Ensure Your Wines are Stable Before Bottling

By: Denise M. Gardner

It’s that time of year again: bottling time! The past year’s vintage is slowly starting to take up too much room in the cellar and now is the time for decision making in terms of preparing for the pending vintage.  Finalizing a good bottling schedule before harvest starts is an essential good winemaking practice, but bottling comes with its own set of challenges.

It is not uncommon for winemakers to express feelings of “not being able to sleep at night” when wines get bottled, as they are worried about possible re-fermentation issues.  As wine naturally changes through its maturity, it is easy to feel insecure about bottling wines, especially those wines that may have had challenges associated with it throughout production.

However, there are several analytical tests that winemakers can add to their record books every year to ensure they are bottling a sound product.  The following briefly describes a series of analytical tests that provide information to the winemaker about stability and potential risks associated with the product when it goes in bottle.

Bottling comes with its own set of challenges and risks, but several analytical tests can help put a winemaker’s mind to ease regarding bottle stability. Photo by: Denise M. Gardner

Basic Wine Analysis Pre-Bottling:

This first list is the bare minimum data that should be measured and recorded for each wine getting bottled, regardless of the wine’s variety or style.  Keeping accurate records of these chemistries is also helpful in case something goes wrong while the bottle is in storage or after it is purchased by a customer.

pH

pH is essential to know as it gives an indication for the wine’s stability in relation to many chemical factors including sulfur dioxide, color, and tannin.  For example, high pH (>3.70) wines provide an indication that more free sulfur dioxide is needed to obtain a 0.85 ppm molecular free sulfur dioxide content.  At the 0.85 ppm molecular level, growth of any residual yeast and bacteria in the wine should be adequately inhibited.

High pH wines tend to have issues with color stability.  At this point, color stability can be addressed by blending or with use of color concentrates (e.g., Mega Purple).  Keep in mind that if the wine is blended with another wine, all chemical analyses, including pH, should be completed on the blend (as opposed to average individual parts) prior to bottling.

Free and Total Sulfur Dioxide Concentration

In the United States, total sulfur dioxide is regulated and must fall under 350 mg/L for all table wines (CFR: https://www.ecfr.gov/cgi-bin/text-idx?SID=eddaa2648775eb9b2423247641bf5758&mc=true&node=pt27.1.24&rgn=div5#sp27.1.24.a).

However, the free sulfur dioxide concentration provides an indication to the winemaker regarding antioxidant strength and perceived antimicrobial protection.  To inhibit growth of yeast and bacteria during bottle storage, a 0.85 ppm molecular free sulfur dioxide concentration must be obtained.  The free sulfur dioxide concentration required to meet the molecular level is dependent on pH.  Therefore, free sulfur dioxide additions should be altered and based on a wine’s pH for optimal antimicrobial protection.

Analytically, it can be daunting to measure free sulfur dioxide as the wet chemistry set up looks intimidating.  However, many small commercial wineries have benefited from the integration of a modified aeration-oxidation (AO) system, and with a little practice, have been relatively successful at monitoring free sulfur dioxide concentrations.  A few wineries have worked to validate use of Vinmetrica’s analyzer (https://vinmetrica.com/), and found results comparable to those obtained by use of the AO system.

Residual (or Added) Sugar

Any remaining sugar in the bottle, whether through an arrested fermentation or direct addition, can pose a risk for re-fermentation post-bottling.  This is especially true if the winery lacks good cleaning and sanitation practices.  Nonetheless, it is a good idea to assess the sugar content pre-bottling to record a baseline value of the sugar concentration going into bottle.  If bottles were to start re-fermenting, a sugar concentration could be analyzed and used to compare against the baseline value in order to assess the potential of yeast re-fermentation.

For wineries with minimal residual sugar concentrations, a glucose-fructose analysis (often abbreviated glu-fru) is often used to help determine accurate sugar content.  For wines with added sugar an inverted glucose-fructose analysis may be required.

If you are concerned about potential risk for Brettanomyces (Brett) bloom post-bottling, it is usually encouraged to reduce the sugar content in the finished wine below 1% (<10 g/L sugar) in the bottle.

Malic Acid Concentration

While using paper chromatography to monitor malolactic fermentation (MLF) is useful, it does not give an accurate reflection of residual malic acid concentration.  In fact, some winemakers find that a paper chromatogram may show a MLF has been “completed,” but would prefer to have lower residual malic acid concentrations remaining in the wine.

During my time at an analytical company, 0.3 g/L of malic acid and below was considered “dry.”  This is typically a safe level of residual malic acid to avoid post-bottling MLF.

Volatile Acidity

Volatile acidity (VA) is federally regulated, and levels are indicated in the Code of Federal Regulations (CFR: https://www.ecfr.gov/cgi-bin/text-idx?SID=eddaa2648775eb9b2423247641bf5758&mc=true&node=pt27.1.24&rgn=div5#sp27.1.24.a).  For most states, with California as an exception, the maximum allowable VA for red wines is 1.40 g/L acetic acid (0.14 g/100 mL acetic acid) and for white wines is 1.20 g/L acetic acid (0.12 g/100 mL acetic acid).

Monitoring VA through production is a good indicator of acetic acid bacteria spoilage.  At minimum, wineries should record VA

  • immediately post-primary fermentation,
  • post-MLF,
  • periodically through storage (e.g., every 2-3 months) and
  • pre-bottling.

Whiling monitoring VA, sharp increases in VA should alarm the winemaker of some sort of contamination.  Typically, these increases are caused by acetic acid bacteria, which can only grow with available oxygen.

Alcohol Concentration

As a general rule of thumb, knowing the final alcohol concentration is a good idea.  Alcohol content helps determine a tax class for the wine and is required for the label.

 

Extra Analysis:

Titratable Acidity (TA)

All wines are acidic in nature as they fall under the pH 7.00.  However, titratable acidity (TA) acts as an indicator for the sour sensory perception associated with a given wine.  For example, two wines, Wines 1 and 2, with a pH of 3.40 may have different TAs.  If Wine 1 has a TA of 8.03 g/L tartaric acid while Wine 2 has a TA of 6.89 g/L tartaric acid, Wine 1 would likely taste more acidic (assuming all other variables are the same).

Titrations are an easy analytical testing method to learn and understand when testing wine’s chemistry. Photo by: Denise M. Gardner

Cold Stability

Cold stability tests are often recommended to ensure the wine is cold stable, and will, therefore, not pose a threat of precipitating tartrate crystals during its time in bottle.  Not all wines require a cold stability process (e.g., seeding and chilling).  Cold stability testing can be done prior to a cold stabilization step in order to avoid extraneous processing operations, saving time and money.

For more information on cold stability processes and testing, please visit Penn State Extension’s website: http://extension.psu.edu/food/enology/analytical-services/cold-stabilization-options-for-wineries

These crystals on this cork illustrate what can happen when a wine is not properly cold stabilized. While the tartrate crystals pose no harm to consumers, they may find the crystals unappealing or questionable. Photo by: Denise M. Gardner

Protein Stability

Additionally, haze formation is a potential risk post-bottling.  While hazes do not typically offer any safety threat to wine consumers, they often look unappealing.  Protein hazes tend to make the wine look cloudy.  Some varieties are more prone to protein hazes then others, and running a protein stability trial could minimize the risk for a protein haze in-bottle.

It is important to remember that due to the fact protein stability is influenced by pH, cold stability production steps should take place before analyzing the wine for protein stability and before going through any necessary production steps to make the wine protein stable.  This is due to the fact that cold stability processes ultimately alter the wine’s pH, and the chemical properties of proteins are influenced by the pH.

 

Analysis for Those that May Consider Bottling Unfiltered:

Yeast and Bacteria Cultures (Brett, Yeast, Lactic Acid Bacteria, Acetic Acid Bacteria)

Having a microscope in the winery can be a great reference point in terms of scanning for potential microbiological problems.  However, if the winery does not have a microscope, but knows that some microbiological issues or risks may exist in a wine, having a lab set test the wine on culture plates is a good indicator for potential growth risks during the wine’s storage.

If the wine is going to be bottled using a sterile filtration step, keep in mind that wines are not bottled sterile.  Assuming the absolute filtration method is working properly, the wine has potential to become re-contaminated with yeasts and bacteria from the point of which it exits the filter.  In fact, it is not uncommon for wines to pick up yeast or bacteria contamination during the bottling process.

Managing free sulfur dioxide concentrations can help inhibit any potential growth from contamination microorganisms if the proper antimicrobial levels (0.85 ppm molecular) are obtained at that wine’s pH and retained during the bottle’s storage.

4-EP and 4-EG Concentrations for Reds

For wines that may have had a Brettanomyces (Brett) bloom, knowing the concentrations of 4-EP and 4-EG in the wine going into bottle is a good result to keep on file.  If a Brett bloom occurs later in the bottle, it is likely (although, not guaranteed) that the volatile concentration of 4-EP and/or 4-EG may increase and confirm the problem.

Furthermore, evaluating a wine for 4-EP and 4-EG concentrations can also help isolate a possibility of Brett existence, especially if their concentrations are below threshold.  However, it should be noted that both compounds can also exist in wines that are stored in wood, even without a Brett contamination.

