Vineyard and Winery Information Series:
Vol. 22 No. 5, September - October, 2007
Dr. Tony K. Wolf, Viticulture Extension Specialist, AHS Jr. Agricultural Research and Extension Center,
Virginia’s hot, dry years typically result in our best overall vintages and 2007 may well be remembered as one of those benchmark years. Fruit quality reports from around the state have been very positive and the absence, to date, of tropical storms has contributed to clean, concentrated fruit. With an unusually quiet Atlantic at this writing, I’m beginning to think that even the later ripening reds might escape rains from tropical depressions this year.
The extent of crop loss due to the Easter Weekend frost was quite variable but will have some impact on overall yields in 2007. Despite losing most of our primary shoots on many of the varieties in our Southern Piedmont AREC vineyard at Blackstone (low temperature of 18°F on Easter Weekend), we still needed to remove a considerable amount of pre-veraison crop from many of the varieties to avoid overcropping. While the Easter Weekend and ensuing cold spell delayed the start of the season, the heat and dry conditions of summer advanced veraison; harvest commenced from 7 to 14 days ahead of average for many varieties/locations.
Our vineyard visits and volunteered summaries of harvest paint a reasonably favorable picture of harvest grape quality throughout the state, although as in every vintage there were exceptions and disappointments. We had an above-average number of reports of hail damage to vineyards in 2007, including a brush with hail in our Winchester vineyard in late-August. Pest pressure seemed to be average. Growers who experienced outbreaks of downy mildew or powdery mildew should re-evaluate their spray programs and consider the potential that they may be using fungicides to which the pathogen has developed resistance. Japanese beetles were persistent and abundant in some vineyards, but I would categorize the incidence in our Winchester vineyard as below-average. Pierce’s Disease continues to affect some southern Piedmont and southeast Virginia vineyards, but I saw fewer new cases in our Blackstone vineyard in 2007 and I’m encouraged by the observations and comments of Dr. Jim Kamas of Texas A&M University who spoke about the disease at the VA Vineyards Association’s summer technical program in Williamsburg (“… it’s manageable”).
I see two pervasive problems in many of our vineyard visits that will require a sustained effort to remedy and our oldest vineyard in Winchester exemplifies both situations. One is an increasing number of apparently diseased vines where the disease can be virus (e.g., leafroll, corky bark), fungal (e.g., canker diseases, Petri’s Disease), or other (PD, grapevine yellows, crown gall) pathogens. Part of the problem, particularly with older plantings, relates to poor nursery stock and this cause will likely continue to exist until we have a robust clean-stock program nationally available. But even clean vines can be infected in the field by some of our indigenous pathogens and as vineyards age, the incidence of diseased vines often increases. We can slow those infections in some cases, but removal and replanting of affected vines is needed in many cases to regain or elevate the overall quality of a vineyard block. If you question that, taste the difference in berry ripeness of leafroll-affected vines vs. unaffected vines from the same block when the two are cropped at similar levels. In a somewhat analogous fashion, the other chronic problem that we’re seeing, particularly with older vineyards, is nutritional deficiencies. Mardi Longbottom speaks to this in her nutritional review, below. Due in part to the dry weather we saw a number of vineyards that had nitrogen deficiency symptoms. Like some diseases, the nutritional problems are often chronic – the dry season exacerbated symptoms, but many older vineyards are under-fertilized. Attention to soil pH, soil nutrient balance and soil organic matter is needed in many cases. Again, our oldest vineyard block at Winchester is a good example of one such vineyard that requires attention. Use the fall and winter to order vine replacements and to make amends with your vineyard nutrient program.
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As in previous years I’ve included in Table 1 a listing of the spray materials used in our research vineyard at Winchester in 2007. This is not intended as an endorsement of specific products. There are many options for an effective spray schedule, and ours is but one. Our program worked and if you gain some positive benefit for your program next year, then it's worth the time to print it. Some considerations: Spray adjuvants were not generally used in our program and most of the listed products were used at a higher or highest rate when a range of rates was specified on the label. Vines are primarily vinifera (Chardonnay, Cab franc, Cab Sauvignon and Viognier), so an intensive spray program for mildew control is used. We are concerned about mildew resistance to sterol-inhibiting and strobilurin-type fungicides and generally include a modest rate (2 lbs/acre) of sulfur in all sprays, with a heavier rate (5 lbs/acre) if sulfur is the sole fungicide for powdery mildew (e.g., 30 July spray). Rainfall, forecast rain, plant growth stage and systemic or non-systemic nature of material determine our spray frequency.
