvest: A Comparison of North East and Biglerville, PA

By: Michela Centinari & Denise M. Gardner

Michela Centinari gave an update on the 2014 viticulture performance for the V. vinifera and inter-specific hybrids winegrape varieties established at the two variety evaluation plantings located at the Lake Erie Regional Grape Research and Extension Center (LERGREC), North West side of PA, and at the Fruit Research and Extension Center (FREC) in the southern side of PA (Table 1). The two plantings were established in 2008 as part of the NE-1020 project, a multi-state project that was developed to 1) evaluate the viticultural characteristics and wine quality potential of grape cultivars and clones of economic significance throughout the eastern US; and to 2) characterize the viticultural and wine quality potential of emerging cultivars based on regional needs.

The presentation mostly focused on winter cold temperature injury sustained by the grapevines at the two sites and on the different ability of the varieties to adapt and recover to extreme cold conditions experienced in PA in the winter of 2013-2014.

At the Lake Erie (LERGREC) planting all the vinifera varieties experienced extensive winter injury. Bud, trunk injury and crown gall symptoms were observed in all the vinifera varieties. High incidence of vine mortality was recorded in Syrah, and Muscat Ottonel. Among the vinifera varieties Cabernet franc and Grüner Veltilner vines recovered the best; healthy suckers grew from above the graft union. Lower levels of winter injury were recorded in the Southern part of PA. The most significant winter injury was observed in Tannat (almost 100% bud mortality and vascular tissue damage at cane and trunk levels). The damage on the other varieties was mostly limited to primary buds, although some vines (mostly Syrah, Malbec) sustained vascular tissue damage and collapsed throughout the summer. As a consequence of primary bud damage varieties such as Malbec, Albarino and Cabernet Sauvignon produced very low crop yield.

Table 1. List of varieties and clone designation, when known, planted at the Lake Erie Regional Grape Research and Extension Center (LERGREC), North West side of PA, and at the Fruit Research and Extension Center (FREC) in the southern side of PA.

Table 1. List of varieties and clone designation, when known, planted at the Lake Erie Regional Grape Research and Extension Center (LERGREC), North West side of PA, and at the Fruit Research and Extension Center (FREC) in the southern side of PA.

  • In 2014, 6 varieties were fermented for winemaking trials, and discussed at the recent Symposium: Vidal Blanc (North East), Chambourcin (North East), Cabernet Sauvignon (Biglerville), Merlot (Biglerville), Albarino (Biglerville), and Cabernet Franc (Biglerville).
  • The primary trend noted with Albarino is the continued low yield, which has been annually estimated at under 2.0 tons/acre since 2011. In 2014, the estimated yield for Albarino was 0.57 tons/acre.
  • The Vidal Blanc underwent a pre-fermentation juice trial based on Jose Santos’s presentation in August 2014, which can be found here. Vidal Blanc was separated into three treatment groups: Control (Brown Juice), SO2 addition, and AST addition. Attendees at the PA WMRB Symposium had the opportunity to taste wines produced from these treatments.

 

Pre-Fermentation Juice Treatments in Vidal Blanc. All treatments treated with pectinase and 24-hour settling time in cold storage. Image shown after racking.

Pre-Fermentation Juice Treatments in Vidal Blanc. All treatments treated with pectinase and 24-hour settling time in cold storage. Image shown after racking.

Chambourcin Wines in 2013 Vintage Year Showing Red Color Intensity Differences Between 2 Vineyard Sites in PA.

Chambourcin Wines in 2013 Vintage Year Showing Red Color Intensity Differences Between 2 Vineyard Sites in PA.

In addition to the support of the PA Wine Marketing and Research Board, this material is based upon funding provided by the National Institute of Food and Agriculture, U.S. Department of Agriculture, under agreement No. 2010-51181-21599.

Investigating the Inadvertent Transfer of Vitis labrusca Associated Aromas to Vitis vinifera Wines

By: Jared Smith

Polymers, such as plastics used during winemaking, can scalp (uptake) aroma compounds from juice and wine.

Aroma scalping can lead to not only the loss of desirable aromas, but also the presence of unexpected aromas in wines due to desorption of the aromas from the polymers during subsequent processing. This could especially be an issue when equipment is shared for the processing of two completely different species of grapes (ex. V. vinifera vs. V. labrusca) that have vastly different aromatic profiles.

