Viticulture Notes

Vineyard and Winery Information Series:
Vol. 23 No. 2, May - June, 2008

Dr. Tony K. Wolf, Viticulture Extension Specialist, AHS Jr. Agricultural Research and Extension Center, Winchester, Virginia
vitis@vt.edu
http://faculty.vaes.vt.edu/vitis

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1. Canopy management workshop: 14 August 2008 – Save the date
2. Disease management reminders
3. Other seasonal reminders: 
4. Upcoming meetings

I. Canopy management workshop: 14 August 2008 – Save the date

The Virginia Vineyards Association’s annual summer technical meeting will be held on August 14th and will comprise a grapevine canopy management workshop to feature Dr. Richard Smart. Dr. Smart is internationally known for his viticulture research and vineyard consulting services. He is the senior author of Sunlight into Wine which has been the essential canopy management workbook for over 15 years. The August 14th meeting will be held at Veritas Vineyards (start) and Pollack Vineyards (conclusion) near Charlottesville.   More detail will be available on the VVA website (virginiavineyardsassociation.com) soon.

Dr. Smart will also be available for private vineyard consulting visits in Virginia on Friday, 15 August 2008.  Growers interested in this consulting should contact Dr. Smart directly at:

Dr Richard E Smart
Viticulture Consultant
PO Box 350 NEWSTEAD, Tas 7250, Australia email:  vinedoc@bigpond.net.au
web  www.smartvit.com.au   phone  +61 (0)3 6334 8838 cell  +61 (0)418 656 480 fax +61 (0)3 6331 0849

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II.Disease management reminders

• Vines are at or one or more weeks past full-bloom, depending upon variety and location within Virginia.  The pre-bloom through 4- to 6-weeks post-bloom period is the period of greatest concern for our most common and destructive fungal diseases -- powdery mildew, downy mildew, and black rot. Phomopsis inoculum discharge may also be expected to continue into the post-bloom period. Your ability to provide season-long management of these diseases is immensely improved if you keep the vineyard free of disease in this immediate post-bloom period.  Fail that task now and the balance of the season will be a very steep uphill battle.
  
  
• May 2008 was very similar to May of 2003 and 2004 – many wetting periods and excellent conditions for primary and repeating infections of the major diseases. Under conditions of repeated wetting, it’s helpful to use rainfast (locally systemic) materials to extend the protective period of applied fungicides.  Example, use Ridomil or phosphorous acid (e.g. ProPhyt, Phostrol or Rampart), or Tanos for downy mildew, Pristine or Quintec for powdery mildew and Elite or Rally for black rot.

Powdery mildew:

• Berries are extremely susceptible to infection from the start of bloom until about a month after fruit set.  Effective management through this period is critical. Initial outbreaks of powdery mildew are often observed on developing fruit clusters. This may result due to the susceptibility of clusters to infection, but is also likely due to the shaded, humid conditions within grapevine canopies that foster powdery mildew infections. Effective management starts by ensuring good ventilation and good sunlight penetration into the fruiting zone of canopies. This cannot be overstated.
  
  
• For highly susceptible varieties, use the most effective fungicides now (e.g., Quintec, Endura, or Pristine), but combine with sulfur on sulfur-tolerant varieties (to delay resistance development), or alternate with Rubigan or Topsin-M, or a potassium salt fungicide (e.g., Armicarb 100 or Kaligreen) on sulfur-sensitive varieties, again to lessen resistance development.
  
  
• Strobilurin fungicides (e.g., Abound, Flint, Sovran) may not be effective in your vineyard due to resistance development. Unlike sterol-inhibitors, where resistance development may give you some warning, the resistance to the strobilurins can be sudden and complete.

Downy mildew:

• Wet weather with temperatures in the 65 – 77 °F range set the stage for infections – typical night-time conditions now.
  
  
• Fungicides:  phosphorus acid (phosphite), captan and mancozeb, mefenoxam (Ridomil), copper, Gavel (Gavel is protectant only; no eradicant activity); also – some recently registered fungicides specific for downy are available (see below).
  
  
• Resistance to Qol (strobilurin) fungicides is documented in some VA vineyards and I don’t feel comfortable in recommending strobilurins alone for downy mildew control.
  
  
• Additionally, there are at least three “new” (recently registered) fungicides available that are exclusively effective against downy mildew and that increase the scope of tools that can be used to manage downy mildew. Revus, marketed by Syngenta, was discussed in the March-April 2008 Viticulture Notes. Tanos, which is a combination of famoxadone and cymoxanil is produced by DuPont. The Tanos label describes the fungicide as having both protectant and curative activities against downy mildew, but it must be mixed with a different resistance class of fungicide for resistance management. Presidio is a third newly registered, downy mildew-specific fungicide. Rainfast after 2 hours of drying, Presidio exhibits both eradicant and protectant properties according to the manufacturer (Valent); however, Presidio must also be tank-mixed with a fungicide from a distinctly different mode of action (resistance group) for downy mildew. Material application costs, rain-fastness, and eradicant activity will enter into the decision about what fungicide to use for downy mildew. A list of some of the downy mildew fungicides, their relative cost and usage notes, is shown in table 1.

