Category: Archived Articles

By: Judit Monis, Ph.D., Plant Health Consultant

After writing about the presentations at the Unified Symposium last January I promised I would write an article that focuses on the control of the spread of leafroll viruses in the vineyard.  Transmission and spread of leafroll viruses have been documented in all grape growing areas worldwide.  Specifically, leafroll disease has been reported spread in Australia, Argentina, Europe, New Zealand, South Africa, USA, and other important viticulture areas in the world. Different types of mealybugs and soft scale insects can transmit some species of leafroll virus and Vitiviruses. However, long distance dispersion of viruses (as well as other pathogens) is most effective by producing cuttings and grafting.  If you follow my work, you know that I recommend that you plant healthy vines to prevent virus infection in the vineyard.

Grapevine Leafroll Disease

The most important effect of leafroll disease is the production of small grape clusters with uneven ripeness.  The grapes have lower sugar content (reduced brix values). Foliar symptoms include downward rolling, reddening or yellowing of leaves and vary depending on the grapevine variety or winegrowing area. The leaf veins may remain green or take many other colors (yellow, purple, red, etc.).   Sadly, some wine and tourist magazines use photos of infected vineyards to promote their wine regions.  Although all leafroll associated viruses belong to the Closteroviridae (Greek, clostero: thread-like) family, the only species known to be transmitted by insects are found in the Ampelovirus genus (Greek, ampelos: grapevine). Ampeloviruses include the majority of Grapevine leafroll associated viruses (GLRaV-1, -3, and -4). So far, no vector has been reported for GLRaV -2 or GLRaV-7 (but as other viruses are propagated by cuttings). Research has shown that leafroll viruses are able to recombine in mixed infections, generating many variants of similar viruses that scientists define as a quasispecies (i.e., almost a species). These genomic changes have serious implications on virus detection as standard methods may miss infection. Transmission by mealybug and soft scale insects has been reported for GLRaV-1, -3, and -4. Different mealibugs such as the grape (Pseudococcus maritimus), citrus (Planococcus citri), long-tailed (Pseudococcus longispinus), obscure (Pseudococcus viburni) and vine (Planococcus ficus) are able to transmit Ampeloviruses and Vitiviruses non-specifically. Furthermore, work in South Africa has shown that a single individual of vine or long-tailed mealybug is capable of starting a GLRaV-3 infection.

Sampling in The Vineyard:

The correct identification of the disease causal agent is critical for devising a control strategy. Regular visual inspections and sampling of grapevines should be performed to monitor the disease status of a vineyard. It might not always be possible to correlate the presence of virus infection with symptoms, especially with new viral infections. Complicating matters, other viruses, fungi, or nutritional deficiencies can cause similar symptoms in grapevines. Furthermore, vines planted on their own roots do not develop typical symptoms. Symptoms may appear two or more years after top-working a vineyard with a new variety. Viruses associated with leafroll move slowly in the vine and may remain undetected by laboratory testing, unless sampling is done correctly. Collection of representative samples will allow the laboratory to detect the presence of viruses associated with leafroll. The season for testing is important and samples should be collected from vines late in the summer throughout dormancy.

Virus Testing

Two methods can be used for the detection of leafroll-associated viruses: ELISA and RT-PCR.  Each method is designed to detect different portions of the virus. ELISA detects the capsid protein (coat or protective cover), and RT-PCR detects the viral genomic RNA (genetic information).  Therefore, ELISA and RT-PCR complement each other on the detection of virus and virus variants. ELISA stands for enzyme-linked immuno-sorbent assay, and consists of trapping the virus protective protein on a plastic test plate containing specific viral antibodies.  The detection is done through a colorimetric enzymatic reaction (positive samples yield a yellow color). The method is limited to the amount of virus present in the sample (i.e., there is not amplification or danger of laboratory contamination). RT-PCR, is the abbreviation for reverse transcription-polymerase chain reaction.  The method involves the amplification or multiplication of viral RNA present in the vine. The process is specific, and utilizes a couple of primers to start the amplification process.  Primers are essentially artificial copies of a portion of the viral genome. The amplification is repeated many times, each step or cycle continues to makes more copies of the viral segment. Consequently, RT-PCR is a sensitive technique for the detection of plant viruses.

As mentioned above, the sensitivity and specificity of the detection of viruses associated with leafroll is dependent on the method used for diagnostics.  However, detection it is also influenced by the season and part of the vine from which samples were collected as well as the quality of reagents used. While ELISA is known to be less sensitive than RT-PCR, the ELISA has a broader spectrum of detection (i.e., it detects virus variants). On the other hand, RT-PCR (especially Taqman PCR) may be too specific, and could miss the detection of a virus with small changes due to mutation or recombination (e.g., variant species). Lately, fewer quality ELISA reagents are being developed as designing PCR primers is less time consuming. My recommendation is to use ELISA initially (commercial reagents work well for GLRaV-1 to -4) and RT-PCR to confirm infection (or lack of infection).  When mapping infection in a white fruited grape block such as Chardonnay or Sauvignon Blanc, ELISA may be the only economical way of determining the leafroll disease status of specific vines as many samples must be tested in a yearly basis.

