Viticulture Notes

Vineyard and Winery Information Series:
Vol. 19 No. 2, March-April 2004

Dr. Tony K. Wolf, Viticulture Extension Specialist

Table of Contents

I. Current situation

The extent and nature of the observed injury is somewhat puzzling. The low temperatures measured or estimated from nearby min/max thermometers during the 2003-2004 winter were generally at or above 0°F, with the lowest temperatures occurring around 10 January. Given the general pattern of winter temperatures - not a great deal of fluctuation in mid-winter - and our own measures of bud cold hardiness (reported in Jan-Feb Viticulture Notes), I would not have expected much problem with temperatures at or above 0°F in January; at least not with generally well managed vines in normal years. In some of the affected vineyards, varieties that we recognize as relatively cold-tender were the most severely affected. For example, one vineyard that grew a range of varieties only showed significant amounts of injury in older Syrah and Tannat vines, and injury in the latter was only observed in those sections of rows that dipped into a low point of the vineyard topography (cold air ponding). Cabernet Sauvignon and Merlot were also affected in some vineyards, with both cane and trunk injury apparent. Riesling, which we consider to be a relatively cold-hardy vinifera variety, also showed significant trunk injury in one Fauquier County vineyard. In most cases, the injury was not observed until March of this year, even though some rough pruning had been done in January and February.

Examination of split trunks in two separate vineyards revealed brown, desiccated wood. In other cases the injured trunks were hydrated and oozed moisture when shallow cuts were made into the trunk to examine the status of the phloem and cambial (regenerative) tissues immediately beneath the bark. In the former situation, the extent of browning and desiccation suggested that the trunk injury may well have occurred during the previous (2002-2003) winter, but perhaps went unrecognized due to abundant moisture during the 2003 growing season. Canes on some of these vines were observed to be drying out in March of 2004, but the drying (and browning) appeared to radiate out from the cordon. Trunk splitting is thought to occur either from excess water freezing in the trunks causing a physical strain, or from uneven drying of the wood. But more commonly, the drying and cracking of injured wood occurs in the winter following injury, when drier atmospheric conditions prevail. Bob Pool, viticulturist at Cornell University's experiment station in Geneva, NY, has a relevant discussion of bud, cane and trunk injury (and trunk splitting) at his web site: (www.nysaes.cornell.edu/hort/faculty/pool/trunkinjury/tihtml/trkinjtablecontents.html), including some good photographs of injury to these various organs. Dr. Martin Goffinet, also of Cornell University, has a very detailed and illustrated article, "Anatomy of Winter Injury and Recovery" recently posted at the following site that is also well worth spending some time reviewing: (www.nysaes.cornell.edu/hort/faculty/goffinet/AnatomyWinterInjury.pdf

Some of the other cases of injury observed in Virginia, including splitting trunks, came from vineyards where the injury appeared to be localized in regions of the vineyard that experienced poor soil water drainage. It may be that in these cases the affected vines did not acclimate well to winter temperatures due to saturated soil conditions.

Whether the injury occurred during the 2002-2003 winter, or in the 2003-2004 winter, is of academic interest at this point. The affected growers must compensate and respond to the injury in either case. Vines with split trunks will have to be retrained from the graft union up, assuming there are live, latent buds in the graft region of the scion. Shoots that do develop from such vines will likely be extremely vigorous because they are supported by a large, intact root system. Permit these vines to develop as many shoots as reasonably possible, and keep the shoots well exposed and supported upright on the trellis system to minimize shading and to permit effective disease management. The observed injury that I observed was not uniform across entire vineyard blocks and you may find that uninjured vines (or uninjured trunks on multiply-trunked vines) have more shoots than can be trellised. So be prepared to do some shoot (and crop) thinning where needed in June and July. Where injury is certain and significant, avoid fertilization and consider sowing a cereal (or allow weed growth) under the trellis to sap some of the moisture and nutrients from the vines to moderate the expected vigorous shoot growth. Retain moderate (1/2-inch to 5/8ths -inch diameter) canes next winter to retrain trunks and cordons. You might also want to protect these shoots against cicada egg-laying (see next section) if you are in a cicada emergence area.