Table 1. Costs, resistance group and usage notes for downy mildew fungicides (non-exhaustive list). 
Note: material costs shown are an approximate figure based on retail prices in Virginia, June 2008.

Black rot:

• Again, critical time is now, fruit develop resistance as they mature, but that’s some time off.
  
  
• Strobilurins (Abound, Sovran or Flint) or SIs (Rally or Elite) are all locally systemic (rainfast) materials, and good choices for this time of year. The sterol-inhibitors offer better eradication or post-infection eradication than they do protection. Conversely, the strobilurins provide longer protection than they do eradication or reach-back activity. Mancozeb and ziram are excellent and provide protection but not post-infection eradication. Pristine is a further alternative.

Botrytis:

• Rely primarily on your good canopy management to combat botrytis with most varieties.
  
  
• Use botrytis-specific fungicides only on botrytis-susceptible cultivars. Vangard, Elevate, Scala or Endura are currently effective fungicides, but each has limitations on the number of applications that can be made per year. Pristine is also reported as effective when used at the higher label rates (up to 23.0 oz/A, but applicators must have supplemental label and abide by 5-day REI if used at the highest – 23.0 oz/A -- rate).
  
  
• Apply a botrytis fungicide prior to cluster closing on susceptible varieties. Assess late-season (post-veraison) weather conditions and botrytis incidence in deciding whether additional sprays are necessary.

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III. Other seasonal reminders: 

• Canopy management: Shoot hedging of vigorous VSP-trained vines (and upper Smart-Dyson canopy) has commenced in most areas of the state. Remember to retain 15 or more leaves per shoot in doing any hedging. Tipping of downward-oriented shoots (GDC, Smart-Dyson, or Scott-Henry) can help avoid pinching shoots off the vine by passing vehicle tires.  Continue shoot positioning if needed – upright with VSP and follow-up downward combing with downward-oriented shoots of GDC, Smart-Dyson and Scott-Henry. Repeat the downward shoot combing if needed to facilitate the process – vinifera are more stubborn than American-type grapes, and may require additional positioning to develop downward-oriented canopies.
  
  
• Crop control: My general rule of thumb is to aim for about 1.5 to 2.0 pounds of crop per foot of canopy – the lower number for reds; the higher for whites. Again, this is a general rule and you may wish to further reduce those levels if your own situation and experience warrant the reductions. With vigorous vines (if you’re hedging shoots now, they’re vigorous) wait until July (but prior to veraison) to effect further crop reduction, otherwise vines will compensate with larger berries and more compact clusters. With low-vigor and/or young vines, remove additional crop soon after fruit set (now), once you can see the extent of set. Remove all clusters from stunted shoots (e.g., those that appear to have aborted shoot tips and that are less than 18 inches long). Basal clusters are typically the larger(est) clusters on shoots that bear 2 or more clusters. Deciding which cluster(s) to remove on a shoot has more to do with proximity to other clusters than to position on the shoot though. We prefer to thin clusters with the strategy of minimizing cluster-to-cluster contact, or contact of the cluster with trellis hardware or cordons, rather than following a particular prescription for basal cluster versus more distal cluster removal.  Clusters and berries that freely develop without contact with other objects tend to be freer of fruit rots and exhibit more uniform berry ripening than do clusters that are contacting trellis or grapevine parts.
  
  
• Nutrition: It’s not too late to collect bloom-time petioles for plant tissue analysis (see directions at my website: http://faculty.vaes.vt.edu/vitis.  Click on “Grapevine Petiole Sampling Instructions”). Small rates (20 to 30 pounds actual N/acre) of nitrogen can be applied shortly after bloom to carry vines through harvest if N was low in previous years. Make sure that applied nutrients are incorporated, as by cultivation or rainfall. Soil-applied nutrients will be unavailable to the plant unless there’s sufficient incorporation and soil moisture to get the nutrients to the roots. Don’t apply what’s not needed. Use plant tissue analysis, soil testing, and visual observation to determine nutrient needs; not commercial salesmanship. We continue to recommend either the Penn State plant analysis lab or A&L Eastern Laboratories for submission of plant tissue analyses.
  
  IMPORTANT:  You can submit plant tissue samples directly to these labs with the appropriate submission forms:  Penn State plant analysis forms are available at: http://www.aasl.psu.edu/. Click on “submitting samples” on the menu on the left-hand side of screen.  A&L Eastern Laboratories also has submittal forms for plant tissue samples at their website (http://www.al-labs-eastern.com/agricultural.html). We will provide feedback to you on tissue analysis results if desired, but you will need to contact us (vitis@vt.edu) and request the recommendation once you receive your lab results.
  