Double Check: PCR for Reds

Brett can be a tricky yeast to isolate and identify.  It is usually recommended to run multiple analytical tests related to Brett in order to confirm its existence or removal from a wine.  While culture plating identifies living populations of microorganisms, PCR cannot typically differentiate between live and dead cells as it is measuring the presence of DNA.  A microorganism’s DNA can get into a wine after yeast death and through autolysis.  Therefore, a positive PCR result for Brettanomyces is hard to confirm if the result includes live cells, dead cells, or a combination of both.

Culture plating can help confirm the presence of active, live cells, but the success rate of growing Brettanomyces in culture plates is variable.

Nonetheless, scanning wines by PCR for Brett can help winemakers isolate a general presence and risk of Brett in their wines.

Wine samples prepare for analytical evaluation. Photo by: Denise M. Gardner

Still Worried About Your Wine Post-Bottling?

Bottle sterility

Bottle sterility testing is helpful, especially when a winemaker wants to ensure wines have been bottled cleanly.  For this type of testing, it is best to sample a few bottles

  • at the beginning of a bottling run,
  • immediately before any breaks,
  • immediately after any breaks, and
  • at the end of a bottling run.

Bottles can, again, be evaluated under a microscope and evaluated for the presence of microorganisms.  Bottles can also be sent to a lab for culture plating.  The growth of yeasts or bacteria from culture plates at this stage indicates a failure of the sterile filtration system or contamination of the wine post-filtration.  Clean wines, obviously, should help put a winemaker’s mind at ease as it matures in bottle.

Ensuring a wine’s stability post-bottling is a challenge.  However, with proper cleaning and sanitation methods coupled with the right analytical records, winemakers can reduce their worry.  For information on any of these topics, please visit:

 

2017 Summer Disease Management Review

By: Bryan Hed

As we move into the post-bloom period, we are reminded that the immediate pre-bloom spray and the first post bloom spray are the most important you’ll make all season. These two sprays protect the nascent crop during its most vulnerable period and are essential to a fruit disease management program for control of the four major grape diseases; powdery and downy mildew, black rot, and Phomopsis. Use ‘best’ materials, shortest intervals, best coverage, etc., for those two sprays, EVERY YEAR! No matter what varieties you grow, those two sprays are the most important for protection of your crop. For growers of Vitis vinifera and many of the French hybrids, the second and perhaps third post-bloom sprays are also of critical importance, especially in a wet year and in vineyards that have already developed some observable level of disease this season. That said, let’s review these major diseases.

First, there’s Black rot caused by the fungus Guignardia bidwellii. This fungus can infect all immature green parts of the vine: fruit, shoots, leaves, and tendrils. On leaves, infections start out as small light green spots visible on the upper surface gradually turning brown to reddish-tan as infected tissue dies (Figure 1). Small, black, pimple-like bodies (pycnidia) develop inside the spot or lesion, usually arranged in a loose ring just inside the dark brown edges of the spot (Figure 1). Spores of the fungus are formed within pycnidia, and are released and splashed around during rainfall periods. Leaves remain susceptible as long as they are expanding and the size of leaf lesions indicate when, during expansion, the leaf was infected. For example, small lesions result when leaves become infected near the end of their expansion. Large lesions indicate the leaf was infected early in expansion. However, numerous small lesions, when clustered, may coalesce to damage large portions of the leaf. The death of large portions of the leaf blade may cause the entire leaf to die and abscise, but this is rare. On petioles, black, elongated lesions may induce wilting or abscission of leaves. Infections on berries initially appear as small, tan spots that develop a dark outer ring and expand rapidly to rot the entire berry. The brown berry shrivels into a hard, black, wrinkled mummy studded with spore producing pycnidia (Figure 2). Once the caps come off during bloom, berries of most varieties are highly susceptible for about 3-4 weeks, gradually developing resistance 5-6 weeks after capfall. Infections that take place during peak susceptibility generally show symptoms within 10-14 days. As berries develop resistance to black rot, the time for infections to become manifest takes longer, and infections that occur toward the end of the susceptibility period (second half of July?) may not develop symptoms until veraison.

Fig. 1 Development of black rot lesions on grapevine leaf (Concord).

 

Fig. 2 Development of black rot lesions on grape berry (Concord).

On shoots, lesions appear as elongated or elliptical brown cankers. Pycnidia may be clumped in the center of the lesion and/or line the margins of the lesion (Figure 3). These pycnidia produce spores during the current season and can be a source of further infection to fruit. These lesions remain on the shoots after they have “hardened off” and can survive over winter to release spores again the following spring. Large shoot lesions may render the shoots susceptible to breakage by wind, but this is rare.

Fig. 3 Black rot shoot lesions (Concord).

As berries develop resistance, the appearance of new infections may change: circular lesions are black, expand more slowly, and may remain small, often failing to affect the entire berry (Figure 4). Likewise, leaf infections that take place at the very end of the susceptibility/expansion period may become manifest as small dark pinhead size spots that do not expand (Figure 4).

Fig. 4 Limited black rot lesion development from infections occurring toward the end of the susceptibility period (Concord).

Cultural and chemical control:

The black rot pathogen survives the winter in infected grape tissue (primarily fruit mummies) which serves as a source of inoculum (spores) the following season.  Inoculum that remains in the trellis poses a much greater risk than inoculum dropped to the ground. Therefore, one of the most important methods of cultural control of black rot is removal of infected material, particularly fruit and cluster material, from the trellis. Once on the ground, mummy viability is reduced to further improve control. To take matters a step further, row middles can be plowed and hilling up under the row can bury mummies directly under vines. Maintaining an open canopy where fruit and other susceptible tissue dry out as quickly as possible after rainfall, will also help reduce this disease and improve fungicide penetration and coverage of the fruit.

Chemical control options for black rot mostly include two modern active ingredient classes like the strobilurins (azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin) and the sterol inhibitors (tebuconazole, tetraconazole, difenoconazole, myclobutanil) as well as the old standards like captan, mancozeb, and ziram. All are quite effective. The strobilurins and sterol inhibitors are more rainfast than the old standards and the sterol inhibitors have the capacity to stop the progress of an existing infection if applied within about 3 days after the infection period.

Scouting can be an important part of a black rot control program. The presence of pre-bloom leaf infections, especially those in the fruit zone, may indicate the presence of an over-wintering source of inoculum in the trellis and high risk of fruit infection after capfall. Fruit infections can occur during bloom and anytime up to 5-6 (native varieties) to 7-8 (Vitis vinifera) weeks after bloom.

In most parts of Pennsylvania, downy mildew first became active during the second half of May; at about the 5-6 leaf stage of grapevine development. Up here along the southern shore of Lake Erie, our first infection period occurred on May 25 (rainfall with temperatures above about 52 F) and first symptoms were observed at our farm on unprotected suckers of Chardonnay on June 1 (about 6-7 days after infection). On leaves, the first infections of downy mildew appear as yellowish ‘oil spots’ on the top of the leaf that coincide with a white, fluffy or downy patch of sporulation on the lower surface. On young shoots and clusters, early symptoms may first cause cluster rachises and shoots to thicken and curl (Figure 5).  As the pathogen, Plasmopara viticola, aggressively colonizes young, expanding grape tissue, infected shoots, clusters, and leaves may turn brown and die. When berries are infected later in the season their development is hindered and they fail to soften at veraison, turning a pale mottled green (white varieties) to red or pink (red varieties, Figure 6). Inflorescences and fruit clusters are most susceptible from about 2 weeks pre bloom to about 2 weeks post bloom. Highly susceptible varieties will require protection through 3-4 weeks post bloom because cluster stem tissue may remain susceptible until later in the season (after fruit have already become resistant) and cluster stem infections can still result in fruit loss. Young leaves and shoots are very susceptible, but become somewhat more resistant as they mature.

Fig. 5 Infection of downy mildew on young cluster and shoot showing curling and thickening of diseased tissue (Chancellor). The white sporulation after a warm humid night can be striking.

 

Fig. 6 Berries of red varieties (Concord (left) and Chancellor (center) at harvest) often turn red or pink after infection and fail to soften and develop properly. Late season leaf infections (far right photo) are yellowish to reddish brown and appear angular or blocky.

Cultural and chemical control:

Because the first inoculum arises from the vineyard soil, cultivation in early spring can help to bury over-wintering inoculum in old leaves and clusters on the ground, reducing primary inoculum in spring (much like with black rot). The first infections in spring often occur on shoots and sucker growth near or on the ground, and prompt elimination of this tissue can delay the occurrence of the first infections in the canopy. Also, the maintenance of an open canopy, where fruit and other susceptible tissue dry out as quickly as possible after rainfall and dew, will help minimize disease development.

There are many chemical options for downy mildew control and the best materials should be applied around and shortly after bloom. Active ingredients found in Ridomil, Zampro, Presidio, and Revus (and Revus Top) have been most effective on downy mildew in our trials. Where strobilurins are still working on this disease (no resistance yet), Abound (except in Erie county), Pristine, and Reason have been very effective too. The phosphorus acid formulations like Phostrol, Prophyt, and Rampart to name a few, have also been very effective against downy mildew, but generally cannot be expected to provide good control beyond 10 days after application, especially under high disease pressure. A tank mix of Ranman (cyazofamid) and phosphorus acid has been shown to be very effective on downy mildew in many university trials. All these aforementioned materials are very rainfast. In addition to these fungicides are the old standards that are strictly surface protectants and are more subject to removal by rainfall. A mancozeb product is probably the best among this group, but fixed copper fungicides can also be quite effective against downy mildew on varieties that are not sensitive to copper. Ziram and captan can also be part of an effective downy mildew program, but are somewhat less effective than mancozeb.

