Vineyard and Winery Information Series:
Vol. 21 No. 4, July-August 2006
Dr. Tony K. Wolf, Viticulture Extension Specialist.
Last-minute reminder: The Virginia Vineyards Association’s Summer Technical Meeting will be held Thursday, 3 August 2006 at Chrysalis Vineyards, Middleburg. Please see the VVA’s web site (http://www.virginiavineyardsassociation.com/events.htm) for meeting registration and program agenda.
Each year brings its own collection of oddities and unusual observations. Two thousand and six has been no different. The following are a few of the notebook items for 2006 from our own vineyard and from our vineyard visits.
We heard several complaints of poor fruit set in June, particularly in areas south of the James River and in Southeast Virginia. A search for a commonality to those problems led us to conclude that the most likely cause for some of the problems was hot, dry weather during bloom. Flower clusters were present on the vines in question - they just did not set the normal amount of berries. The presence of flower clusters was evidence that conditions during the previous (2005) season were conducive to flower cluster formation. While cool, wet weather during bloom is often the cause of poor set, other stresses can also decrease fruit set. We can speculate about several things that could have had a bearing on the fruit set problem, with some general areas being temperature, nutritional, and moisture. Drought or temperature extremes can reduce the vine’s ability to produce new energy through photosynthesis. The pre-bloom period coincides with a nadir of carbohydrates as the vine has expended much of its stored energy in new shoot production. Carbohydrates are needed for fruit set and initial fruit development. If the vine is at a carbohydrate deficit during bloom, reduced fruit set could be anticipated. It’s tempting to think only of the current season when trying to diagnose a problem like poor fruit-set. But the post-harvest conditions of the preceding year might also have had a bearing on the fruit-set issues of 2006. If the vines were not in good physiological condition going into the 2005-2006 winter – if they had low carbohydrate reserves – a range of symptoms could be expected in spring 2006, including poor bud-break, reduced shoot growth, and poor fruit set. In at least some of the fruit set problem vineyards of 2006, shoot growth was adequate if not overly vigorous. Thus, the comment about the preceding fall carbohydrate levels is not suggested as a universal cause or feature of problems observed at fruit set; just something to consider.
Coincidentally, we were made aware of investigations of the role of molybdenum on fruit set in Australian studies during a visit by Dr. Peter Dry of the University of Adelaide. Mo is an essential plant nutrient, but we don’t pay much attention to it, partly because the critical levels are very low (1 to 3 ppm) and partly because the routine analytical ability to detect Mo is not very sensitive. Several recent studies in Australia have shown that low Mo levels can be a contributing factor to the Millerandage or “Hens and Chicks” condition recognized as small, shot berries borne on the same cluster with normal-sized berries. This problem is especially prevalent in some years with Merlot. The Australian work (Williams et al., 2004) got us thinking that we don’t really know what our Mo levels are in Virginia vines. While we don’t have any reason to suspect a problem with Mo deficiency, we are really pretty ignorant about what the levels are. Fritz Westover has begun having some plant tissue samples that were submitted this spring resubmitted and tested for Mo. It’s too early to reach any conclusions, but we have been surprised at how low some of the grape samples have been in Mo concentration. We’ll review our findings in a future VN.
We had a number of calls from vineyards in early July about berry splitting following heavy rains. One northern Virginia vineyard reported that nearly 10% of berries on almost every cluster were splitting, with the cracks spiraling down from the pedicel or running longitudinally. We often see some splitting following hail storms, but in this case the splitting occurred on all sides of the clusters, not just the windward side. The other odd feature of this splitting was occurrence at an early stage of berry development – we’ve all seen berry splitting with rains near harvest, but splitting at the pea-size or smaller stage of development is much less common. The fact that the berry splitting occurred immediately after the onset of heavy rains, following an extended dry period, suggests that internal berry water pressures had a direct bearing on the cracking. The cracks extended deep into the mesocarp of the berry, rather than being restricted to the epidermis as often occurs post-veraison. Again, this is more an observation and a suggestion of potential cause. One final comment: cracking or other berry damage that occurs pre-veraison has far less impact on the cluster than does cracking that occurs post-veraison. If dry weather follows the early cracking, the affected berries often continue to develop, or they desiccate and are shed from the cluster. Later (post-veraison) damage, as we know, often supports microbial growth which in turn can lead to extensive, non-specific bunch rot problems.