Leafroll Disease Management and Control Strategies

To manage leafroll disease, it is important to develop a map of virus infected vines. The map will provide information of virus spread and determine the pattern of infection.  A random distribution of symptomatic vines would generally be associated with planting infected vines. While symptomatic vines aggregated or clustered in one area of the vineyard block is an indication of virus spread.  The initial assessment must be done using a testing lab to determine the presence of a virus species capable of being transmitted.  Once the vineyard manager is familiar with symptoms, the mapping could be done by visual observation.  It is much easier to determine the characteristic leaf roll disease symptoms in red fruited varieties.  In white varieties it may be possible to train eyes to determine the presence of infection but likely will rely on the confirmation of the presence of virus by testing vines.

Effective disease control requires the availability of clean planting stock (i.e., certified disease-free tested). However, to ensure that the vineyard remains disease free, the grower must be aware of the presence of virus infection in neighboring vineyards. It is important to devise procedures to protect a healthy vineyard from potential disease introduction. The presence of insect vectors and ants should be routinely monitored and controlled. Unfortunately, mealybugs are not always easy to observe in the vineyard, however the presence of ants are usually associated with the presence of mealybugs. Special traps (including pheromone traps) are available to monitor the presence of mealybug infestation. The dispersal of mealybugs by birds, wind, field equipment, and/or workers are responsible for long distance spread of virus. Sanitary practices such as fallow periods, sanitation of equipment, and sanitation of field worker’s clothing are recommended to avoid moving disease vectors from one vineyard block to another.  I always recommend to start work in the non-infected blocks and move workers to infected blocks at the later part of the day.

Controlling the spread of viruses requires strict protocols for handling vines and performing cultural practices in the vineyard and nursery. Hot water treatment of vine cuttings and grafted vines are effective controlling the movement of mealybugs from one site to another. Other recommended practices include establishing wind traps, planting insecticidal cover or border crops, using site dedicated clothing and/or shoes for workers, and avoiding the use of potentially contaminated equipment in the vineyard.

Ultimately, the removal of infected vines or entire blocks will be key to reducing the source of infection.  Guidelines call for rouging (removal of individual infected vines) if there is less than 25% disease incidence and entire blocks (greater than 25% disease incidence). A common mistake is the removal of a portion of the infected vineyard block (see photo 2).  This decision is made to avoid production losses at the vineyard. However, in no time, the newly planted vines will become infected by the same virus present in the other portion of the vineyard.

The control of leafroll spread needs to be based on a concerted effort among growers. In California the development of a network of neighboring growers has allowed open discussion of infection status of blocks and applied control measures. The use of cultural practices (especially sanitation and insect control applications) should be coordinated and scheduled to include area-wide treatments as grapevine viruses and their vectors do not know or respect neighboring borders.

  Judit Monis, Ph.D. provides specialized services to help growers, vineyard managers, and nursery personnel avoid the propagation and transmission of disease caused by bacteria, fungi, and viruses in their vineyard blocks.   Judit (based in California) is fluent in Spanish and is available to consult in all wine grape growing regions of the word.  Please visit juditmonis.com for information or contact juditmonis@yahoo.com to request a consulting session at your vineyard.

By: Dr. Richard E Smart and Amaya Atucha

We wrote this article to promote the use of the Scott Henry training system in vineyard regions of North America; for reasons which we do not completely understand the system has been overlooked,  under-researched and also under-promoted. For those growers who use this system, mostly overseas, the benefits are substantial. They might be summarised as improved yield and fruit composition and reduced disease incidence. Wine quality is also improved. The system is not difficult to manage, contrary to some rumours in this regard. It is a matter of learning new tricks, mostly about timing, so not too difficult for commercial grape growers.

For those growers prepared to try new ideas, you will be rewarded, and the winemakers (and bank managers) will smile.

Why the Scott Henry?

Canopy Management 101

The basic aim of canopy management is to train grapevines in in such a way that yields are promoted, as is desirable fruit composition and disease avoidance. It follows a few basic principles, which follow:

• Maximise sunlight interception, remember it is Sunlight into Wine. Preferably use north-south rows, spaced about as far apart as they are tall. If you are in a hot, sunny region, you might avoid N-S rows and the heat caused by afternoon sun on west-facing canopies. Taller canopies are of course more efficient than shorter ones.
• Maintain a sufficiently wide spacing between shoots to avoid dense canopies, around 5 shoots per foot of canopy length, or 2.5, 2-bud spurs per foot of canopy. Most canopies are more crowded than this. Shading of bunches has serious effects on wine quality, and shading of the base of shoots reduces bud fruitfulness.
• Fruit exposure will generally be sufficient in such low density canopies as above; perhaps if very leafy there may be a need for some leaf or lateral removal.
• Vine balance is very important, and this is largely determined by winter pruning level; the bud count should be matched to the vineyard vigor. The best way to assess this is by weighing prunings on a few average vines. To obtain vines of moderate vigour, the rule of thumb is retain about 14 buds per pound pruning weight. This is often more buds than are normally left. Ideally the vines should be spaced 5-6 ft apart in the row.

These general rules apply to any vineyard trained to any system, not just the Scott Henry. The Scott Henry (SH) is like the Smart Dyson (SD) and Geneva Double Curtain (GDC) systems. All three have two feet of canopy per ft of row, in other words they are a “divided canopy” system. The Scott Henry and Smart Dyson are called vertically divided. One canopy grows upwards, one downwards from mid height  (3 ½ ft) fruiting zones. The GDC on the other hand is horizontally divided, with two pendant curtains about 3 ft apart.