Powdery mildew is caused by the fungus Uncinula necator.  Infection on leaves appears mainly on the upper surface as white, powdery patches, though the undersides of leaves can also become infected (Figure 7). As the leaf surface becomes covered with the fungus, leaf function (and photosynthesis) is impaired, with varieties of V. vinifera and highly susceptible French hybrids being most severely affected. Infection by U. necator can stunt growth of new tissues and severe infection of young expanding leaves often results in cupping and distortion of leaves. Cluster infections around bloom may lead to poor fruit set, while later infection can cause berry splitting.

Fig. 7 Powdery mildew on young, developing ‘Concord’ berries.

Though primary infections in spring (at least 0.1″ rainfall and greater than 50 F) require rainfall for spore release, secondary disease cycles that result from primary infections, do not require rainfall.  Under optimum weather conditions (temperatures in the mid 60s to mid 80s F) secondary disease cycles can be repeated every 5 to 7 days, allowing for explosive increase of disease in the vineyard, especially in highly susceptible wine varieties. Note that optimum temperatures for the fungus are the norm through most of the summer in Pennsylvania and that starting around bloom, nearly every day is an infection period, rain or shine.

In most grape varieties, berries are highly susceptible to infection from the immediate pre-bloom stage until about 2-3 weeks after fruit set, and efforts to protect fruit with fungicides should concentrate on this critical period with timely applications every 7-14 days. Cluster rachises and leaves remain susceptible until harvest and their need for continued protection depends on varietal susceptibility, crop size, and weather. For example, after the fruit susceptibility period, further management of leaf and rachis infections may not be necessary on Concord and other native juice varieties unless vines are heavily cropped or ripening conditions are poor.  On the other hand, V. vinifera and susceptible hybrids, may require management of foliar mildew until at least veraison or beyond.

Cultural and chemical control:

There are cultural considerations that can reduce opportunities for powdery mildew disease development.  Most involve limiting humidity and promoting sun exposure to all parts of the vine. For example, a training system that improves air movement through the canopy, prevents excess shading and humidity and promotes fungicide penetration to the cluster zone which will help reduce powdery mildew development. Sunlight is lethal to powdery mildew and regular exposure of leaves and fruit can greatly reduce mildew development. Good weed control can also minimize humidity levels that contribute to mildew development.

Unfortunately, cultural measures can only serve as an enhancement to a chemical control program in Pennsylvania and other parts of the northeast. However, we have many effective fungicides for powdery mildew that can provide high levels of control through the critical period around bloom: Vivando, Quintec, Luna Experience, Endura, and now Aprovia. Aprovia is also labeled for black rot control, but our recent tests have indicated that Aprovia’s black rot efficacy is limited especially under high disease pressure on susceptible varieties. The difenoconazole products (Revus Top, Quadris Top, Inspire Super) can also be very effective on powdery mildew, though they may best be used outside the critical two spray period around bloom. Be aware that difenoconazole has been found to cause injury to Concord and a few other varieties (read the label). Sulfur can be an effective powdery mildew material too (on sulfur tolerant varieties) and many wine grape growers rely heavily on it, especially as a tank mix pre-bloom with mancozeb for all diseases. However, it is not recommended as a ‘stand-alone’ material during the critical fruit protection period for powdery mildew control.

There are lots of ‘alternatives’ for powdery mildew control that may be appropriate for late season sprays (to maintain a clean vineyard) that may gradually be used to replace the sulfur and/or synthetics or rotate with synthetics, particularly for reds where late sulfur applications can create wine quality issues. These are materials for which there is little risk of the development of resistance. In fact, these materials can be used to manage the development of resistance to our more risky synthetic fungicides mentioned earlier. Petroleum based oils like JMS Stylet-oil are very effective at 1-2 % solution, but excessive use late in the season (do not apply around or after veraison) may limit sugar accumulation and fruit maturity.  And, oils should not be tank mixed with sulfur or applied within 14 days of a sulfur-containing fungicide application. Copper, is moderately effective on powdery mildew and generally applied with lime to reduce the risk of phytotoxicity (read the label). Like sulfur, copper fungicides should not be applied under slow drying conditions as this increases the chance for plant injury. Other materials include potassium bicarbonates such as Kaligreen, Armicarb O, and Milstop.  These materials generally produce modest results, and are most effectively applied at short intervals (7 days) to achieve satisfactory control on susceptible varieties.  Again, these materials are not appropriate for the critical fruit protection period, but are best integrated during the early season when disease pressure is low OR after the critical fruit protection period to help control leaf infections.

Phomopsis cane and leaf spot is caused by the fungus, Phomopsis viticola. Earlier this spring, growers in many parts of Pennsylvania experienced problems with Phomopsis development on new shoots and leaves. Prolonged wetting/rainfall during the first week of May led to widespread infection by this pathogen on Concord in the Lake Erie region; virtually every shoot of every vine in every Concord vineyard we have examined has some level of Phomopsis development on the first one or two internodes. The infection period(s) occurred when shoots were in the 1-3″ range and inflorescences were just becoming exposed. In some cases, heavy infection of inflorescences is likely to result in problems with fruit rot after veraison (months after the infection period took place!). Fruit are generally at risk of new infections until a couple weeks or so after bloom, but infections of the cluster stem tissue that occur in the early pre-bloom period can move into berries during ripening and cause fruit to rot and shell before harvest. The concentration of heavy infection at the base of the oldest internodes, may result in large scabby areas that weaken the shoot (Figure 8) and green shoots that are severely infected are more apt to break under windy conditions. Leaf infections appear as pinhead sized black spots surrounded by a yellow halo (Figure 9). These infections appear to be of little consequence, other than revealing the presence of the pathogen. Lesions on cluster stems are black and sunken, and can girdle parts of the cluster rachis causing the cluster or parts of the cluster to break off or shrivel.

Fig. 8 Numerous lesions concentrated at the base of the oldest internodes result in larger scabby areas that weaken the shoot.

 

Fig. 9 Leaf infections of Phomopsis cane and leaf spot on Concord grape.

When berries are infected, they can remain symptomless until ripening when they turn brown and become studded with small pimple-like fruiting structures of the fungus (Figure 10) often resembling black rot infected berries.

Fig. 10 Phomopsis fruit rot on ripe Vignoles and Niagara grapes.

However, even though direct fruit infection by both pathogens can occur during the same peak susceptibility period (bloom through 3-4 weeks after bloom), black rot fruit rot symptoms become observable while berries are still green, whereas Phomopsis fruit infections lay dormant until after ripening. Also, leaf symptoms of these two diseases are very different from each other and can be used to determine which pathogen(s) are present and most likely to have caused disease on nearby fruit.

Cultural and chemical control:

Hand pruning to remove dead wood and pruning stubs from the trellis removes much of the over-wintering inoculum of Phomopsis. For this reason, cane pruning can reduce the disease compared to a cordon system that retains a maximum amount of older wood. Trellis systems that train shoots upward also reduce infections on the oldest shoot internodes and clusters. And of course, the maintenance of an open canopy where fruit and other susceptible tissue dry out as quickly as possible after rainfall, will help minimize disease development.  For wine grapes, fruit zone leaf removal and shoot thinning reduce canopy density, hasten drying after rainfall, and improve fungicide penetration and coverage of the fruit.

Phomopsis management with fungicides should continue through the first or second post bloom spray, after which inoculum of the fungus is generally spent. Strobilurins, mancozeb products, Captan, and Ziram are generally the only effective materials for Phomopsis control. Some formulations of sterol inhibitor fungicides claim Phomopsis control, but their level of efficacy is still under question and would not be recommended for management of this disease.

 

Much of the information in this blog can be found in the 2017 New York and Pennsylvania Pest Management Guidelines for Grapes. Be sure to get your copy through Cornell University press. You can also read the publication; Disease Management Guidelines for Organic Grape Production in the Lake Erie Region found online at http://agsci.psu.edu/research/ag-experiment-station/erie/research/plant-pathology/organic-grape-disease-management-trials/DiseaseMgmtGuidelines07.pdf which contains much of the information discussed in this blog.

 

References:

2017 New York and Pennsylvania Pest Management Guidelines for Grapes. Edited by Tim Weigle and Andy Muza. Cornell and Penn State University Cooperative Extension.

Hoffman, L.E., W.F. Wilcox, D.M. Gadoury and R.C. Seem. 2002. Influence of grape berry age and susceptibility to Guignardia bidwellii and its incubation period length. Phytopathology 92:1068-1076.

Hoffman, L.E., W.F. Wilcox, D.M. Gadoury, R.C. Seem, and D.G. Riegel. 2004. Integrated control of grape black rot: Influence of host phenology, inoculum availability, sanitation, and spray timing. Phytopathology 94: 641-650.

Grape Leafhoppers

By: Andy Muza, Penn State Extension – Erie County

There are several species of leafhoppers in the genus Erythroneura that feed on grape foliage. Research conducted in New York showed that the eastern grape leafhopper Erythroneura comes (Say) is the most common on American varieties (e.g., Concord, Niagara) while E. bistrata/vitifex complex were more common on Vitis vinifera and interspecific hybrids. Other species found in commercial grapes included E. tricinta, E. vulnerata and E. vitis. (1). Regardless of which of these species is prevalent, their life cycles are similar and the injury caused by these leafhoppers and their management is the same.