For all readers, I would encourage you to do some bud, cane and trunk checks for injury even as we are at or approaching bud-break. Based on the above, I suspect that some trunk injury that occurred during the 2002-2003 winter went unrecognized last year. There is substantial injury to vineyards north of Virginia due to low temperatures in January 2004. Unfortunately, some of these regions have seen two bad winters in a row now. We'll learn the full extent of this injury during the coming months.

The appearance of cold-injured trunks is a reminder that we are growing cold-tender grapes in a region where winter temperatures can be marginally acceptable. Drought (2002), excess rain (2003), or early fall frosts (October 2003) can reduce vine cold acclimation and mid-winter cold hardiness, further increasing the potential for severe injury. Many growers, particularly those who have entered the industry since 1996, have ignored multiple-trunking recommendations and some have planted some very cold-tender varieties. These can be calculated, acceptable risks with small plantings in excellent sites, but the hazards are real and should be carefully considered for future. Vineyard site and variety recommendations can be found at: http://arecs.vaes.vt.edu/arec.cfm?webname=winchester§ion=about_us&subsection=4356&PID=vitis

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II. PERIODICAL CICADAS:

The emergence of periodical or 17-year cicadas will occur over parts of northern Virginia in May/June 2004 (www.ext.vt.edu/pubs/entomology/444-276/444-276.html). The emergence of periodical cicadas varies throughout the state, depending upon the specific brood. "Brood X", as the northern Virginia brood is referred to, last appeared as adults in 1987. Readers in parts of southwest Virginia witnessed the emergence of the brood IX 17-year cicada in 2003, while growers in central Albemarle County saw brood II emergence there in 1996. Northern Shenandoah County had an emergence (Brood V) in 1999. Doug Pfeiffer, Virginia Tech's grape entomologist, provided the following information (www.ento.vt.edu/Fruitfiles/cicada.html):

Biology: Periodical cicada spends most of its life as a nymph, feeding on xylem sap from tree roots. In the final year of development, nymphs crawl from the soil, climbing tree trunks or any other structure. During the night, the nymphal skin splits along the midline, and the adult emerges. Adults appear in mid- to late-May (a few individuals may be heard as early as late-April). They appear around sunset, males slightly preceding females. Males congregate en masse in "chorusing centers". Singing peaks around 10:00 AM. Adults feed on a wide range of woody plants during the day; such feeding is apparently restricted to the females because the male digestive tract is rudimentary. Oviposition (egg laying) begins about 2 weeks after emergence. Eggs are inserted into twigs in groups of 10-25; the slit into which the eggs are inserted is 1-4 inches (2.5-10 cm) long. Females may lay over 500 eggs. Oviposition peaks in the early afternoon. Adults are active for about 6 weeks. Eggs hatch 6-10 weeks after oviposition, whereupon nymphs leave the twigs and drop to the soil. Nymphs tunnel to the roots where they establish themselves for feeding.

What threat do cicadas pose to grapevines? Injury by egg-laying is a much greater problem than is the feeding, and injury to young (one- and two-year-old) vines is more significant than is injury to older, mature vines. The cicadas will deposit eggs in grape shoots and smaller cordons of the vine. Unsupported shoots often break beyond the point of egg-laying, but because this occurs relatively early in the growing season (June), lateral regrowth will normally compensate for the loss of a primary shoot tip. In older wood, the oviposition site typically heals without apparent long-term consequence. The damage to shoots on newly planted vines, however, may render the shoots and developing canes unfit for retention as permanent trunks (or cordons), and one southwest Virginia grower reported actual vine loss due to cicada injury during 2003.

Insecticidal control of cicadas is not very practical because of the extended period of emergence and activity (up to 6 weeks) and because insecticides would have to be applied very frequently to come in contact with newly emerging insects. Netting is an option (see suppliers listed below), but the economics of this approach with grapevines is questionable. Young (first-year) vines are a special consideration in that one is attempting to produce shoots to serve as trunks in the following year. One means of protecting the shoots of young vines would be to use grow tubes, which would discourage cicadas from at least the first 24 to 36 inches of the shoot, depending upon the height of the tube.