Managing the Scott Henry

The Scott Henry is a cane pruned system, using two or four canes. The Smart Dyson is spur pruned, with spurs pointing upwards and downwards from a mid-height cordon. We will discuss the management of the Scott Henry only here.

Normally, for vigorous vines we prune to four canes, two on a lower fruiting wire at around 40”, two on an upper fruiting wire at about 46”, on the opposite side of the post and on the upwind side. An extra wire is used for the SH, a moveable foliage wire to help downwards shoot positioning.  At winter pruning, this rests about opposite the top fruiting wire, and at early flowering it is placed on top of the shoots from the bottom canes after they are separated from those growing upwards; subsequently, after fruit set it is moved downwards and attached, so positioning the shoots downwards. When pruning remember not to wrap the bottom canes too tightly, one or two wraps is best, and secure the ends of the canes.

At the beginning of flowering, and before the tendrils start to attach, slide your arm into the canopy to separate shoots from the top and bottom canes.  Place the extra moveable foliage wire on top of the shoots from the bottom cane, and they will lean out into the row, assisted by any wind. Shoots from the top cane will form the top canopy, and they are trained vertically upwards between foliage wires, as is normal for VSP.

Then, at around early fruit set, move the bottom moveable foliage wire downwards and attach it to the post, say 2 ½ ft below the fruiting wire. This will form the second, downward pointing canopy.  Remember that you will need to apply any herbicide before flowering.

Normally shoot positioning the Vertical Shoot Positioned canopy (VSP) takes 3-4 labor passes through the vineyard with well managed teams, and requires 12 to 16 hrs per acre. This figure might be increased by say 25%  maximum when using Scott Henry.

Responses to Scott Henry

Training with Vinifera

The conversion cost is not high, to add only one wire per row to train shoots downwards, and a very modest increase in labor input, for shoot positioning. The benefits are however substantial, with yield increase to 30% or more, no change in other costs (apart from harvest), and typically less disease. It is well known that powdery mildew and Botrytis are higher in shaded canopies, and less for Scott Henry than VSP. Because of improved bunch exposure, there is better color, flavour and phenolics in vines trained to Scott Henry.

Most experience around the world is with vinifera grapes; in fact Oyster Bay wines of New Zealand has 5,240 acres of Scott Henry planted in both NZ and Australia, no doubt the largest in the world. Results from their vineyards reinforce the message above, and on a grand scale!

Responses to Scott Henry Training

With Hybrid Grapes in Wisconsin

Cold climate hybrid grapes cultivars have propelled the expansion of the grape and wine industries in the Northeast and upper Midwest of the United States, mostly due to their superior midwinter hardiness compared to vinifera and other hybrid cultivars. However, cold climate hybrids possess high vegetative vigor which can be intensified when vines are grown in very fertile soils, and summer rainfall such as in the Midwest. The high vegetative vigor of these hybrids can be challenging for growers to manage, and often results in dense canopies with shaded fruit that is high in acidity and has poor color development, as well as an overall delay in ripening. To control vigor, growers will usually hedge and skirt shoots multiple times during the season, and will implement shoot and leaf removal to increase light exposure of clusters, all of which requires labor and increases production costs. Particulary time consuming is the task of tucking shoots into the trellis wire in the VSP system, which can be a constant battle with cultivars that have a procumbent (droopy) growth habit such as ‘Brianna’ and ‘La Crescent’.

Alternatively, divided canopy training systems, such as Scott-Henry (SH), can be used to control vine vigor, as these systems increase the number of shoots and clusters per unit of row length, compared to those grown on single canopy systems like VSP or high wire. Studies across in the Midwest of the United State (Atucha and Wimmer, 2016; Cochran and Nonnecke, 2016) have shown that cold climate hybrids trained on divided canopy systems can achieve higher yields, reduce canopy shading, and improve fruit composition, compared to single canopy systems.

In a 5-year training system evaluation study in southern Wisconsin, yield of vines trained to the SH system produced more than double the yield than those trained to the vertical shoot positioning (VSP) system, and 25-35% more than vines trained to the high cordon (HC) system. For example, in ‘Frontenac’ the 5-year average yield on SH was 30 lb/vine (  8.7 t/ac), compared to 16 lb/vine (4.7 t/ac) in VSP, while in ‘Marquette’, HS and VSP produced 17 and 10 lb/vine (5 and 2.9 t/ac), respectively. In addition to higher yields, vines trained in the SH system had more consistent yields year to year, compared to the high variability in yields observed in VSP.

The higher yields in SH resulted in a considerable reduction in vegetative vigor, which required no to minimal hedging to control shoot growth in vigorous cultivars such as ‘Marquette’ and ‘La Crescent’, and an overall more open canopy with a higher percentage of clusters exposed to sunlight (Wimmer et al., 2018) .  There were no differences in sugar and acid composition at harvest between the higher yielding SH vines and those in VSP or HC, despite the significantly higher crop load of vines trained to SH. Separate studies in Wisconsin have shown that sunlight exposure improves berry colour and phenolics. A recent article in this magazine (Smart 2018) emphasised the need to do shoot positioning on the high wire trellis to avoid shading, which causes loss of yield and quality.