Life Cycle and Description

The various Erythroneura leafhoppers overwinter as adults in leaf litter in the vineyard or in plant debris around the vineyard. As temperatures increase in the spring, adults begin feeding on a variety of weeds, bushes and trees. Adults then migrate into vineyards to feed when leaves emerge (2). Eastern grape leafhopper adults are small (only about 1/8”), white-pale yellow, with darker lemon colored markings on the wings, and 3 black spots towards the posterior portion of the wings (Figures 1 & 2).  Other Erythroneura species have varying coloration and markings (3).

 

Figure 2. Adult grape leafhoppers on underside of Concord leaf. Photo: Andy Muza, Penn State.

Initial feeding occurs on sucker growth and basal leaves on shoots in the trellis. Females lay eggs on the undersides of leaves just below the leaf surface. Nymphs of the first generation hatch in mid-late June. Immatures are wingless, pale yellow in coloration with tiny wing pads (Figure 3). Nymphs develop through 5 instars with wings fully developed after the fifth molt (2). Nymphal development to adulthood takes about 30 days or less depending on environmental conditions. In northwestern Pennsylvania nymphs of the second generation can be found in vineyards in mid-late August. There are 1.5 – 2 generations/season in the Lake Erie Region, depending on seasonal temperatures, and in the southwestern portion of the state likely 2.5 – 3 generations.

Grape leafhopper (GLH) adults and nymphs have piercing – sucking type mouthparts and feed on the underside of leaves extracting the contents of leaf cells resulting in white – yellow spotting of the foliage (stippling). Moderate – Heavy feeding causes yellowing and browning of tissue while severe injury can result in premature defoliation (Figure 4).

Figure 4. Concord leaf with stippling and browning of leaf tissue caused by GLH feeding. Photo: Andy Muza, Penn State.

Management

The greatest risk for economic losses due to grape leafhopper (GLH) feeding occurs during hot, dry years in vineyards with heavy crop loads and high leafhopper populations (4). In most years, the majority of vineyards in Pennsylvania should not require an insecticide treatment specifically for management of grape leafhopper. Therefore, routine, prophylactic insecticide treatments for leafhoppers are unnecessary and not recommended. Insecticide applications should be based on scouting information and threshold levels.

Scouting – Tim Martinson at Cornell designed a scouting procedure for leafhoppers which corresponds to the timings when sampling for grape berry moth injury are conducted (5).

10 Days Postbloom – Usually population levels and feeding is minimal at this time of the season. If however, early in the season, high numbers of adult leafhoppers migrate into the vineyard this can result in enough leaf feeding to reduce bud fruitfulness in the following year (4). Scouting should be conducted to look for leaf feeding on interior leaves in the canopy. If leaf stippling is noticeable throughout the vineyard then an insecticide application is recommended.

Third week in July – Check 4 different areas in the vineyard (2 exterior and 2 interior). At each area look at lower leaves on shoots and check for leaf feeding. If no – minimal injury is observed, proceed to the next sampling site (Figure 5). If moderate-heavy leaf stippling is observed then begin counting nymphs on the undersides of leaves (Figure 6). Examine 5 leaves (leaves 3-7 from base of shoot)/shoot on 5 different shoots at each location. If a threshold of 5 nymphs/leaf is reached then an insecticide application is recommended.

Figure 5. Minimal GLH stippling on Concord leaf. Photo: Andy Muza, Penn State.

 

Figure 6. GLH nymphs, cast nymphal skins and adults on underside of leaf. Photo: https://ecommons.cornell.edu/bitstream/handle/1813/43102/grape-leafhopper-FS-NYSIPM.pdf?sequence=1&isAllowed=y

Late August – The scouting protocol at this time follows the same procedure as the July sampling. However, the threshold for the August sampling period is 10 nymphs/leaf before an insecticide application is recommended.

Based on scouting data, if an insecticide application becomes necessary during the season, there are a number of options available. Consult the “2017 New York and Pennsylvania Pest Management Guidelines for Grapes” (6) for a list of insecticides which are effective for grape leafhopper management.

Shoot and leaf removal practices conducted in many wine grape vineyards may reduce leafhopper population levels, if the removed leaves are harboring nymphs of this pest. In addition, these practices will open up the canopy for better spray penetration.

A number of predators (e.g., spiders, green lacewings, lady beetles, etc.) and egg parasitoids (Anagrus species) which occur in vineyards contribute to reducing leafhopper population levels (7). Therefore conserving these beneficial insects, by avoiding unnecessary applications of broad spectrum contact insecticides, is advised. Good weed control in the vineyard and the prevention of overgrown areas around the vineyard will also reduce leafhopper overwintering sites.

References

  1. Martinson, T. E. and T. J. Dennehy. Varietal Preferences of Erythroneura Leafhoppers (Homoptera: Cicadellidae) Feeding on Grapes in New York. Environ. Entomol. 24:550-558 (1995). https://academic.oup.com/ee/article/24/3/550/2394852/Varietal-Preferences-of-Erythroneura-Leafhoppers
  2. Grape Leafhopper. Grape Insect IPM Insect Identification Sheet No. 4 (1984). NYS. Ag. Exp. Station, Cornell University. https://ecommons.cornell.edu/bitstream/handle/1813/43102/grape-leafhopper-FS-NYSIPM.pdf?sequence=1&isAllowed=y
  3. Leaf- Stippling Leafhoppers (Ontario GrapeIPM). Ontario Ministry of Agriculture Food & Rural Affairs, Canada http://www.omafra.gov.on.ca/IPM/english/grapes/insects/ls-leafhoppers.html
  4. Martinson, T. E., et al. Impact of Feeding Injury by Eastern Grape Leafhopper (Homoptera:Cicadellidae) on Yield and Juice Quality of Concord Grape. Am. J. Enol. Vitic., 48:291-302 (1997). http://www.ajevonline.org/content/ajev/48/3/291.full.pdf
  5. Martinson, T. E., et al. Risk Assessment of Grape Berry Moth and Guidelines for Management of the Eastern Grape Leafhopper. New York’s Food and Life Sci. Bull. 138. 10 pp. (1991). http://nysipm.cornell.edu/publications/grapeman/files/risk.pdf
  6. Weigle, T. H., and A. J. Muza. 2017. “2017 New York and Pennsylvania Pest Management Guidelines for Grapes”. Cornell and Penn State Extension. 150 pp. https://store.cornell.edu/p-197039-2017-new-york-and-pennsylvania-pest-management-guidelines-for-grapes.aspx
  7. Williams, L., III, and T. E. Martinson. 2000. Colonization of New York Vineyards by Anagrus spp. (Hymenoptera:Mymaridae): Overwintering Biology, Within-Vineyard Distribution of Wasps, and Parasitism of Grape Leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), Eggs. Biol. Control 18:136-146.   https://pubag.nal.usda.gov/pubag/downloadPDF.xhtml?id=43140&content=PDF

Early season grapevine canopy management, Part II: Early leaf removal (ELR)

By:  Maria Smith and Dr. Michela Centinari, Dept. of Plant Science

In the previous post, we discussed shoot thinning as a method to achieve vine balance and improve the canopy microclimate (Part I: Shoot Thinning). In this post, we will discuss the use early leaf removal (ELR), a canopy management practice implemented around bloom.  ELR primarily serves to reduce the severity of Botrytis bunch rot infection in susceptible varieties (Wines and Vines:  Benefits and Costs of Early Leaf Removal), but may also be an effective practice for reducing crop yield.

ELR is currently considered an experimental canopy management practice for vineyards.  While it shows great promise within the research and Extension literature (1, 2, Cornell Cooperative Extension 2016), Penn State Extension does not currently recommend implementing ELR as a replacement for traditional methods (i.e., cluster thinning, fungicide sprays) for yield and rot control. However, growers curious about the effects of ELR may find it useful as a supplementary canopy management practice, especially for disease management and crop reduction.

Throughout this post, we will discuss the effects of ELR on:

  • Crop level in highly-fruitful varieties that produce a high number of clusters (3-4 per shoot) or large clusters such as vinifera cvs. Grüner Veltliner, Sangiovese, and Barbera.
  • Botrytis bunch rot infection.
  • Fruit and wine composition.

What is Early Leaf Removal (ELR) and how does it work?

ELR is the removal of basal leaves of the main shoots and, optionally, lateral shoots developed from the basal nodes (http://gph.is/2r3ZLc0; Figure 1).

Screenshot 2017-06-01 12.31.36

ELR is typically performed shortly before (pre-bloom) or at the beginning of bloom (trace-bloom; Figure 2A). In some cases, however, it has been performed later during full-bloom or at the onset of fruit-set (Figure 2B).