One potential way to help remove scalped aromas from your polymeric winemaking materials is through the use of ethanolic (80%) cleaning solutions at higher temperatures (75°C) for an extended period of time.

Grapevine cold injury, end of the season considerations

By: Michela Centinari

I imagine as winter approaches one thought on every grower’s mind is: “Is this winter going to be anything like the previous one?”

The winter of 2013/2014 was one of the most severe since 1994 and we can hope another 20 years or more pass before we must endure another of the same magnitude. The extent of damage and crop loss varied among regions, individual vineyard sites, wine grape varieties (Figure 1) and the health of the vines going into the cold season. In this regard, during a vineyard visit in Chester County (Southeast Pennsylvania) in August, a grower pointed out a block of Cabernet Franc (Vitis vinifera L.) vines with winter cold injury symptoms. The vines had a healthy green canopy but, surprisingly, no clusters. That was unusual because other Cabernet Franc vines in the area were fine. However, the grower highlighted that those vines had already experienced severe frost damage in the previous spring (2013). Frost damage may contribute to a low overwinter carbohydrate reserve and negatively affect bud cold hardiness as well as the development of shoots and inflorescences in the following spring. Concentrations of non-structural carbohydrates are closely related with cold hardiness in grapevine buds and canes [1].

Figure 1. Cold damage at Lake Erie Regional Grape Research and Extension Center vineyard. In the front: cold sensitive Syrah (V. vinifera  L.) vine killed back to the ground.  In the back: Healthy cold hardy Marquette (Vitis spp.) vines.

Figure 1. Cold damage at Lake Erie Regional Grape Research and Extension Center vineyard. In the front: cold sensitive Syrah (V. vinifera L.) vine killed back to the ground. In the back: Healthy cold hardy Marquette (Vitis spp.) vines.

Could delaying fruit harvest for ice wine production negatively affect vine health and compromise winter bud cold-hardiness?

A recent 5-year study conducted in Ohio reported that neither crop level (16 vs 32 clusters per hedgerow meter) or harvest date (beginning of October vs middle of December) had an impact on winter bud cold-hardiness in ‘Vidal blanc’ vines [2]. This is very good news for growers. However, as the authors suggested, the effect of crop level on cold hardiness may depend on the variety [3] and its vegetative and reproductive characteristics (i.e., tendency for excessive vigor and/or over-cropping).

Ongoing research at Penn State is being conducted to assess the impact of crop load management practices on bud cold acclimation, de-acclimation, and maximum cold hardiness, as well as carbohydrate reserve storage. We plan on highlighting these developments as results are determined over the next few years.

 How to assess cold injury in grapevine, and manage cold injured vines?

After budbreak, when the extent of the damage started to become more clear, many growers wondered how to assess the extent of the damage and what the best practices were for rapid vine recovery. Our grape and wine team at Penn State put together a list of resources to help growers during this difficult growing season. Here are some of those resources:

You can start reading the article published on eXtension Cold Injury in Grapevine by Mark Chien, former Penn State Viticulture Extension educator and now Program Coordinator, Oregon Wine Research Institute, and Michelle Moyer, assistant professor at Washington State University. At the end of the article you can find of comprehensive list of recommended resources that can be used to assess and manage cold damage in the vineyard. Among these resources I would like to highlight:

Other resources that you may find useful are:

  • Managing Winter-Injured Vines published on Appellation Cornell, June 2014, by Tim Martinson (Senior Extension Associate, Cornell University);.
  • Managing Winter Injury published on the Lake Erie Regional Grape Program, Cornell University, Viticulture Notes, Issue # 3, June 2014, by Kevin Martin (Penn State University, LERGP Business Management Extension Associate). The article provides useful guidelines of the cost associated with re-training and re-planting a vineyard.

What did we learn?

The severe cold winter provided a good opportunity to evaluate the cold hardiness of Vitis vinifera and inter-specific hybrid wine grape varieties at the two variety evaluation plantings established in Pennsylvania (PA) in 2008, as part of the NE1020 multistate project. The two plantings are located at the Lake Erie Regional Grape Research and Extension Center (LERGREC, Northwest Pennsylvania) and at the Fruit Research and Extension Center (FREC) in the southern side of PA. For more information about the NE-1020 trial please refer to the article “NE-1020, What? The Top 5 Industry Benefits Affiliated with the NE-1020 Variety Trial” by Denise Gardner.