Conclusion

We think that Scott Henry and Smart Dyson might have application in the Midwest USA, as has been found elsewhere. Certainly the initial research results are encouraging. The SH training system is a great option to control vegetative vigor and increase yields in cold climate hybrid grape cultivars without reducing fruit ripeness, and quality for winemaking will likely be improved.

References Cited

Atucha, A. and M. Wimmer. 2016. Brianna, Frontenac, La Crescent, and Marquette Training Trial. West Madison Agricultural Research Station (WMARS), Verona, WI. Northern Grapes Project publication. http://northerngrapesproject.org/wp-content/uploads/2016/02/WI-training-study-Year-4.pdf

Cochran, D.R. and G.R. Nonnecke. 2016. Iowa Training Systems Trial. Snus Hill Winery, Madrid, IA. Northern Grapes Project publication. http://northerngrapesproject.org/wp content/uploads/2016/02/IA-training-study-Year-4.pdf.

Smart, R. E. (2018) Managing high wire trellis for improved yield and quality. The Grapevine. Nov-Dec, pp 54-58.Wimmer, M., Workmaster, B. and Atucha, A. 2018. Training Systems for Cold Climate Interspecific Hybrid Grape Cultivars in Northern Climate Regions. HortTechnology 28(2): 202-211.

About The Authors

  Dr. Richard Smart: is an Australian viticulturist and leading global consultant on viticulture methods and is often referred to as “the flying vine-doctor”. He is considered responsible for revolutionizing grape growing due to his work on canopy management techniques.

  Dr. Smart is a graduate from Sydney University with Honors in Agricultural Science in 1966. Additionally he holds the degrees M.Sc (Hons) from Macquarie University following a study of sunlight use by vineyards, a Ph.D from Cornell University in New York State studying under the Professor Nelson Shaulis, and in 1995 awarded a D.Sc. in Agriculture by the Stellenbosch University, South Africa, in recognition of research into canopy management effects on vineyard yield and quality.

  Dr. Smart is the author of the book Sunlight into Wine as well as a contributor to several trade publications, and the viticulture editor of The Oxford Companion to Wine. Consulting has been a full time occupation since 1991, and he has consulted to over 300 clients worldwide. While many clients want to use Richard’s expertise in canopy management to improve wine quality and vineyard yield, complete viticultural advice has been given on a range of issues like choice of site, variety, rootstock, irrigation and nutrition management.  Dr.Richard E. Smart: International Viticultural Consultant, Smart Viticulture, Truro, UK, richard@smartvit.com.au

Amaya Atucha: is an assistant professor and Gottschalk Chair for cranberry research in the department of Horticulture at the University of Wisconsin-Madison and State Fruit Crop Specialist with UW Extension. She earned a B.S. in horticulture from the Pontificia Universidad Católica de Valparaíso (Chile) and a Ph.D. in horticulture from Cornell University. Her research program focuses on fruit crop physiology and production of deciduous fruit crops, predominantly cranberries and cold climate grapes, and her extension program delivers up to date, research-based information to fruit growers in Wisconsin. She edits the Wisconsin Fruit Newsletter, a biweekly newsletter distributed statewide in Wisconsin, and is a contributor to the Cranberry Crop Management Journal, a publication highlighting research and extension in cranberry production at UW-Madison.

By: Judit Monis, Ph.D.

This year I was invited to speak at different events organized by the Chilean Nursery Association (AGV) and Wines of Chile. While in Chile, I attended the 19th Congress of the International Council for the study of virus and virus-like diseases of the grapevine (ICVG). The ICVG meeting was held and hosted in Viña Santa Carolina Winery facilities near Santiago.  While I was traveling in South America, I had an opportunity to visit vineyards in Argentina and Chile.  Today I will share information I learned about winegrowing in Argentina and Chile.  As you know my interests are in grapevine diseases, how to prevent disease development and spread in the vineyard.   So, it will not be surprising that this article will focus on vine diseases.

Grapevine Diseases Originate Where Vitis Species Originate

It is easy to guess that grapevine pathogens (disease causing agents) originated at the same place where Vitis (the grapevine genus) species originated.  These disease agents (bacteria, fungi, and viruses) were introduced to other places in the world with the propagation and planting material.  Specifically, the varieties and clones that are grown in vineyards belong to the Vitis vinifera species (of Eastern European and Asian origin) while the rootstocks grown commercially belong to American Vitis species.  When grape cultivation started countries were not set up with quarantine programs, neither modern diagnostic tools we use today (PCR, ELISA, etc.) to detect pathogens were available.  Consequently, since the early days of grapevine cultivation European and American grapevine pathogens have been moving from one site to another for many generations.

Argentine and Chilean Grape growing Regions are Strikingly Different

  Being from Argentina, I frequently visit vineyards and wineries in South America.  Argentina ‘s viticulture is very different from what I am used to in California growing regions.  Most of the vineyards in Argentina have planted vines on their own roots (i.e., not grafted onto a rootstock) as the philoxera pest is not commonly found in Argentine grape growing areas.     Besides providing protection from philoxera, rootstocks confer resistance to nematodes, salinity, and can control the vigor of the vines in the vineyard.   Consequently, more vineyards in Argentina are being planted with grafted vines, especially in Mendoza’s newer and more sophisticated growing regions (Valle de Uco).   In contrast, the vineyards in Chile are very similar to the ones I visit in California and strikingly different from those in Argentina.   The majority of the vines in vineyards are grafted and trained in a similar fashion to Californian vineyards. The Andes Mountains that divides Argentina from Chile influences the climatic conditions of each of the countries.  Therefore, the rainy seasons, availability of water and stresses present in each winegrowing area are very different.