Screenshot 2017-06-01 12.31.48

Before and during bloom, the oldest basal leaves have a major role in providing carbohydrates (e.g., sugars) to support the growing shoot and inflorescence (i.e., flower clusters). In contrast, young leaves on the middle and top part of the shoot are still developing and not very photosynthetically ‘active’ at this time (3).  Literature suggests the removal of basal leaves at bloom may starve the inflorescence for a carbohydrates food source (4).  The lack of carbohydrate resources reduces fruit-set (i.e., the percentage of flowers that will develop into berries), which likely reduces the number of berries per cluster at harvest (5). When ELR is performed later, at the onset of fruit-set, removing basal leaves may induce a reduction in berry size and an increase in berry abscission due to carbohydrate limitation at the onset of fruit development (6). Therefore, yield reduction achieved with ELR is the result of reduced cluster weight (reduced number of berries per cluster and/or reduced berry weight). In contrast, yield reduction achieved by cluster thinning is the result of a reduced number of clusters per vine.

Why are ELR practices currently under research investigation?

An increased number of studies is investigating the use of ELR as a potential alternative to cluster thinning techniques used for crop yield control in highly-fruitful wine grape varieties (5, 6, 7). As opposed to traditional cluster thinning, ELR can be more easily mechanized. (Author’s note:  for more information on mechanization, see Additional Resources at the bottom of the post.) ELR may additionally confer benefits such as:

  1. Reduced severity of Botrytis rot infection

Cluster compactness, or the tightness of berries on the cluster, has been positively related to the severity of Botrytis bunch rot infections (8). It is suggested that more compact clusters experience more rot. ELR decreases cluster compactness by reducing the number of berries per cluster and/or the berry size. Decreased cluster compactness through implementing ELR has reduced Botrytis rot infections in several tight-cluster varieties such as Pinot Noir, Riesling, Chardonnay, and Vignoles (1, 9, 10, 14). As an additional benefit, the removal of basal leaves increases sunlight penetration and air movement in the fruiting zone, which is important for improving spray penetration within the canopy (2016 Post Bloom Disease Management Review).

  1. Improved fruit and wine composition

ELR has consistently been reported to alter fruit composition, particularly for red Vitis vinifera varieties in Mediterranean climates (Tempranillo, Sangiovese, Barbera, etc.; 2, 5, 6, 12). In several instances, fruit harvested from ELR vines had higher levels of total soluble solids (TSS, °Brix), phenolic compounds (e.g., flavonols), and total anthocyanins compared to un-defoliated vines (2, 11, 12). ELR can also reduce methoxypyrazines, ‘herbaceous’ aromas found in higher concentrations among immature grapes at harvest, and may contribute to improved wine color intensity (13).  ELR may alter three important parameters associated with berry development and ripening (2):

  • Decreased berry size – Smaller berries tend to have greater skin-to-pulp ratio and higher concentrations of desirable phenolic and aroma compounds which are mainly present in the skin.
  • Increased leaf area-to-yield ratio on a per shoot basis – A greater leaf area-to-yield ratio may translate into higher sugar produced per shoot. More sugar availability could contribute to better fruit ripening.
  • Improved canopy microclimate – ELR, like traditional leaf removal, improves the microclimate of the fruiting zone through decreased leaf density and increased sunlight penetration to the fruit. Higher temperatures coupled with increased sunlight exposure in the fruiting zone can be especially important under cool or cloudy ripening conditions, as they may accelerate berry ripening, resulting in higher TSS, decreased malic acid, increased anthocyanin concentration, and degradation of green volatile aroma compounds such as methoxypyrazines that may mask fruity or floral aromas. Higher ultraviolet (UV) radiation in the fruiting zone in response to increased sunlight penetration may increase production of flavonols, as flavonols biologically act to protect berries from UV exposure (3, 11). Flavonol compounds along with anthocyanin influence red wine color and are used as determinants of quality in fruit (11).

It is important to keep in mind that yield reduction is not desirable in all grape varieties. The use of ELR with varieties that do not typically over-crop may result in under-cropped situations with potential negative effects on fruit quality and vine health, in addition to unnecessary yield reductions and thus revenue loss.

How many leaves should be removed to induce yield reduction?

Unfortunately, there is no “one size fits all” number of leaves to remove when implementing ELR as a vineyard management practice.  The required number of leaves removed to significantly reduce yield through reduced fruit-set depends on several factors, including shoot length and the shoot leaf area at the time of removal. For example, by pulling 5 basal leaves on a shoot with only 8 leaves at trace-bloom, we would remove about 63% of the total number of leaves.  The percentage of leaf area removed would be even higher as the remaining leaves at the top of the shoot are much smaller than those removed from the bottom of the shoot. In contrast, a longer shoot with 15 leaves total will only lose 33% of the leaf area when 5 basal leaves are pulled. Thus, removing 5 leaves from a short shoot would have a more severe effect of depriving the inflorescence of sugar resources than removing the same number of leaves on long shoots (Figure 3).

Screenshot 2017-06-01 12.32.01

Sometimes the degree of ELR is severe in order to induce a yield reduction commensurate with the more traditional cluster thinning technique. For example, Pinot Noir grown in southwestern Michigan showed a reduction in yield from 6.1 tons per acre in non-defoliated vines to 3.6 tons per acre when about half (8 out of 15) of the leaves on the shoots were removed (1). This was a 40% reduction in yield. Comparatively, when 4 or 6 leaves were removed from the Pinot Noir, no significant effect was found in crop yield (1).

With the high potential for crop yield reduction, Dr. Michela Centinari’s lab has been experimenting with ELR for the past two years. We have been examining the effects of ELR at trace-bloom on Grüner Veltliner (V. vinifera) grown in Central Pennsylvania. Grüner Veltliner is highly fruitful, typically producing 2-3 large clusters per shoot. In our experimental practices, we removed 5 basal leaves at trace-bloom. Our objective was to compare the use of ELR to cluster thinning for crop yield reduction. Our first year of data found that the implementation of ELR decreased yields by only about 15% (10.7 tons per acre in the non-defoliated control to 9.3 tons per acre in defoliated vines). In comparison, vines thinned to 1 cluster per shoot had a 45-50% reduction in yield compared to the un-thinned control (10.7 tons per acre to 6.5 tons per acre).

This suggests that a greater leaf removal intensity may be needed for this variety to produce yield reduction comparable to cluster thinning, and we are currently testing different intensity levels of trace-bloom ELR to evaluate if the amount of leaf area removed correlates with reduction of fruit-set and yield at harvest.

Again, ELR is still considered an experimental canopy management technique. For those growers growing high yielding varieties and looking to reduce crop level, cluster thinning is still the recommended practice. For more information on how to implement appropriate CT techniques, please see Cornell Cooperative Extension Fruit thinning in wine grapes and Crop thinning: cluster thinning or cluster removal.

Considerations regarding ELR

Other factors to consider if you are interested in applying ELR:

  • Fruit-set percentage – One of the factors facing the unpredictability of ELR is the weather conditions between bloom and fruit set. Since weather can have a large effect on the percentage of fruit-set (Fruit set in grapes 101), ELR may potentially exacerbate ‘poor’ fruit-set if extended periods of wet, cool (< 59°F), overcast, or very hot (> 90°F) weather conditions occur following leaf removal.  Additionally, berry sunburn may be a potential concern with ELR when performed under chronic high light and temperature intensity.
  • Bud Fruitfulness – While it is generally acknowledged that increased sunlight exposure is positive for bud development, a potential reduction in bud fruitfulness (number of clusters per shoot) may occur in the following season as a result of bud damage from ELR (14). Although still uncertain, bud damage may be the result of physical damage during leaf removal and/or reduction of carbohydrate supply during bud development.
  • Carbohydrate Storage in Cool Climate Grown Vines – Carbohydrates are the main energy source for grapevine growth, stress defense, and fruit ripening. Post-harvest carbohydrate storage in perennial tissues is a determinant of vine overwinter survival and is fundamental for shoot development in the following season. Removing leaves during ELR may alter the amount of carbohydrates produced by the leaves over the season and how carbohydrates are distributed among the vine organs. Currently, limited information is available on how ELR affects carbohydrates storage in perennial tissues and how this relates to dormant tissue (buds and canes) cold hardiness. This is a point of current interest to Centinari’s lab at Penn State, with current research being conducted in vinifera and hybrid wine grape varieties.
  • Crop Estimation – Yield predictions based on ELR use is currently not available. In this regard cluster thinning is a more conservative approach. Unlike ELR, which is performed very early in the season, cluster thinning severity can be decided upon estimation of final yield.

 

Summary

ELR holds potential as a way to reduce yield and Botrytis rot infection for some grape varieties grown in the Mid-Atlantic and other cool-climate regions. However, more research is needed to better understand the consistency of ELR practices on vine physiology, yield reductions, and fruit quality. Current efforts are on-going by the Centinari lab and Bryan Hed at the Lake Erie Grape Regional Extension Center (LEGREC) to evaluate the use of manual and mechanized ELR in hybrid and V. vinifera varieties across Pennsylvania.