  
• Insects: Scout for grape berry moth infestation in developing grape clusters. Insecticide options, if warranted, are in the PMG (http://www.ext.vt.edu/pubs/pmg/hf3.pdf). I’ve had a number of calls this past month about tomato tumid galls, which appear as pea- to marble-sized, often reddish galls on shoot stems, cluster rachises and sometime leaf petioles.  These and similar galls, some more conical in appearance are tissue overgrowths caused by egg-laying of small insects (midges). They are entirely benign and unless you have a very unusual situation, they do not warrant removal or other control measure. Enjoy them for the biotic diversity that they represent. Aerial phylloxera becomes apparent at this time of year on some varieties (esp. some hybrids) and may warrant insecticidal control if historically severe (see the PMG). Japanese beetles can be expected to make their appearance within the next couple of weeks. Control is often warranted to avoid excessive defoliation by Japanese beetles and a number of insecticide options are found in the PMG.
  
  
• Other threats: Hail hits at least one VA vineyard per year and injury can range from the occasional torn leaf and bruised berries (almost always on the exposed portion of the cluster) to dings on shoot stems and even defoliated vines. The minor symptoms may be difficult to trace to hail, while there is no mystery about the latter. There’s not a lot you can do after a catastrophic hail storm. The vines will usually grow back out. Damage to fruit (bruises, sunken regions on the berry, exposed seeds, etc.) may lead to disease if the weather remains wet, but these injuries usually dry up with pre-veraison berries. A botrytis-specific fungicide might be warranted with botrytis-susceptible varieties that have been hit by hail.

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IV. Upcoming meetings

1. Vineyard meetings in Virginia

Vineyard meetings, arranged by Virginia Cooperative Extension Agents, were planned for the period from April through July. The meetings generally include one to several grape specialists with Virginia Tech and the agents may provide presentations as well. Most meetings include an overview of the vineyard activities by the owner/operator of the host vineyard. The following meetings are scheduled for the remainder of this season.

Vineyard Meetings are scheduled for the following dates from 11:00 am – ~ 2:00 pm.  The first hour will be a tour of the vineyard, followed by a lunch discussion.  Everyone is asked to bring a bag lunch. Presentation topics may be modified slightly depending upon unique seasonal issues.

More information can be obtained from:
Kenner Love
Rappahannock County Cooperative Extension
klove@vt.edu  (540) 675-3619

American Society of Enology and Viticulture, Eastern Section annual meeting:
July 14-16, 2008
St. Catharines, Ontario

The 2008 ASEV/ES meeting will take place 14 to 16 July 2008 at the Four Points by Sheraton St. Catharines Niagara Suites, in the heart of the Niagara Region in Ontario. This all-suites hotel is just minutes from Niagara Falls, Niagara-on-the Lake, Welland, and Fort Erie. The conference will kick off with an all-day tour on Monday the 14th that will start in Niagara-on-the-Lake with visits in the morning to Lambert Vineyard, then onto Southbrook Winery including a tour of their organic and biodynamic vineyard followed by a tour of a true gravity flow system at Stratus Winery and tasting of their assemblage wines. Lunch will follow at picturesque Hernder Estate Wines in West St. Catharines. The afternoon will include a tour of family run Fielding Estate Winery along the beautiful Niagara Escarpment on the Beamsville Bench and end with a tour, tasting and barbeque at Creekside Estate Winery in Jordan, home of the 2008 Ontario Winemakers of the Year Craig McDonald and Rob Power. Research presentations will occur on the 15th and 16th, and include a symposium on aromatic white varieties. The final day will conclude in the evening with a Farewell Reception and grazing-style dinner, intended to introduce delegates to a half-day tasting conference that will take place just across the street at Brock University on Thursday July 17. The conference on 17 July, entitled "The Riesling Experience", will include technical talks from regional and international experts, tastings, and a gourmet lunch with plenty of great food. It is our hope that attendees to the ASEV/ES will also take advantage of this special opportunity to attend The Riesling Experience immediately following the ASEV/ES meeting.  You do not have to be a member of the ASEV/ES to attend the meeting, although registration costs are lower for members. Program details, including presentation titles and speakers can be found at: http://www.nysaes.cornell.edu/fst/asev/conference.php.

Pennsylvania Canopy Management Workshop (August 12, 2008)

If you can’t attend the canopy management workshop in Virginia (see page 1), Dr. Richard Smart will be presenting a similar workshop earlier in the week in Lancaster County, Pennsylvania that might suit your travel plans better.  Please contact Mark Chien for registration details: Mark L. Chien
Wine Grape Educator, Penn State University    Tel: 717-394-6851     mlc12@psu.edu 

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