Grapevine Diseases are Found Wherever Grapevines are Grown

When it comes to diseases Argentine and Chilean viticulture is not different from other growing areas.   As I mentioned earlier, common diseases caused by Leafroll viruses, Vitiviruses, Fanleaf, Agrobacterium, and fungal trunk diseases must have arrived on site when plant material was imported.  These are important diseases that affect both grape quality, yield, and longevity of the vineyards.  In Chile and Argentina, I have witnessed the presence of Syrah Decline, a disorder that affects both grafted and not grafted plants.  At the ICVG meeting, Joshua Pucket from UC Davis Foundation Plant Services reported that Syrah Decline symptoms are linked to genetic markers present in certain Syrah and Shiraz clones.   Interestingly, when symptomatic Syrah selections were subjected to the meristem tissue culture technique used to eliminate known viruses and viroids, the symptoms persisted, suggesting that Syrah Decline is not caused by any of these infecting agents.  Research in France support these findings as symptoms are restricted to certain grapevine genotypes.  The news that Syrah Decline is a genetic rather than pathologic disorder will help growers prevent planting certain genotypes to avoid loss of production.   It is expected that we will learn more about this disorder as more research is published on this topic.  To date, surveys in both Argentine and Chilean vineyards were not able to detect Grapevine red blotch virus (GRBV).  The most likely reason for the lack of GRBV in Argentina and Chile is that these countries have historically imported grapevines from Europe and the virus so far has not been reported in EU vineyards.

None of these South American Countries have a Grapevine Clean Planting Certification Program

Grape growers and winemakers are aware of the detrimental effect of grapevine pathogens and would prefer to purchase and plant certified grapevines. Unfortunately, neither Argentina or Chile have a current certification program.  In other words, certified pathogen free vines (scion or rootstock varieties) are not available.  This is not completely true, as I learned that Argentina has one certified Malbec clone available. However, there is no use of having a certified scion if it is to be grafted onto a non-certified rootstock.  Consequently, most nurseries and growers are grafting non-certified scion and rootstock varieties.  In Argentine the grapevine certification program is going through administrative revision.  The current law requires that all mother plants are tested every year using the woody indexing method.  However, this is not practical as the results of this test are obtained two years after starting the index. The proposed changes include the application of molecular (PCR, ELISA) instead of biological testing (index) to detect viruses in the foundation and nursery increase blocks.  In Chile, supported by public funding a virus tested germplasm collection is being preserved.  It is expected that the material will become available to interested nurseries that could multiply and distribute the material for planting new healthy vineyards.

In both countries, the available planting material produced at the nurseries is not sufficient to fulfill the demand of the industry.  Therefore, grafted vines can also be imported from “approved” nurseries primarily from Europe (France and Italy) and must pass the government quarantine and sanitation requirements.  Generally, quarantine is done at facilities owned by the importing party as neither SENASA or SAG, the National sanitary authorities in each of the countries have the space to complete the quarantine in their facilities.

It is my hope that, with time, future changes will include the availability of certified pathogen free tested and true-to-type scion and rootstock planting material.  Only with clean planting grapevine material these important wine grape growing areas will see an improvement of the health and longevity of their vineyards.

  Judit Monis, Ph.D. provides specialized services to help growers, vineyard managers, and nursery personnel avoid the propagation and transmission of disease caused by bacteria, fungi, and viruses in their vineyard blocks.   Judit (based in California) is fluent in Spanish and is available to consult in all wine grape growing regions of the word.  Please visit juditmonis.com for information or contact juditmonis@yahoo.com to request a consulting session at your vineyard.

By: Tracey L. Kelley

Irrigation system maintenance is a vast topic of discussion—so much so, to do this article, we needed a team of experts to address it—in two parts. Mark Hewitt, the district sales manager for the ag products division of Rain Bird Corporation in Azusa, California, put it this way: “These are huge topics! People write books about these subjects! 1,500 words? Good luck!”  Yet we understand it’s essential to initiate an open forum periodically to ask about research, various applications or innovations that might help keep your system—and the entire growing season—flowing smoothly.

In the first part of this story, the experts provide tips for what you may need to know immediately to start operations and remedy any issues. In the July-August issue of The Grapevine Magazine, we’ll feature further concepts and suggestions from our experts.

In addition to Hewitt, other people extending their knowledge include:

• Guy Fipps, Ph.D., P.E., professor and extension specialist of irrigation and water management at Texas A&M University, College Station, Texas; in collaboration with Charles Swanson, extension program specialist, Texas A&M University
• Jacob Hernandez, CCA, owner, JH Ag Consulting, Santa Margarita, California; in collaboration with James Anshutz, AGH20, irrigation engineer with Netafim USA in Fresno, California; and the Cal Poly SLO Irrigation Training and Resource Center, San Luis Obispo, California
• Steve Purvins, owner, The Vineyard at Lawton Hall in Bushwood, Maryland, which produces Vidal Blanc and Chambourcin grapes

Let’s Get It Up and Running

Regionality, post-harvest vine vigor, and winter precipitation are all factors determining whether a vineyard irrigation system gets shut down off-season. Some growers close it all off, while others use irrigation intermittently, but still need to check various components. A few growers know by late March if their vines have delayed spring growth due to insufficient water during colder months, and can only plan for next year to enable better health with a post-harvest irrigation plan.  For the majority of producers, it’s time for a spring tune-up. De-winterizing a system follows numerous steps.