Figure 1. Ruprestris speckle symptoms on Chambourcin leaf, 15 June 2006. Courtesy Alison Bremner.
We looked at “Rupestris speckle” on Chambourcin in a vineyard in June and I include here a photo of this disorder (Figure 1). This physiological (apparently not caused by a biological agent or pathogen) disorder is a heritable trait with vines that have V. rupestris parentage. It occurs in a number of varieties, including Chambourcin and the recently named Valvin Muscat, released in July 2006 from the New York State Agricultural Experiment Station (http://www.nysaes.cornell.edu/pubs/press/current/060707Grapes.html). The occurrence of the leaf spotting is not believed to affect grape yields or quality (Grape Disease Compendium, 1988), but does appear to be more pronounced under stress conditions, especially over-cropping, nitrogen deficit, and drought. All three conditions existed to some degree in the vineyard in which the photo in Figure 1 was taken. There are no particular “control” recommendations, just avoid stresses that make the speckle symptoms more apparent.We had several calls of hail damage in mid-July and there were, no doubt, many unreported episodes. Hail damage is not unusual in Virginia and some vineyards are routinely affected more than are others, but it’s often a random act. The question is what to do about it once it occurs. See our comments, below, on possible post-damage actions that can be followed.
Considine, J.A. 1981. Correlation of resistance to physical stress with fruit structure in the grape Vitis vinifera L. Australian Journal of Botany 29:475-482.
Pearson, R.C. and A.C. Goheen. 1988. Compendium of Grape Diseases. APS Press, St. Paul, MN. 93 p.
Williams, C.M.J., N.A. Maier, and L. Bartlett. 2004. Effect of molybdenum foliar sprays on yield, berry size, seed formation, and petiolar nutrient composition of ‘Merlot’ grapevines. J. Plant Nutrition. 27:1891-1916.
Hail injury: Recently we have been getting questions from the field regarding hail damage. Hail damage can be extensive, with near defoliation of the affected vines. In other cases the grower might not realize that a storm cell contained hailstones, and might not recognize the symptoms of hail injury. Berries will be bruised or cracked, predominantly on the windward side of the cluster and vine canopy. Leaves will have tears that may or may not extend to the leaf edges, and shoot stems may also bear bruises or sunken spots where the hail stones hit. There’s not much that can be done with the damaged fruit; however, the remaining crop and leaf area must be protected. New leaf area will eventually replace that which is lost. The greater issue is the injured fruit. Application of a broad-spectrum fungicide like Topsin-M or captan may help avoid opportunistic fungi, including Botrytis, that can affect damaged tissue. A botrytis-specific fungicide may be helpful as well; Elevate, Vangard, Scala, or the highest label rate of Pristine would be suitable choices. If the damage occurred pre-veraison, the injured berries may scar over and continue developing, or they may be shed without the onset of fruit rot. Damage to post-veraison berries is more traumatic and will most likely promote fruit rot. The best to hope for is dry weather to dry up injured berries. However, you can increase sunlight penetration and improve air circulation by selective leaf-pulling from around damaged clusters, being conscientious to remove leaves touching fruit clusters.
Other disease issues: If you’ve done a good job of powdery mildew (PM) control, you may be able to relax at bit at this point. Berries are less susceptible to powdery mildew infection after they attain 8° Brix. Fruit may, however, continue to show fungal development from infections that occurred up to one month ago, and low levels of PM may exist on fruit even with apparent “good” prevention programs. In actuality relax means continue to maintain a prudent mildew prevention program. However, options for powdery mildew fungicides in the pre-harvest period are constrained by label pre-harvest intervals (PHIs) and sulfur application should be avoided within 6 weeks of harvest to reduce sulfide production and off-odors in wine. Historically options for powdery mildew control during this period have been strobilurins and sterol-inhibitors due to their 14-day PHI; however, we are concerned with resistance development with strobilurins and sterol-inhibitors (refer back to May 2006 Viticulture Notes for information on resistance to strobilurins and sterol-inhibitors). Quintec, with a 14-day PHI, remains a preventative option; however, Quintec should be applied no more than 3 times per season. Several powdery mildew eradicating fungicides are also available, including Armicarb 100 or Kaligreen (potassium bicarbonate), OxiDate (hydrogen peroxide), and Nutrol (monopotassium phosphate). These products are short-lived but used on a 7-day basis, appear to effectively control PM. The biocontrol product, Serenade (Bacillus subtilis) is another option. Oils, such as JMS stylet oil, are also effective for powdery mildew eradication if used with at least 100 gallons of water per acre. The downside to oils is a delay in sugar accumulation in treated fruit due to temporarily reducing photosynthesis.