Additional Resources

PSU Wines and Grapes blogs:  An Overview of Cluster-Zone Leaf Removal Strategies for Cool Climate Vineyards and 2016 Post Bloom Disease Management Review

Intrieri C, Filippetti I, Allegro G, et al. 2008.  Early defoliation (hand vs mechanical) for improved crop control and grape composition in Sangiovese (Vitis vinifera L.).  Aus. J. Grape Wine Res. doi: 10.1111/j.755-0238.2008.00004.x

References Cited

  1. Acimovic D, Tozzini L, Green A, et al. 2017. Identification of a defoliation severity threshold for changing fruitset, bunch morphology and fruit composition in Pinot Noir.  J. Grape Wine Res. doi:  10.1111/ajgw.12235
  2. Bubola M, Sivilotti P, Janjanin D, and Poni S.   Early leaf removal has larger effect than cluster thinning on cv. Teran grape phenolic composition.  AJEV.  doi: 10.5344/ajev.2016.16071
  3. Illand P, Dry P, Proffit P, and Tyerman S. Photosynthesis. In The Grapevine, from the science to the practice of growing vines for wine. pp. 91-107.
  4. Coombe BG.   The effect of removing leaves, flowers and shoot tips on fruit-set in Vitis vinifera L. J. Hortic. Sci. 37:1-15.
  5. Poni S, Casalini L, Bernizzoni F, et al. 2006. Effects of early defoliation on shoot photosynthesis, yield components, and grape composition. AJEV. 57: 397-407.
  6. Tardaguila J, Martinez de Toda F, Poni S, and Diago MP. 2010. Impact of early leaf removal on yield and fruit and wine composition of Vitis vinifera Graciano and Carignan. AJEV. 61(3):372-381.
  7. Silvestroni O, Lanari V, Lattanzi T, et al. Impact of crop control strategies on performance of high-yielding Sangiovese grapevines. AJEV. doi: 10.5344/ajev.2016.15093
  8. Vail ME and JJ Marois. 1991. Grape cluster architecture and the susceptibility of berries to Botrytis cinerea. Phytopathology 81:188-191.
  9. Sternad Lemut M, Sivilotti P, Butinar L, et al. Pre-flowering leaf removal alters grape microbial population and offers good potential for a more sustainable and cost-effective management of a Pinot Noir vineyard. J. Grape Wine Res. doi: 10.1111/ajgw.12148
  10. Hed B, Ngugi HK, and Travis JW.   Short- and long-term effects of leaf removal and gibberellin on Chardonnay grapes in the Lake Erie region of Pennsylvania. AJEV.  66(1): 22-29.
  11. Moreno D, Vilanova M, Gamero E, et al. Effects of preflowering leaf removal on phenolic composition of Tempranillo cv. in semi-arid terroir of western Spain.  AJEV. doi: 10.5344/ajev.2014.14087
  12. Risco D, Pérez D, Yeves A, et al. Early defoliation in a temperate warm and semi-arid Tempranillo vineyard: vine performance and grape composition. Aus J Grape and Wine Res. doi: 10.1111/ajgw.12049
  13. Sivilotti P, Herrera JC, Lisjak K, et al. 2016. Impact of leaf removal, applied before and after flowering, on anthocyanin, tannin, and methoxypyrazine concentrations in ‘Merlot’ (Vitis vinifera) grapes and wines. J. Agric. Food Chem.  64:4487-4496.
  14. Sabbatini P, and Howell GS. 2010. Effects of early defoliation on yield, fruit composition, and harvest season cluster rot complex of grapevines.  HortScience 45(12):1804-1808.

Maria Smith is a viticulture PhD candidate with Dr. Michela Centinari in the Department of Plant Science.  She specializes in cold stress physiology of wine grapes.  She was the previous recipient of 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.  She is currently funded by the Northeast Sustainable Agriculture Research and Education (NE-SARE) program, a program from the USDA National Institute of Food and Agriculture (NIFA).

 

An American (Wine Marketer) in Paris

By Dr. Kathy Kelley

I have been fortunate over the past few years to co-lead groups of Penn State undergraduates on a two-week experience in Paris, France, with the goal of comparing U.S. and French agriculture and food systems.  The students learn about U.S. systems from Penn State experts during the spring semester and then they learn about the French systems when abroad in mid-May.   Grape and wine production happens to be one of the topics they study, and they get an opportunity to not only visit a vineyard and winery in Pennsylvania but a couple of operations in the Champagne region.  On my time off I visit wine shops and look for wine-related “things” that may be of interest to you, our blog readers.  What follows is a bit of what I have seen so far on my trip.

Learning about Wine in High School

One of the stops we took the Penn State students to in the Champagne region was an agricultural high school (Lycée Agroviticole – Crézancy; http://bit.ly/2qyL40l).  The school was founded in 1870 and is just one of several schools that teach students about farm management.   Some of the students who have an interest in becoming winemakers, along with high school graduates who seek viticulture and enology training, are responsible for the vineyards and grow the three main wine grapes used to make Champagne (Chardonnay, Pinot Noir, and Pinot Meunier). Screenshot 2017-05-19 16.23.55

In addition to learning about grape production, the students also learn the multi-step process of making Champagne and are involved in all steps of the process.

Screenshot 2017-05-25 19.16.35

Screenshot 2017-05-25 08.40.05Under the direction of a cellar master, the students’ final product is labeled and available for purchase.  Selections, with the price in U.S. dollars, include Brut Tradition ($15.00), Brut Blanc de Blanc ($16.30), Brut Rose ($16.75), Demi-Sec Tradition ($15.73), and Euphrasie Millesime 2008 ($21.35) (http://bit.ly/2rljEMQ). A product that is now available, but was not in 2015 when I last visited with a group, is Brut Terroir – their organic option ($19.11).

Champagne can be purchased online as well as from the cellar at the school.  A building is currently being converted into a retail space that the students will operate.  Students interested in Champagne production also attend conferences, participate in judging events, and co-host events for the industry.

Screenshot 2017-05-25 08.39.40

A 20,000 Euro ($22,474.74) Bottle of Wine

I am drawn to retail establishments and really enjoy observing how products are displayed, how the space is used, and the overall “feel” of the store.  While Paris has many wine shops and places to buy wine (even a wine shop where no French wine is sold/served (http://soifdailleurs.com), I enjoy visiting La Cava at the Lafayette Gourmet near the Opera Garnier in the 9th Arrondissement (http://bit.ly/2rkwriQ) because it is in the midst of a supermarket in the basement of a department store and it is staged as if it were a museum.  It is roomy, security guards are staged at the entrances, and the lighting highlights certain pieces (wines).

Screenshot 2017-05-25 13.52.35

There are approximately 2,500 labels, of which almost half are from Bordeaux.  Each time I visit I look for the most expensive wine available for purchase.  Though I found a few bottles that were priced over 2,000 euro (approx. $2,250 U.S.), I also found a few 750 mL bottles that were just a bit more: a 1945 Chateau Latour (Bordeaux), which Parker awarded a 90/100 and Wine Spectator a 100/100 (http://bit.ly/2rTOKs6), that sells for 12,900 euros (approx. $14,500 U.S.) and an 1899 Chateau d’Yquem (Bordeaux) for 20,000 euros (approx. $22,500), which Wine Spectator awarded a 91/100 (http://bit.ly/2qjseYs).   However, if those prices seem a little steep, do not forget that you can request a VAT tax refund when you leave the country, which for the Chateau d’Yquem is 2,400 euros (approx. $26,900 U.S.).

Screenshot 2017-05-25 14.30.35

Lavinia

Another shop that I visit when in Paris is Lavinia (located in the 1st Arrondissement, http://bit.ly/2qnVah7).  The business was established in 1999, has over 6,500 labels (including selections from the U.S.), and is often referred to as the Europe’s largest wine store.

Screenshot 2017-05-25 17.27.37

“La Cave” is in the basement level and houses rare and expensive wines.  In order to access the wines in this section, you will need to ask a staff member to open the door with a code, after which they will accompany you while you make your selection, and then they will bring the bottle to the cashier.  This is the one section of the store where it is forbidden to take photos of the bottles in an effort to minimize any exposure to excessive light from a camera’s flash.

After walking around both floors you may be interested in having a meal in the restaurant.  If you are interested in learning what wines pair with items on the menu you need only look at the display outside the dining room, find the particular food item (e.g., salad, cheese, a specific entrée), and refer to what wines are positioned in the column under the photo.  If you would like to taste a particular wine, ask for a card (deposit of 3 euros), load 10 euros or more onto the card, and insert it into one of four machines that will dispense a select number of reds, rose, or white wines, all for 1.10 euro to 9.60 euro per 3 cl (1 fluid ounce).

Screenshot 2017-05-25 17.25.58

As you can imagine with a city the size of Paris – the number of options for getting a glass or bottle of wine is immense.  If Paris is on your list of places to see, or if it is time for you to visit again, be sure to investigate what bars, restaurants, shops, and tastings you would like to experience.  While many establishments are well known and marked there are also a number of speakeasies in the city that deserve a visit, one of which is Lavomatic (https://www.lavomatic.paris).

Lavomatic is a working laundry mat with a secret door hidden behind one of the dryers.  After you push the “start” button on the dryer and pull the door to open it- you will find a dark staircase that leads up to a small bar with a few small seating areas including a few swings that hang from the ceiling.

Screenshot 2017-05-25 19.05.08Screenshot 2017-05-25 19.01.42

Until next time…

Early season grapevine canopy management, Part I: Shoot thinning

By: Maria Smith and Dr. Michela Centinari, Dept. of Plant Science

This is the first of two posts on grapevine canopy management in the early growing season from bud burst to bloom.  The second in the series will be post in two weeks and will focus on pre- or trace-bloom leaf removal for crop level and disease pressure control.

This week, our blog post will focus on shoot thinning, the first canopy management practice of the growing season.  As seen in the pictures below, we spent last week shoot thinning Grüner Veltliner (V. vinifera) vines in a central Pennsylvania vineyard (Figure 1).