  Fipps started the process with the basics:

1. If the irrigation system was idle all winter, the system should be inspected for any damage that could have occurred. Turn each station on for a cycle and visually inspect each for visible tears or leak in the tubing, as well as dry areas from clogged drip emitters.
2. While running, also check the pressures and flow rates—if pressure gauges and flow meters are installed—to ensure they correspond to system requirements.
3. It’s also recommended to flush each drip line for a short period to remove any sediment or biologicals like algae that could have accumulated. Flushing the lines can help reduce problems during the irrigation season.

Fipps added, “All drip filters should be removed and properly cleaned before start-up. If any filter is damaged or unable to be cleaned, it should be replaced. Additionally, for automatically controlled systems, make sure all valves are opening and closing correctly. Valve solenoids and diaphragms can become damaged over time, requiring maintenance or repair.”

Hernandez provided a detailed four-part checklist:

1. Pump station hardware: start system and make a note of any leaks from broken pipes, couplers and other fittings. Repair and replace as necessary. Exercise manual and automated valves. Clean air vents and replace any damaged units. Check for proper pressure settings of any pressure reducing or sustaining valves.
2. Filtration systems: Remove screens and pressure wash to remove debris. Treat with a chemical solution to kill biological slimes, then clean and replace. Check sand media and refill and replace as needed. Sand media should have sharp edges—if rounded, replace. Check settings and function of automated backflush system, and make sure differential across filters is less than 10 psi. A properly-functioning filter station is one of the most critical components in maintaining uniformity of drip and micro-irrigation systems.
3. Check your pump flow rates and pressure monitoring systems for each irrigation block or set. If you’re using a variable frequency drive (VFD), schedule an appointment to have the VFD serviced. Check settings and make adjustments as needed based on current conditions that may differ from when the VFD and pump station were installed. Check flow meters and pressure gauges for accuracy and calibrate or replace any damaged or unreadable gauges.
4. While the pump is running, check the irrigation set perimeter to make sure all line ends are receiving water and re-attach any disconnected lines. Drive every line to check riser tee screens for debris and clean or remove and replace with plain washers. Check flow rates of emission devices and replace plugged or partially plugged devices as necessary. Check riser tees, couplers and hose ends for leaks, and replace or repair as needed.

“Review the previous season with your irrigation supervisors to understand the most common problems the irrigation team is dealing with,” Hernandez told The Grapevine Magazine. “Plan to fix the biggest issues in a systematic fashion. Often, a simple fix will open up a lot of time for your irrigators and enable them to spend more time on preventative maintenance instead of temporary fixes.”

  Hewitt also offered a multi-check process:

1. For surface-mounted pump stations, check for leaks, broken or cracked pipes and damaged pressure gauges. Leaking packing glands or bearings need to be adjusted—usually tightened or replaced.
2. Examine filter stations. Screens and disc filters need to be pulled and inspected for damage and wear. Media filter covers need to be pulled, and their sand checked for cleanliness and quantity. Add new sand if levels are low and also check backflow restrictor valves if sand levels are low. Clean control water filers, too.
3. Water meters, if present, need to be pulled. Paddle or impeller types should be checked for freedom of movement and re-calibrated if needed.
4. Clean site tubes, inspect gauges for freeze damage and accuracy and actuate backflush valves one at a time to ensure they open and close completely.
5. All electric solenoids need to be checked to ensure they’re in good working order—no swelling of coils, plungers move freely, and plungers pull in when energized and deactivated by the controller.

When asked what issues managers sometimes encounter that Rain Bird representatives help them solve, Hewitt said, “We’re asked to troubleshoot everything from the water source to the figure eights at the end of the drip line laterals. [We help with] pumps, filters, controllers, valves, hoses and emitters. Filters are one of the most common problematic components of a low-volume system, especially if it’s over three years old,” he said. “Another common issue is plugged or low-flowing emission devices. Remember, no dripper will ever be as clean as it was when it came out of the factory!”

Purvins uses above-ground drip irrigation tubing suspended 8 inches high on a trellis wire and run down each vineyard row, spaced 8 feet apart. He has 0.5 gallons/hour emitters every 96 inches, and his system is supplied by a drilled well. Since he doesn’t irrigate during the winter, his startup is simple: “I have underground drain valves that I use to empty the lines before winter. I just check that all valves are closed in the spring before using the system.”

Handling System Damage Due to Excess Water

Northern California’s heavy rainfall in January and February caused some of the most problematic floodings in 20 years. Areas of the Midwest hit by “bomb cyclones” and significant snowfall melt triggered what scientists at the National Weather Service classified as “major to historic and catastrophic” floods. Some parts of the East Coast are still dealing with the effects of extensive rains and flooding from 2018. We asked our experts: how do these weather events affect vineyards and their irrigation systems?

“In Texas, where most vineyards use drip irrigation, flooding likely will do extensive damage to the drip irrigation system and possibly to pumps as well,” said Fipps.