Favorable conditions for downy mildew (DM) development are common in Virginia from now until approximately mid-October. Scout young leaves (such as on laterals) for late-season DM infection. To avoid potential defoliation continue to use a downy mildew protectant fungicide such as Captan or Captec (0 day PHI, 3-4 day restricted entry interval). Captan will also provided control of the fruit rot phase of Phomopsis, black rot, and the late-season rots (see March 2006 Viticulture Notes). Phosphorous acid products are another excellent option for downy mildew control with both eradicant (3-4 days back-reaching) and protectant activity (6-7 days forward protection). Due to wine-making concerns, copper use is discouraged in the 6 weeks prior to harvest; however, copper would be a suitable post-harvest material with varieties that are not copper-sensitive. Mancozeb (e.g., Penncozeb, Manzate, etc.) would be an option on young or non-fruiting vines, as well as post-harvest treatment for downy mildew.
Field trials conducted by Wayne Wilcox at Cornell University found better Botrytis control is achieved when Botrytis materials, Vangard, Scala, or Elevate, were sprayed at bloom, bunch-closure, veraison, and 2-weeks later. Pristine at higher rates and Endura also offer some Botrytis protection. Fruit cluster coverage is critical with Botrytis materials, so use sufficient gallonage per acre. Culturally, the incidence of Botrytis can be reduced by removing leaves that are directly touching clusters, and opening the eastern side of N/S-oriented rows. It is not too late to do some follow-up leaf pulling in Botrytis-prone cultivars (e.g. Chardonnay and Seyval), but avoid pulling too many leaves that could cause sun-burning of fruit.
One more word of caution: Avoid sulfur and copper fungicides within 30 to 45 days of harvest with varieties harvested for wine-making and be continuously aware of pre-harvest intervals.
Post-harvest disease management focuses on management of foliar powdery and downy mildew until frost. All materials are back in the game once harvest is complete so use the cheapest materials for the job. Inexpensive options are copper (excellent DM, fair PM control), post-harvest oil (good PM control), sulfur (good PM control), and mancozeb (excellent DM control).
HELP WANTED: Warmer winter temperatures over the past few years have caused us to suspect a shift in areas of the state where Pierce’s Disease is present. We are interested in “mapping” the incidence of Pierce’s Disease in Virginia with the short-term goal of determining the precise areas of Virginia where this disease is occurring. If you believe you have Pierce’s Disease or have seen suspicious symptoms, please contact me directly via e-mail (firstname.lastname@example.org) or phone (540-869-2560 x 23). For information on Pierce’s Disease and symptom pictures visit the online publication “Pierce’s Disease of grapevines” at http://arecs.vaes.vt.edu/webinfo/files/PD2.pdf.
Fritz Westover Viticulture Research/Extension Associate.
The World Congress of Soil Science (WCSS) was held at the Pennsylvania Convention Center in Philadelphia from July 9-15th. It has been 46 years since the congress was last held in the US, so we were fortunate to have such a prestigious international scientific event right here in the Mid-Atlantic. The session topics were vast, as one would imagine, and included areas such as soil and environment, sustaining soils, food and fiber production, soil contamination, specialty crops, and soil microbial interactions and biodiversity, to capture a few.