Sources of netting for cicada exclusion

Tipper Tie	Roxford Fordell	Marcus-James Company
West Chicago IL 60185	Greenville SC & Los Angles, CA	DeSoto MO 63020
800-736-0990 or 630-293-3737	800-426-4690	636-586-6238
www.tippertie.com/netting.asp	www.roxford.com	www.marcus-james.com

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III. 2004 EASTERN UNITED STATES WINEGRAPE FUNGICIDE GUIDE

Information on the Guide is offered here as a public service, not as a commercial endorsement. In my experience, it is disease management that most significantly challenges both the neophyte and the experienced producer in overall pest management. The number of fungicides available to growers is both an asset and a technical challenge to understand their appropriate uses. The Fungicide Guide helps organize the information, allows a rough cost comparison of control options, and assists with regulatory compliance.

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IV. QUESTION FROM THE FIELD:

A: I asked Dr. Wayne Wilcox (Cornell University) about the phosphorous acid products (also termed phosphite and phosphonate). His recommendations for 2004, based in part on experiments conducted in 2003 (and before) appear in the current issue of Wine East magazine. Using ProPhyte on varieties that are relatively susceptible to downy mildew, Dr. Wilcox obtained "substantial protective and postinfection activity on foliage", but the protective activity declined in older leaves, particularly between 3 to 7 days before an infection. Nevertheless, ProPhyte continued to suppress spore production from established lesions for at least 7 days. "Sporulation was reduced by 95-100% on most leaves in most treatments, and by approximately 85% in the others". ProPhyte also offered post-infection ("kick-back") activity for young leaves (up to the third unfolded leaf from the shoot tip). Based on his work, Dr. Wilcox suggested that a 14-day schedule was too long under high downy mildew pressure conditions - at least for protection against fruit infections. While he didn't suggest a tolerable interval, his data might suggest somewhere around 10 days as a starting point, and this might be extended in mid- to late-summer when the greater threat is to foliage, rather than fruit/rachis infections (my interpretation of Dr. Wilcox's data and comments). We used ProPhyte in our research vineyard at Winchester on 5 occasions during 2003, including consecutive sprays on 25 July, 5 August, and 15 August (September - October, 2003 Viticulture Notes). We did not have downy mildew. We will likely again use ProPhyte or other phosphorous acid products in 2004, although I would be reluctant to rely entirely upon them during the bloom / 2-week post-bloom period if that period is again rainy.

As a reminder, do be careful not to exceed the label rate of any of the phosphorous acid / phosphite products. We experienced some foliar burn (reported electronically via my GrapeNews listserv on 14 August 2003) when we tank mixed a high rate (err on our part - double label rate) of ProPhyte with a rate of 6 pounds of sulfur / acre (temperatures in high eighties at time of application [5 August]). The phytotoxicity may well have been due to the inadvertent doubling of the ProPhyte application rate, rather than the sulfur - something we'll try to examine in 2004.

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V. UPCOMING MEETINGS (VIRGINIA AND REGIONAL):

27-28 Pennsylvania Wine Association Annual Meeting. Blair County Convention Center and Courtyard Marriott Hotel. Altoona, PA. Mr. Angelo Pavan of Cave Spring Cellars in Ontario will discuss the Ontario Vintners Quality Alliance. Various topics on wine making and marketing and viticulture. http://www.pennsylvaniawine.com/.

May
12 Virginia Summer Meeting Series. Pearmund Cellars Vineyard Winery. Chris Pearmun, owner. 10 a.m. to 2 p.m. First hour is tour of vineyard. Topics - Nutrition Considerations, Canopy Management (shoot thinning), Upcoming ASEV/ES Meeting, and Seasonal Disease Control Considerations. VA Tech Viticulturist, Dr. Tony Wolf. Grape Berry Moth and Other Insect Issues: Product Labels and Environmental Precautions. VA Tech Entomologist, Dr. Doug Pfeiffer. Bring a bag lunch. For information please contact the Rappahannock Extension Office at (540) 675-3619.

13-14 Vineyard Soils in the Eastern U.S: Sponsored by Penn State Cooperative Extension. Yves Herody, well known geologist from France and Paul Skinner, owner of Terra Spase in Napa Valley will lend their perspective to the matter of Eastern terroir. A two-day meeting will include one day of lecture and a day out in the field splitting rocks. This workshop will offer a geologists view of vineyard and viticulture as well as vineyard soil analysis. Dates are to be determined. For more information, contact Mark Chien.