Hewitt agreed. “This will be a new problem for growers with low-volume drip systems. Areas that were under floodwater this winter that have drip tubing with emitters will need to be very diligent during flushing after the flood waters recede—and some of these drip lines may not recover,” he told The Grapevine Magazine. “Excess water and debris could have entered into the exit bath areas of the driplines. If this material is allowed to dry and harden, most likely no amount of line pressure is going to clean this debris out of the emitter exit pathway.”

Hernandez added, “Flooding could damage infrastructure like pumping stations, pipes and laterals (drip hoses). Carefully inspect any affected equipment. Consider strategies for diverting water to prevent damage from future flooding episodes,” he said. “Additionally, my number one concern would be the impact of flooding events on my soil health. How much topsoil did I lose? What was deposited onto my field? Take soil samples at multiple depths throughout the field and start making necessary amendments as soon as possible.”

In part two of our irrigation system maintenance and upkeep article (Grapevine Magazine, July/Aug 2019), these experts share their views regarding ongoing system checks, typical problems often overlooked, monitoring water quality and critter control.

(Sources)

All listed above, plus:
Western Farm Press
https://www.farmprogress.com/grapes/post-harvest-irrigation-can-help-prevent-uneven-vine-growth-next-spring

Wine Enthusiast

Discover
http://blogs.discovermagazine.com/imageo/2019/03/19/satellite-imagery-reveals-historic-midwest-flooding/#.XK4V1th7mCg

By: Nan McCreary

We hear a lot about hybrid cars, hybrid fruits, hybrid vegetables and even hybrid animals, but what about hybrid grapes? Traditionally, wines made from hybrid grapes have been a non-starter for wine lovers, but that’s about to change. As we prepare to enter a new decade, more and more wine professionals are taking a second look at hybrids, and pioneering winemakers and scientists are working to improve existing varieties and introduce new ones.

A Double-edged Vine

Hybrid grapes are the product of crossing breeding two or more Vitis species. In the U.S., these grapes are cultivated by combining the rootstock from Vitis vinifera, a European wine grape species, and North American vines, commonly Vitis labrusca and Vitis riparia. Vitis vinifera is the source of noble wines so popular today, including Merlot, Cabernet Sauvignon, Pinot Noir, Sauvignon Blanc, Riesling and Chardonnay. Vitis labrusca is widely distributed across central and eastern Canada, and the central and northeastern part of the U.S. Vitis riparia originates in central and eastern Canada and the United States, extending as far west as Montana. Grapes from Vitis labrusca and Vitis riparia in their original form are rarely used for winemaking.

French-American hybrid wines were created as a solution for Phylloxera which devastated the vineyards of Europe in the mid-1800s. Because American grapevines were resistant to phylloxera—as well as powdery mildew, rot and other disease— scientists responded to the crisis by grafting Vitis vinifera vines onto to disease-resistant American rootstock. While these new varieties did provide a solution to phylloxera, the grapes crossed with Vitis labrusca and Vitis riparia were not as popular as those crossed with Vitis vinifera. Critics panned the hybrids because they lacked “purebred” status as well as the depth and complexity of Vitis vinifera grapes. Also, hybrid wines were often panned as “foxy,” a term describing juice that smells or tastes like musky Welch’s grape juice. These undesirable attributes caused many European countries to prohibited the use of hybrid grapes in quality wines.

Turning Tides

Today, the tide is turning for these much-maligned varieties. Unlike sensitive vinifera grapes that require particular weather conditions and soil to thrive, French-American hybrids made from Vitis labrusca and Vitis riparia can grow just about anywhere. They withstand harsh winters—some surviving in temperatures as low as -30 F—as well as arid, brutally hot Arizona summers. Hybrid cultivars are critical to the rapid changes in eastern and central vineyards. With growth in wine-related tourism exploding, wineries are showing up in locations where wine production was once thought impossible. Hybrids are also increasingly popular because they are resistant to many diseases, which encourages growers to farm organically. Even the EU is encouraging producers to reconsider hybrid grapes, as cost and health concerns from fungicides continue to rise.

Much of the success of hybrid grapes today can be attributed to the enology departments at the University of Minnesota and Cornell University, which have been breeding hybrid wine varieties since the 1970s and 1980s. Minnesota’s wine grape research enjoys recognition as one of the top programs in the U.S., with the goal of developing high-quality, cold-hardy and disease-resistant wine grape cultivars. Cornell is home to one of the top viticulture and enology programs in the world with international recognition for its expertise in breeding table, juice and wine grapes adapted to cool-climate growing regions. Programs at both schools dedicate research to producing new grapes with potential for flavor and winemaking, with an ideal balance between cold-hardiness and delicate flavors.

The following is a list of the most popular French-American hybrids in the U.S., according to “The Grape Grower’s Handbook” by Ted Goldammer and used with permission from the publisher, Apex Publishing.

Red Wine Varieties

Baco Noir:  Produces wines that have been variously described as “Rhone-style” or “Beaujolais-style.” It is characterized by high titratable acidity at fruit maturity and produces wines of good quality that are normally deeply pigmented but low in tannin content. It develops a fruity aroma associated with aspects of herbs. The wine is grown primarily in Canada, New York, Oregon and Nova Scotia.