Figure 1. (A) Andrew Harner, graduate student at Penn State in the Centinari lab, is shoot thinning Grüner Veltliner (V. vinifera) vines, May 10, 2017, Lewisburg, PA. (B) Grüner Veltliner shoot length at the time of thinning (pencil as a reference for shoot length).

In the following sections, we will highlight the benefits and costs associated with shoot thinning while providing a few general shoot thinning guidelines for both V. vinifera and hybrid cultivars in the Mid-Atlantic region.

Benefits of Shoot Thinning Grapevines

While dormant pruning (https://psuwineandgrapes.wordpress.com/tag/dormant-pruning/) is the primary tool used by grape growers to maintain vine structure, canopy architecture and regulate crop level, shoot thinning provides an additional canopy management tool to bring vines into vegetative and fruiting balance by reducing shoot density and the number of clusters per vine. Cluster thinning later in the season may be needed in order to balance highly-fruitful vines.

In addition to improving balance between vegetative growth and fruit biomass, other benefits of shoot thinning include:

  • Reduction of canopy density and fruit shading: through removal of selected shoots, shoot thinning reduces overcrowding of shoots in the canopy thus reducing the number of leaf layers and improving sunlight exposure to fruit (1).
  • Reduction of disease pressure: reducing canopy density improves air circulation and sunlight penetration that promotes quicker drying of leaves and fruit, as well as increases spray penetration.

Timing of Shoot Thinning

Shoot thinning should be done early in the growing season, when shoots are approximately 5-6 inches long and not more than 10-12 inches long. Shoot thinning should be timed after the date of last ‘expected’ frost, such that secondary or non-damaged primary shoots can be retained in the event of a late spring frost.

When shoot thinning is performed before inflorescences are visible (shoots 0.8 inch to 4 inches), increased vigor of the remaining shoots and lateral shoot growth may occur as a response, negating the benefits of shade reduction (1). When performed too late (shoot longer than 10 inches), shoots become lignified at the base and difficult to remove.  If performing late thinning, pruning shears should be used if there is risk of damaging the arm of the vine. It also takes longer to thin longer shoots, potentially decreasing the cost-effectiveness of this practice.

Shoot Spacing and Density Recommendations

Generally, shoot thinning on cane-pruned vines is easier, faster, and more straight-forward than spur-pruned vines, which require substantially more decisions regarding what shoots to retain or remove, and where shoots should be spaced along the cordon (2; Figure 2).

Figure 2. Before shoot thinning: spur-pruned (left) vs. cane pruned (right) in Grüner Veltliner, May 26, 2016, Lewisburg, PA.

Plant genotype, soil, and climate are all factors influencing vine vigor potential and capacity to fully ripen a crop.  Therefore, these factors indirectly affect the appropriate number of shoots to retain at thinning.  Many Cooperative Extension websites provide recommendations on range of optimal shoot density based on cultivars grown in their region. [Author’s note: for the eastern US see the additional resources section at the bottom of the post.]

Shoot density targets for Pennsylvania regions:

  • For vinifera cultivars it is recommended to leave 3 to 5 shoots per linear foot of canopy (3, 4; Figure 3). The general rule of thumb is to retain fewer shoots in red varieties and more in white varieties. However, other factors (i.e., cultivar disease susceptibility) must be taken into consideration.

Figure 3. Suzanne Fleishman, graduate student at Penn State in the Centinari lab, is shoot thinning spur-pruned Grüner Veltliner vines (May 26, 2016). Note the differences shoot density between the cordons on the right (thinned) and on the left (unthinned) cordons.

  • For most of the hybrid cultivars it is recommended to leave 4 to 6 shoots per linear foot of canopy (5).
  • For Concord and other native cultivars, as many as 15 shoots per linear foot of canopy can be retained (4).
  • In divided canopies trellis systems, the same shoot density along each cordon should be retained (Figure 4).

In addition to the number, the position of the shoots along the cordon is important.  Ideally, the shoots retained should be equally spaced to promote a uniform, balanced canopy.

Figure 4. Proper shoot density at harvest on Gewurtztraminer vines trained on divided Scott-Henry system in Andreas, PA.

What types of shoots should you remove?

  • Weak, non-fruitful shoots especially if they grow in crowded areas of the canopy.
  • Secondary and tertiary shoots, if a primary healthy shoot has emerged.
  • Shoots arising from the trunk that are not retained for renewal wood (e., new trunks and canes or cordons).

Does shoot thinning improve fruit composition and wine sensory perception?

The associated costs with manual labor and labor shortages are reasonable considerations before implementing vineyard management practices.  This is also true for implementing shoot thinning techniques into a vineyard.  Nonetheless, it is also important to consider the potential benefits from implementing a new practice.

The effects of shoot thinning practices on hybrid varieties are a bit unclear. A previous study on shoot thinning found that shoot thinned Marechal Foch (red interspecific hybrid of Vitis) vines exhibited higher total soluble solids (ᵒBrix) and berry anthocyanin concentrations as compared to un-thinned vines (6). The increase in berry anthocyanin, however, did not translate into higher anthocyanin concentration in the final wine, and furthermore, shoot thinning did not impact the sensory perception of “fruitiness” of the wines (6). In contrast, a study focusing on Corot noir (red interspecific hybrid of Vitis) implementation of shoot thinning provided inconsistent results in grape and wine quality across a two-year (2008-2009) evaluation, which was determined by ᵒBrix, pH, titratable acidity (TA), wine anthocyanin, berry and wine tannin content (7).  Shoot thinning increased berry ᵒBrix, wine alcohol concentration and anthocyanin content only in second year of this study.  While berry TA at harvest was lower (e.g., 2008, un-thinned = 8.6 g/L, shoot thinned = 7.6 g/L), there were no differences in the TA of wine in either year (7).  Shoot thinning also decreased berry seed tannin in 2008 and berry skin and wine tannin in 2009, which could have negative implications for final wine, considering generally low tannin concentrations in hybrid red wines (7).  In an effort to compensate for costs associated with shoot thinning and yield loss, this study on Corot Noir suggested growers increase the price of grapes by 11 to 20% per ton, depending on the average annual market price and yield loss (7).

A study in Fayetteville (Arkansas) on three highly-fruitful French-American hybrid cultivars (Aurore, Chancellor, and Villard noir) found that shoot thinning increased fruit sugar accumulation (ᵒBrix) only in Chancellor and without changes in pH or TA, while a more intense juice color was associated with shoot thinned vines of both red cultivars (Chancellor and Villard noir; 8). In addition, shoot thinning favorably decreased the Ravaz index (yield to pruning weight ratio) for all three cultivars, improving vine balance (8).

The results of these studies suggest that in some situations the costs of shoot thinning may not outweigh the benefits, especially for hybrids that do not command a high market value (Finger Lakes Grape Prices 2016).  However, none of these studies account for potential reduction in disease infections, which may help justify the implementation of shoot thinning in a given vineyard.  For example, it has been found that higher shoot density may contribute to the increased incidence of Botrytis rot infections in susceptible cultivars such as Seyval Blanc (9) and Vignoles (4).

In other cases, shoot thinning improved fruit composition in Pinot Noir and Cabernet Franc for two consecutive vintages (1), and also increased color intensity, phenolic content, and total anthocyanins of Cabernet Franc berries (1). Benefits of shoot thinning on fruit quality and wine sensory perception have been reported for other vinifera cultivars, such us Barbera (10) and Sauvginon blanc (11).

Unless your vineyard is located in a low or moderate vigor site, shoot thinning is strongly recommended for vinifera cultivars growing in the Mid-Atlantic region.

If you want to assess the effects of shoot thinning on fruit composition, plan to leave half of a row of vines un-thinned and thin the remaining half to a consistent number of shoots per foot (e.g., 4 shoots per foot). Alternatively, use two rows (of the same variety and cultivar) to assess the impact of shoot thinning in your vineyard: one row thinned and the adjacent row un-thinned.  These two methods should help evaluate the effect of shoot thinning on berry composition at harvest and if possible, on wine chemistry and sensory perception assuming that the lots of berries can stay separated through wine production.

Effects of shoot thinning on vine physiology

Impacts of shoot thinning on vine physiology and performance are complex.  A study conducted in Italy evaluated the whole-canopy photosynthetic response to shoot thinning using spur-pruned Barbera vines (V. vinifera; 10). Vines were thinned to 5 shoots per foot, reducing the total shoot number by 50% as compared to un-thinned control.  In this study (10) shoot thinning significantly improved grape sugar content, color, and phenolics. Despite the benefits provided by shoot thinning on fruit composition, which has been already reported by other studies, what makes this study unique and interesting it that they investigated the mechanisms behind the improvement in grape quality through the measurement of whole-canopy net carbon assimilation.  Although the shoot-thinned vines had initially lower photosynthesis (carbon assimilation) than un-thinned vines due to the removal of photosynthetic source (leaf), they had regained photosynthetic capacity to levels similar to the un-thinned vines within 17 days of treatment.  This occurred as a result of a substantial increase in both main leaf size and amount of lateral leaves as a result of shoot thinning (10).  Therefore, individual shoots of thinned-vines had a higher supply of assimilates (e.g., sugar) per unit of crop, which can increase sugar accumulation during ripening. This may explain why shoot thinning improved grape composition in Barbera under these growing conditions.