At the LERGREC station all the V. vinifera varieties experienced extensive winter injury. High incidence of vine mortality was recorded in Syrah, and Muscat Ottonel; trunk injury was mostly observed in Pinot Noir and Pinot Grigio. Among the V. vinifera varieties, Cabernet Franc and Grüner Veltilner vines are recovering the best; healthy suckers are growing from above the graft union and they will be used for trunk renewal next spring. For information regarding the level of bud injury observed on the 17 grapevine varieties established at the LERGREC site please refer to the article “Grape Growing in PA In Spite of the Weather” by B. Hed and M. Centinari

As expected, lower levels of winter injury were recorded at the FREC station in the Southern part of Pennsylvania. The most significant winter injury was observed in Tannat (almost 100% vine mortality). Some of the other varieties experienced cold damage, limited primarily to primary buds. Although, some of the Syrah and Malbec vines suffered conductive tissue damage (phloem and xylem) and collapsed during the summer (Figure 2).

Figure 2. Cold damage at the FREC vineyard. Syrah (V. vinifera L.) vines collapsed during the summer because of conductive tissue damage (phloem and xylem).

Figure 2. Cold damage at the FREC vineyard. Syrah (V. vinifera L.) vines collapsed during the summer because of conductive tissue damage (phloem and xylem).

As a consequence of primary bud damage some of the V. vinifera varieties produced low crop yield (Table 1). Specifically, average yields of Malbec, Albarino and Cabernet Sauvignon were much lower than those of the previous season (second column, Table 1). Cluster number per vine in Sangiovese and Viognier were lower than usual. Data such as “percent live buds per total buds left (% live buds/total buds)” and “shoot number per vine” were also recorded. This will provide a comprehensive picture of the differences among the genotypes and their ability to adapt to extreme environmental conditions such as the cold temperatures we experienced in the winter of 2014.

Table 1. Yield components of 20winegrape cultivars in the NE-1020 cultivar trial at Fruit Research and Extension Center (FREC) in the southern side of PA. Vines spacing is 6’ between vines and 9’ between rows.

a - Yield data and cluster data were not recorded due to high levels of bird damage. b - Production data were not recorded due to high level vine mortality.

a – Yield data and cluster data were not recorded due to high levels of bird damage.
b – Production data were not recorded due to high level vine mortality.

Work cited:

  1. Jones, K.S., J. Paroschy, B.D. McKersie, and S.R. Bowley (1999). Carbohydrate composition and freezing tolerance of canes and buds in Vitis vinifera. J. Plant Physiol. 155:101-106.
  2. Dami I.E., S. Ennahli, and D. Scurlock (2013). A Five-year Study on the Effect of Cluster Thinning and Harvest Date on Yield, Fruit Composition, and Cold-hardiness of ‘Vidal Blanc’ (Vitis spp.) for Ice Wine Production. HortScience 48(11):1358–1362.
  3. Dami, I.E., D.C. Ferree, S.K. Kurtural, and B.H. Taylor (2005). Influence of cropload on ‘Chambourcin’ yield, fruit quality, and winter hardiness under midwestern United States environmental conditions. Acta Hort. 689: 203–208.

Harvest 2014: An update to studies on frost injury

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.

Harvest 2014:

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.

Fig 1. Left: Lemberger at harvest (10/9/2014), Right: Riesling at harvest (10/16/2014)

Fig 1. Left: Lemberger at harvest (10/9/2014), Right: Riesling at harvest (10/16/2014)

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.

Figure 2.  Lemberger yield data, 2014

Figure 2. Lemberger yield data, 2014

Winemaking:

 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).

Figure 3.  Lemberger processing at the PSU Food Science Wet Pilot Plant

Figure 3. Lemberger processing at the PSU Food Science Wet Pilot Plant

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.

Table 1.  Juice analysis – Brix, pH, TA of Lemberger and Riesling.  Riesling was chapitalized to 21 Brix.

Table 1. Juice analysis – Brix, pH, TA of Lemberger and Riesling. Riesling was chapitalized to 21 Brix.

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

 

Literature:

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

 

Funding:Print

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.

 

Acknowledgments:

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.