As with previous years, our disease management program was essentially based on a 10-day (±) program in the pre- to immediate post-bloom period, extended somewhat after the first of July. Climbing cutworms have been more abundant as we have allowed more weed residue in the vineyard in recent years. The addition of Imidan insecticide to the Intrepid insecticide might not be necessary but is aimed at minimizing resistance development and extending the spectrum of control options for climbing cutworms. Intrepid was used again in June for grape berry moth while Assail was used twice for Japanese beetles. Given our concerns for strobilurin resistance, the two Pristine sprays were our only sprays that contained a strobilurin.
Table 1. Fungicides and insecticides, and stage of growth at each application, used in the AHS AREC training system vineyard during 2007.
|Date||Pesticides used||Growth stage|
|12 April||Imidan 70W; Intrepid 2F||bud swell|
|20 April||Imidan 70W; Intrepid 2F||bud burst|
|9 May||Penncozeb 75DF; sulfur||10" shoots|
|19 May||Nova 40W; ProPhyt; sulfur||24” shoots|
|1 June||Pristine; sulfur||bloom|
|12 June||Penncozeb 75DF, Intrepid 2F, Quintec, sulfur||fruit-set|
|22 June||Penncozeb 75DF, Vangard, sulfur, Intrepid 2F, ProPhyt||cluster closing|
|30 June||Pristine; ProPhyt; sulfur; Assail 30 SG||berries hard & green|
|16 July||Quintec; sulfur; Assail 30 SG; ProPhyt||berries hard & green|
|30 July||Sulfur (5#/ac); ProPhyt||beginning veraison|
|10 Aug||Quintec; ProPhyt||veraison|
|24 Aug||ProPhyt, Vangard WG||Post-verasion|
Mancozeb (Penncozeb) forms the backbone of our downy and black rot control program early, with a greater reliance on phosphorous acid (ProPhyt) mid- to late-summer. Sulfur was last applied about 40 days prior to earliest harvest (Chardonnay). Vangard was applied at cluster-closing and again post-veraison for Botrytis.
As with our previous recommendations (http://www.virginiavineyardsassociation.com/presentations.php), we withheld sulfur application in the 6 weeks prior to harvest to minimize hydrogen sulfide development in wines. Results: Vines were free of mildews and black rot. Some botrytis and non-specific bunch rots (less than 10%) occurred in Chardonnay and Traminette; however, some of the non-specific rots appeared to result from hail injury in late-August.
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Grapevine petiole analysis is generally performed at full bloom (80% flowers open) to gain an overall representation of vine nutrient status. Petioles (leaf stems) are collected from opposite bunches and sent to a diagnostic laboratory for analysis. Performing annual petiole analysis is a useful tool to monitor vine nutritional status from year to year and to assess the impacts of soil or foliar remediation made early in the season or in the previous season. This year there were some notable results that were common to many growers across the state.
Nitrogen: Many vineyards reported slow growth and yellowing of the older leaves, symptoms typical of nitrogen (N) deficiency. Petiole analyses confirmed low nitrogen values. Low nitrogen levels measured in the petioles can be caused by dilution brought about by vigorous growth, or, they may reflect low soil moisture status which prevents uptake from the soil by the roots. This year the latter was more likely to be the cause.
The general recommendation for growers who returned low nitrogen results was to apply 20-30 lbs/acre of actual N to the undervine strip. Most regions received some rain at around veraison which mobilized soil nutrients and vine appearance improved over the following weeks. Blocks that had low nitrogen this year should also receive a post-harvest soil application of 20 lbs/acre of actual nitrogen.