June
6 Winery Planning and Design Workshop. A one-day workshop at Penn State University, State College, PA. This program is for those seriously interested in entering the commercial wine industry. This event is being coordinated by Dr. Bruce Zoecklein, Head, Enology-Grape Chemistry Group, Virginia Tech, and Dr. Stephen Menke, Enology Extension Educator, Penn State, and is co-sponsored by Virginia Tech and Penn State. The workshop will include presentations, discussions, and printed materials on the following: business plan, economics of wine production, winery design, equipment, refrigeration, sanitation, lighting, electrical, water and waste requirements, gravity flow, caves and expansion needs, government compliance. The workshop fee is $300, payable to Penn State. Send check to Mid-Atlantic Winery Planning and Design Workshop, c/o Stephen Menke, Adams County Extension Office, 670 Old Harrisburg Road, Gettysburg, PA., 17325-3404. Pre-registration is required and enrollment capacity is limited. The registration deadline is May 21, 2004.

12 Maryland Grape Growers Association Summer Field Day. Location to be announced. Tony Wolf is the invited speaker. Check the MGGA website or contact Bob White, chair of the research committee.

19/20 Grapegrowing Seminars at Linden Vineyards June 2004. Nuts and bolts sessions for home or professional grape growers. First day covers vineyard establishment. Day 2 covers vineyard canopy management. Seminars will be held at Linden from 10:30 a.m. to 4:00 p.m. The cost is $75 per person, per day. Bread, cheese and sausage are available for purchase at Linden for lunch. Register by phone at least one week in advance. Space is limited. 540.364.1997

21-25 Seventh International Symposium on Grapevine Physiology and Biotechnology. UC Davis. Topics include photosynthesis, respiration and carbon relations, water and nutrient relations, stress physiology, temperature responses, cold hardiness physiology, fruit development, genetics and molecular biology. Tentative workshops include climate change and the vine and an update on the International Grape Genome Program. Information at http://grapevinephysiologysymposium.uckac.edu/default.htm.

30-7/2 American Society for Enology and Viticulture National Annual Meeting. Manchester Grand Hyatt Hotel. San Diego, CA. The 2004 Annual Meeting will feature a variety of presentations representing the latest in research in enology and viticulture. The program will also include invited keynote speakers from around the globe. The 55th ASEV Annual Meeting will include a full trade show and enology and viticulture poster sessions. The Annual Meeting includes a special Brett session and will be preceded by our Soil Environment and Vine Nutrition Symposium. http://www.asev.org/.

July
14-16 American Society for Enology and Viticulture Eastern Section Annual Meeting. Roanoke Hotel, Roanoke, VA. Symposium title is Grapes, Wine and the Environment. The focus will be on growing wine in a humid climate with emphasis on soils, mesoclimate and wine production. Outstanding guest speakers on the program. Technical sessions will feature regional research and projects funded by the Viticulture Consortium:East. A pre-conference tour of vineyards in southwest Virginia will be offered on 13 July. www.nysaes.cornell.edu/fst/faculty/henick/asev/

21 Virginia Summer Meeting Series. Horton Vineyard (town of Orange), Dennis and Sharon Horton. 10 a.m. to 2 p.m. First hour is tour of vineyard. Topics - Grape Root Borer and other Insect Issues: Product Labels & Environmental Precautions. VA Tech Entomologist, Dr. Doug Pfeiffer. Crop Estimation and Use of Mid-Season Average Cluster Weight Data to Refine Harvest Estimate. VA Tech Viticulturist, Dr. Tony Wolf. Bring a bag lunch. For information please contact the Rappahannock Extension Office at (540) 675-3619.

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"Viticulture Notes" is a bi-monthly newsletter issued by Dr. Tony K. Wolf, Viticulture Extension Specialist with Virginia Tech's Alson H. Smith, Agricultural Research and Extension Center in Winchester, Virginia. If you would like to receive "Viticulture Notes" as well as Dr. Bruce Zoecklein's "Vinter's Corner" by mail, contact Dr. Wolf at:

Dr. Tony K. Wolf
AHS Agricultural Research and Extension Center
595 Laurel Grove Road
Winchester, VA 22602

or e-mail: vitis@vt.edu

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