I was encouraged to find that viticulture dominated the theater for “Soil, Wine and Other Quality Crops”. The group of soil and wine researchers encompassed a wide range of scientific disciplines including geology, pedology, viticulture, and agronomy. Session moderator Dr. Edoardo Costantini of the Experimental Institute for the Study of Soil Conservation (ISSDS) Florence, Italy, expressed a strong interest in continuing to promote sessions on soils and wine in future WCSS conferences. The session was just over two hours in length, which was not nearly enough to deconstruct the mystery of vineyard soils. Some of the session highlights are reviewed here.
There is no simple recipe to describe the ideal soil for producing the best quality wines. Even if one did find a few key parameters (such as well-drained and moderate nutrient holding capacity here in the East) it is not as simple as mixing a set quantity of silt, sand, clay, and organic matter to create a soil class. Soils are the product of thousands of years of chemical and physical weathering processes and are very much a product of parent (rock) material and climate.The word “terroir”, which is all-encompassing of the climate, geology, and soil components that describe the place in which a wine derives its own unique character, was not the focus of the
talks at the WCSS. Instead, a focus remained on the specific attributes of just one parameter of terroir- the soil. The ultimate goal of such understanding is not only to associate a particular soil profile with a wine character, but also to map out the diversity of a soil in a vineyard block in order to micro-manage a vineyard in a way that fully expresses its native soil character. To do this, a grower must attempt to fully understand the soil characteristics in his or her blocks and manage them accordingly. The end goal may be to manage a block in order to achieve uniform ripening or to develop an understanding of those differences within a block and harvest and ferment sub-blocks separately in an attempt to isolate those differences.
The underlying theme of most viticulture talks at the WCSS was the concept of vineyard micro-management known as “precision viticulture”. The term “precision agriculture” or more specifically “precision viticulture” has become somewhat of a buzz-word in the viticulture industry. Precision agriculture is defined by the US Congress as “an integrated and production based farming system that is designed to increase long term, site-specific and whole farm production efficiencies, productivity and profitability while minimizing unintended impacts on wildlife and the environment". The first step for the producer using this system is to determine the variability within their fields by relating crop production and/or soil attribute data to geographic coordinates using a Global Positioning System receiver (GPS) and organizing the data into software mapping programs known as Geographic Information Systems (GIS). These data become the basis for digital soil fertility and variability mapping of factors including soil pH, nutrient content, water holding capacity, and depth to bedrock. The objective of precision agriculture is to quantify and manage spatial and temporal variability that exists in virtually every field. Rather than applying fertilizer, pesticides, or water at a uniform rate across an entire field, growers use computer technologies to continually adjust their input applications as they operate their equipment based on the biophysical variability of their land. For perennial crops such as grapes, the system can become even more in-depth, including seasonal plant growth parameters such as yields per vine or dormant pruning weights, and visual observations, which can then be related to wine quality.
Several of the presenters at the WCSS described their techniques to quantify soil attributes and some had advanced their work beyond the vineyard and into the wine lab. Below are a few notes on each of those presentations combined with details from the author’s abstracts.
Jean-Jacques Lambert, Department of Viticulture and Enology, UC Davis, remarked that soil spatial variability in vineyards can result in differences in yield and quality that cannot be attributed to differences in climatic conditions between growing seasons. His work focuses on soil variation in vineyards as an essential component of precision viticulture. A primary goal of his team’s work was to determine the smallest number of sampling sites necessary to obtain a realistic large-scale map of soil variability using a single vineyard site in California. The study site showed great parent material variability, which typically requires a larger than expected number of sampling points to allow precise mapping. Additionally, cultivation and grading of the soil prior to planting of the vineyard has masked natural variability in the surface horizon, which should be taken into consideration if only mapping surface soils. Dr. Lambert utilized ratios of vine trunk diameter to silt, CEC, and sodium as informative measures for examining the effects of individual soil components on vine vigor. Future work will include analyses of wine quality throughout the vineyard block in this study.Ana Aizpurua (NEIKER Instituto Vasco de Investigación y Desarrollo Agrario) presented
a progress report from a study that was carried out during 2005 on an 8-ha field located in Oyón (Spain) where Tempranillo (red cultivar) is grown. The aim of her work was to study the variability associated with soil, grape yield and juice quality parameters. Yield was measured and soil samples were taken at various depths. Soil parameters were measured at various depths as in the above UC Davis study and additionally, in 100 out of the 200 initially selected sample points the following juice quality parameters were measured: probable alcohol degree, total acidity, pH, malate, tartrate, K and anthocyanin concentrations. Grape yield showed the largest within-field variability, and soil phosphorus content accounted for the highest variability in soil, and was greater in areas of soil import, while anthocyanin and malate concentrations were the most variable factors regarding quality of juice.