Next year consider a split application of 50 lb/acre of actual nitrogen applied undervine. To maximize root uptake, fifty percent (25 lb/ac) of the total nitrogen should be applied at budburst and the balance (25 lb/ac) applied at flowering, keeping in mind that the fertilizer must be incorporated into the soil soon after spreading with either rain or irrigation.
Soil nitrogen stores are drawn upon each year during the annual cycle of fruit and vegetative production. To replenish the nitrogen removed from the soil an annual maintenance application of 50-75 lb/ac actual N per year is recommended.
Potassium and magnesium: Many growers had elevated petiolar potassium (K) coupled with low magnesium (Mg) levels. This is not uncommon for vineyards in Virginia. Short-term Mg deficiencies can be treated with foliar application of Epsom salts, however, long-term results can be better achieved by the application of dolomitic lime or other magnesium fertilizer to the soil.
Boron: Marginal levels of boron were measured in a few vineyards. Boron (B) uptake may also have been prevented by low soil moisture and an inability of the vines to extract it from the soil.
Boron deficiency is commonly associated with poor fruitset. If bunches on varieties that have low B values are loose with fewer berries per bunch than normal it is likely that low boron status has affected reproductive development. If this is the case the born deficiency can be corrected early next season to prevent any negative effects on yield next year. Petiole analysis should also be repeated on these vines next year at flowering.
Other nutrients: Many results can be confounded by contamination by fungicides. High levels of sulphur, phosphorus and manganese are commonly caused by contamination. Conversely, Mancozeb applied as part of your fungicide program will assist to increase vine manganese status.
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14-15 November 2007
What: Southwest Virginia Wine Grape Grower’s Conference
When: Wednesday, 14 November – Thursday, 15 November. Starts at 8:30 am on 14 November and ends 4:00 pm on 15 November
Where: Quality Inn – Roanoke Airport, Roanoke, Virginia
Registration: Contact Jon Vest, Virginia Cooperative Extension, Roanoke for registration information (email@example.com). Registration materials will be mailed separately with full program agenda.
This will be a team-taught conference aimed at prospective growers and those with several years’ experience who are looking to improve vineyard management practices. Day one of the conference targets those who are exploring wine grape growing opportunities in the region, with an emphasis on the Southwest Virginia environment. Topics will include economics, site selection, varieties, and vineyard establishment, including materials and methods. More advanced aspects of established vineyard management (canopy management, pest management, pruning and training, cold injury avoidance, etc.) will be discussed the morning of day two. Classroom principles will be reinforced with a hands-on review in a local vineyard on the afternoon of the second day.
Information: Tony Wolf, 540-869-2560 x18 (firstname.lastname@example.org) or Jon Vest, 540-772-7524
16 November 2007
What: New growers workshop
When: Friday, 16 November. Starts at 8:00 am and concludes at 5:00 pm
Where: Biglerville, Pennsylvania
Registration: Contact Mark Chien of Penn State Cooperative Extension (email@example.com) for program information and registration materials.
An intensive, one-day workshop for new wine grape growers in the mid-Atlantic region. Program will be similar in content to that described for the Roanoke meeting (see above). Pennsylvania program is also team-taught with contributions from Penn State, Virginia Tech, and Texas A&M University.
7 - 9 February 2008
What: Virginia Vineyards Association annual technical conference
When: February 7 - 9, 2008
Where: Omni Hotel, Charlottesville VA
Hold the date. Program details are currently being organized. Program will include a half-day program on Petit Verdot and two days of technical presentations to include:
Information will be available at:: http://www.virginiavineyardsassociation.com/
Seminars at Surry Community College, Dobson, NC
Grape and wine seminars are being offered at Surry Community College in Dobson, NC. Interested persons can obtain registration information by calling 336-386-3244 at least one week in advance of the seminar. Seminar titles, dates and registration costs are:
- Berry sensory lab; 6 October ($75)
- Premium/Profitable Wine Production from Hybrid Varieties; 8 December ($50)
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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: firstname.lastname@example.org
Commercial products are named in this publication for informational purposes only. Virginia Cooperative Extension, Virginia Tech, and Virginia State University do not endorse these products and do not intend discrimination against other products that also may be suitable.
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