Chambourcin:  Considered one of the best of French-American hybrids, is a highly rated wine used often used for blending with other wines. The grape produces a deep-colored wine with a full, aromatic flavor, and no unpleasant hybrid flavors. It can be made into a dry style or one with a moderate residual sugar level, giving it a pleasant but not overbearing sweetness. Wines from this grape are higher in tannins than other French-American hybrids. Varietal descriptors include raspberry, cloves, cherry, plum, and tobacco. The wine may be found in Ontario (Canada), Missouri, Pennsylvania, Michigan, North Carolina, Illinois, Indiana, Ohio, Kentucky, New York and New Jersey.

Chancellor:  The wine quality is among the better of the French-American hybrids, and it does well alone or in blends. It produces a medium-bodied red wine which is capable of aging well. It tends to be very colored, and care should be taken not to extract too much color from the skins. It’s an important grape in the cooler regions of Canada and the U.S., such as the Finger Lakes Region of New York.

Frontenac:  Produces deep-colored wines with cherry, blackberry, black currant, and plum notes. It can also be used in production of port-style-wines. The University of Minnesota developed the grape and released in 1996. Because Frontenac can survive in temperatures as low as -30 F, it is planted across the Northeastern part of the U.S. and Canada and is one of the most commonly planted wine grapes in Minnesota.

Maréchal Foch:  Possesses Burgundian characteristics, having a vibrant, deep purple color, with a light-medium structure and dark berry fruit characteristics. Some tasters find the similarities to Burgundy Pinot Noir become more pronounced with age. Maréchal Foch is one of the hardiest of the hybrids and is widely grown commercially throughout the Midwestern U.S. and Canada.

Norton (Cynthiana):  Produces a rich, full-bodied dry red wine with berry flavors and spicy overtones. It can be used in varietal wines, including ports, but may also be blended with other reds. These wines have an intense color. Norton is grown in the Midwestern U.S., Mid-Atlantic States, Northeastern Georgia and, most recently, in California.

White Wine Varieties

Cayuga:  Produces a European style white table wine, which has medium body and good balance. This versatile grape can be made into a semisweet wine, which brings out the fruit aromas, or if oak aging, into a dry, less fruity wine. The Cayuga White grape was developed especially for the Finger Lakes Region in New York by Cornell University, and is known for producing fine sparkling wines.

Chardonel:  Is a cross of Seyval Blanc and Chardonnay that produces an excellent wine, with aromas characteristic of both parents. Chardonel has the potential for fine-quality, dry still wines produced with barrel fermentation and/or barrel aging. Chardonel is popular in the Midwestern U.S. and the Mid-Atlantic states.

Seyval Blanc:  Produces a fresh, crisp wine that is often described as good with attractive aroma, but the body is somewhat thin. Malolactic fermentation or barrel fermentation followed by oak aging will enhance the quality. The variety is also popular in Canada and the Midwestern U.S. and the Eastern U.S., particularly New York.

Traminette:  Is a late mid-season white wine grape which produces wine with distinctive floral aroma and spicy flavors, characteristic of its Gewürztraminer parent. Traminette’s relatively high acid and low pH help complement its fresh-fruit aromas and flavors. The wine can be made dry or sweet but is usually finished with some residual sweetness. The wine is grown on the East Coast of the U.S. and in the Midwest.

Vidal blanc:  Is considered one of the best of the white French-American hybrids. The wine produced from Vidal blanc is fruity, with grapefruit and pineapple notes. The wines produced can be quite versatile, ranging from off-dry German style wines to dry, barrel-fermented table wines. Due to its high acidity and fruitiness, it is particularly suited to sweeter, dessert wines. It is especially popular as an ice wine in Canada. You can also find Vidal Blanc the Eastern and Midwestern U.S.

Vignoles:  Produces excellent wines of many different styles, depending on the region where the grapes are grown. Most commonly, however, Vignoles is produced as an off-dry wine or as a dessert wine, especially when picked late in the season. The fruit can have a high sugar content while retaining high acidity. Vignoles is one of the mainstays of the Eastern North American wine industry. It is also prevalent in the Midwest and been called “Missouri’s favorite white wine.”

This list is by no means comprehensive. Cornell and Minnesota have created hundreds if not thousands of new varieties. In 2006, Minnesota introduced two cold-hardy grapes, Marquette and La Crescent. Marquette, a red grape, is said to have the characteristics of Vitis vinifera grapes, while La Crescent has been touted as the perfect choice for Riesling lovers. More recently, Minnesota released the Itasca hybrid, which has drawn comparisons to Sauvignon Blanc.

While French-American hybrids may not have reached the international status of Vitis vinifera wines, the future is wide open for these varietals. Researchers are continuing to develop grapes that produce desirable qualities, and growers are experimenting in site selection, growing techniques and winemaking. Hybrids are getting a second look, too, as an option to offset climate change. Researchers at the University of California Davis are trying to create heat resistant grapes that produce quality wines. In France, the INAO has approved a third category of grape varieties “for climate and environmental adaption” that allow regions to conduct their research on heat-resistant grape varietals.

Wines made from hybrid grapes continue to improve by leaps and bounds. Whether used to offset global warming, promote sustainability, due to changes in consumer tastes or the “localvore” movement, the time is right for these former “mutts” of the wine world. Who knows, one day a hybrid may take its rightful place in wine shops as “America’s grape,” and become a rising star in the international wine scene. Stay tuned!