Additional Shoot Thinning Resources

 

References Cited

  1. Reynolds AG., et al. 2005. Timing of shoot thinning in Vitis vinifera:  impacts on yield and fruit composition variables.  56, 343-356.
  2. Intrieri, C and Poni, S. Integrated evolution of trellis training systems and machines to improve grape and vintage quality of mechanized Italian vineyards.  AJEV.  46, 116-127.
  3. Fiola, J. 2017. Canopy Management – Shoot thinning and positioning. “Timely Vit” from UMD Extension.
  4. Walter-Peterson, H. 2013.  Shoot thinning:  Good for the vines, but good for the wines?  Finger Lakes Vineyard Notes.
  5. Martinson, T and Vanden Heuvel, J. Shoot density and canopy management for hybrids. CCE. http://www.fruit.cornell.edu/grape/pdfs/Canopy%20Management%20for%20Hybrids%20-2007.pdf
  6. Sun Q., et al. 2011. Impact of shoot thinning and harvest date on yield components, fruit composition, and wine quality of Marechal Foch.  AJEV. 62:1, 32-41.
  7. Sun Q., et al. 2012. Impact of shoot and cluster thinning on yield, fruit composition, and wine quality of Corot noir.  AJEV. 63:1, 49-56.
  8. Morris, JR. et al. 2004. Flower cluster and shoot thinning for crop control in French-American hybrid grapes.  AJEV. 55:4, 423-426.
  9. Reynolds, AG et al. 1986. Effect of shoot density and crop control on growth, yield, fruit composition, and wine quality of ‘Seyval blanc’.  J. Amer. Soc. Hort. Sci. 111, 55-63.
  10. Bernizzoni, F. et al. 2011. Shoot thinning effects on seasonal whole-canopy photosynthesis and vine performance in Vitis vinifera L. cv. Barbera. Aus. J. Grape Wine Res. 17, 351-357.
  11. Naor et al. 2002. Shoot and cluster thining influence vegetative growth, fruit yield, and wine quality of ‘Sauvignon blanc’ grapevines.  J. Amer. Soc. Hort. Sci. 127(4), 628-634.

 

Maria Smith is a viticulture PhD candidate with Dr. Michela Centinari in the Department of Plant Science.  She specializes in cold stress physiology of wine grapes.  She was the previous recipient of 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.  She is currently funded by the Northeast Sustainable Agriculture Research and Education (NE-SARE) program, a program from the USDA National Institute of Food and Agriculture (NIFA).

Haskap -A New Kind of Wine

By: Jody Timer, Entomology at LERGR & EC

In the colder parts of this state, we are always looking for new berries to make into wine.

Ideally, we are on a search to find berries that will stand cold winters and late frosts.  As an end to this means, three years ago at Lake Erie Regional Grape Research and Extension Center (LERGR & EC) we planted an experimental patch of Haskap bushes (Lonicera caerulea).

Haskap (Blue Honeysuckle) Berries. Photo from: Haskapa.com

Haskap or blue honeysuckle, is an extremely cold hardy, edible berry producing plant, resisting temperatures as low as -46°C (-50.8°F) (Thompson 2008). Even flowers can be exposed to temperatures of -7°C (19.4°F) with no detriment to fruit set. Haskap is also tolerant of a wide range of soil pH (5.5-7.5) (Retamales and Hancock 2012) allowing for production in many different soils. The bushes will survive in the wild in swamp-like conditions, but they thrive in well drained soils. The fruit development period for Haskap starts very early in spring and is very short; 6-8 weeks from bloom to harvest (Thompson 2006). In our climate, Haskap will produce fruit as early as mid-June, coinciding somewhat with the strawberry market. The small blue fruits have a fresh, somewhat tart, raspberry/blueberry to cranberry flavor. They should be purple all the way through before they are fully ripe. These plants do not sucker, need little pruning, and tend to fruit when very young. A Haskap bush can be productive for 30 years. Haskaps are native to Siberia and northeastern Asia (Bors et al. 2012), and were recently introduced to the North American market being advertised for its many claimed health benefits. Some researchers (Bors et al. 2012) believe that haskap could replace blueberries as the new ‘super fruit’. Lonicera have been used widely in folk medicine in northern Russia, China and Japan since ancient times. In recent years, phenolic compounds present in fruit crops, especially berries, have gained much attention due to the accumulating scientific evidence of their potential health benefits. Its juice has 10 to 15 times more concentrated color than cranberry juice. The fruit is high in Vitamin C, Vitamin A, fiber, and potassium.

Antioxidant levels are measured using the ORAC (oxygen radical absorbance capacity) method. A wide variety of food has been tested using this methodology, with the Haskap Berry being rated very highly in comparison with other berries. The berries’ extremely high ORAC value indicates a high anthocyanin, poly phenol, and bioflavonoid content.

In addition to fresh market potential, Haskap can be used in processed products including pastries, jams, juice, ice cream, yogurt, sauces, and candies. These berries also make a nice dark red or burgundy colored wine. The Canadian market is receives about $13.00 per pound, while the Japanese market is about $30.00 per pound of berries (LaHave Forests’ Haskap Day).

Haskap fruits obtain almost full size 4 weeks after blooming and begin to turn purple. The dark skin of the fruit is covered by a waxy coating (bloom) and resembles the outer covering of blueberries and concord grapes. At 5 weeks old they are fully purple but at 6 or 7 weeks old they are fully ripe and tasty. That is for a normal year. But some varieties do develop slower especially if not pruned to let in enough light. Though Haskap is touted as having few disease and insect pest problems, the plant can be negatively impacted by sunburn, mildew and birds.

Haskap Bushes. Photo from aumacksimertals.com

Haskap Bushes. Photo from: honeyberryusa.com

Bob Bors of University of Saskatchewan has been the primary researcher of Haskap varieties. The following is from the research at the University of Saskatchewan (www.usask.ca/agriculture/dom_fruit/index.html):

Like many other fruit crops, haskap requires pollen from an unrelated variety in order to set fruit. Haskap does not have separate male and female plants. When two compatible haskap varieties are planted close to each other, both bushes will set fruit. But it is not enough to have compatible pollen. To pollinate each other both plants must bloom at the same time and be genetically compatible. There is overlap between nearby groups but peak bloom is usually five days different between categories.  Blooming times are dependent on where the Haskap are located. 

‘Tundra’ may be the variety best suited for commercial production at this time (2007).Tundra’s fruits were firm enough to withstand commercial harvesting and sorting at the University of Saskatchewan, yet tender enough to melt in the mouth. Firmness is a rather rare trait especially for large fruited blue honeysuckles. Ranking at almost the top for flavor and fruit size the shape of its fruit was deemed acceptable for the Japanese market. Its fruit is at least 50% larger than blue honeysuckles currently available in Canada and the US. Its firmness and the fact that this variety does not ‘bleed’ from the stem end when picked could make this variety especially suited for Individually Quick Frozen (IQF) processing.

‘Borealis’ has the distinction of having the best testing and largest fruit size in our breeding program as of 2007. (However, there were many good tasting haskap varieties and it was hard to decide) Its fruits were usually twice the size of any of the 35 Russian varieties in our collection of similar age. (Most varieties of haskap/blue honeysuckles seem to have larger fruit as the bushes get older). Unfortunately, this variety does not have the firmness of ‘Tundra’ and it is not suitable for IQF. It tends to get a bit mushy when handled with equipment. It may be best for home gardeners or U-pick operations who can hand pick the delicate fruit. Or if shake harvesting the fruit, the berries will be damaged and will need to be quickly processed. Not only did the breeder and a University panel choose it as having the best flavor, but its top rating for flavor was also verified by a Japanese Company that chose it as the best tasting of 43 samples!” 

The Tundra is by far the hardiest and best growing of the four varieties we have planted at the research station in Erie County (PA).  The Indigo Treat is also doing well. Indigo Gem and Berry Blue have both developed black leaves. We are going to determine this year if the black leaves are from sunburn, mildew, or early dominancy.  Haskap can go dormant as early as mid-August which may be the cause of brown leaves.

Haskapa of Nova Scotia at www.Haskapa.com has a wide variety of products made from Haskaps.  They include syrup, wine, gin, jelly, soap, dried berries, and oils to name a few. This new crop could be grown alongside existing fruit tree orchards, blueberries, raspberries, strawberries, and juice and wine grape vineyards that currently dominate the landscape. If successful, these new crops may serve to supplement the growers’ income, especially in adverse years.

References Cited:

  1. Bors, B., Thomson, J., Sawchuk, E., Reimer, P., Sawatzky, R., and Sander, T. Haskap breeding and production-final report (pp. 1-142). Saskatchewan Agriculture: Regina.
  2. Retamales, J.B., and Hancock, J.F. 2012. Nutrition. In J.B. Retamales and J.F. Hancock (eds.), Blueberries (pp. 103-142). Wallingford: CABI.
  3. Thompson, M.M. 2006. Introducing haskap, Japanese blue honeysuckle. Journal of American Pomological Society 60:4:164-168.
  4. Thompson, M.M. 2008. Caprifoliaceae. In J. Janick and R.E. Pauli (eds.), The Encyclopedia of fruit and nuts (pp. 232-235). Wallingford: CABI.