Scott Burns, Portland State University presented his findings from a completely updated study of over 210 Pinot Noir vineyards (5249 acres) in the northern Willamette Valley, Oregon. His talk was more regional in nature than block specific, which may reflect the youth of the Oregon industry in comparison to California or European wine regions. He revealed that two soil series dominate Willamette Valley vineyards, but three other soils have also shown great promise. The two dominant soils are the Jory (1504 acres), an Ultisol (low nutrients soil) developed on 15 million year old basalt bedrock, and the Willakenzie (1245 acres), an Alfisol (high nutrient forest soil) developed on marine sedimentary rocks of the foothills of the Coast Range. Both are very old soils (over 50,000 years old), well-drained, on south-facing slopes, xeric moisture regime (Mediterranean), red, and located between 300' and 800' elevations. The three additional soils of interest are Laurelwood, Yamhill and Cornelius.
Most of the Mid Atlantic is composed of soils from three main orders: low nutrient soils (Ultisols), high nutrient forest soils (Alfisols), young soils (Inceptisols). It is interesting to note that these soil orders are similar to those mentioned as prime grape growing soils in Oregon; however, not all other factors are equal, such as climate and parent material. Interestingly, Dr. Burns also stated that in their study it was observed that poison oak grew well mostly in areas where the highest quality wines were produced. If only the same held true for poison ivy in the eastern US! Perhaps it would be a worthwhile effort to look for such bio-indicators of good grape growing soil here in Virginia?
The use of GPS to record plant and soil information in a GIS database, along with the use of geostatistical tools, has given a new impetus to vineyard classification and terroir studies by providing a means of visualizing complex soil properties and modeling the soil-vine relationship. It is the knowledge gained from detailed soil studies that offers an opportunity to implement different vineyard management strategies to achieve both vineyard balance and wine style objectives. Ongoing work by Cornell University is currently investigating the use of precision viticulture for vigor mapping and nutrient management of Concord vineyards. As the wine industry in Virginia advances I foresee a place for more of these technologies to be implemented on new and existing vineyard sites.
|Virginia vineyard meeting series. Chateau O’Brien, Markham, VA. Topics include cover crops, crop estimation, pruning, post harvest disease management, late season insect scouting and control, WPS review. Aug 9th, 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. Directions From Front Royal: Take I-66 East to exit 18 Markham, turn right on Leeds Manor Rd. VA 688, cross Route 55 and turn left onto Old Markham Road, across from old Post Office, turn right onto Railstop Rd., end at 3238 Rail Stop Road, Markham. For further information, contact Mr. Kenner Love, Rappahannock County Cooperative Extension, (540-675-3619).|
|Advanced Wine Making Workshop. Linden Vineyards. Linden, VA. The finer points of artisan winemaking are covered is this seminar with time spent in the vineyard, cellar, classroom and tasting. Style and quality issues are the focus. Participants should have some winemaking experience or have taken the Winemaking Basics Seminar. Pre-registration required. Limited space. http://www.lindenvineyards.com/|
|Pennsylvania Association of Winegrowers Annual Summer Vineyard Walk Around. At the Fruit Research and Extension in Biglerville, PA. 9 a.m. to 5 p.m. Tour of variety and pathology experiments run by Dr. Jim Travis and his team at FREC and tasting of research wines by extension enologist Stephen Menke. Registration and pre-registration required. Pesticide credits are available. For information, call Mark Chien or Stephen Menke.|
|Virginia Tech, Penn State and University of Maryland viticulturists will offer a one-day “Wine Grape Production Primer” shortcourse at the AHS Jr. AREC in Winchester VA. This has become an annual event and fills quickly. Stay tuned for further details. For those interested in learning the basic aspects of site selection, economics, vineyard establishment and vineyard management, this is a “must.”|
"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
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595 Laurel Grove Road
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