Viticulture Notes

Vineyard and Winery Information Series:
Vol. 22 No. 6, November - December, 2007

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

Table of Contents

1. Question from the field and news notes
2. Blackstone vineyard progress report
3. Upcoming meetings (compiled by Mark Chien, Penn State)

I. Question from the field:

Q. We’ve started dormant pruning our vineyard and I’m seeing the need to replace trunks and cordons on some vines.  I have good replacement canes in place but my question relates to concerns about wood-rotting fungi, and specifically whether I need to use a wound-dressing or other treatment on the severed trunks or cordons?

A. Fungicidal wound treatments have been used in the past to help minimize the likelihood of pruning wounds being infected by the Eutypa dieback fungus (Eutypa lata) or certain other canker-forming fungi, such as Botryosphaeria spp. This topic was addressed in the November-December 2003 Viticulture Notes (http://www.ext.vt.edu/cgi-bin/WebObjects/Docs.woa/wa/getnews?cat=tt-news-viti&issue=200311). Treatments have included broad-spectrum fungicides, borax, and even detergents.  Treatments that are intended to be used as a wound dressing fungicide require EPA labeling and state-specific approval for such use. In recent years, Topsin-M WSB (thiophanate-methyl) fungicide has been used as a topical treatment of grapevine pruning wounds. A request has been made by Cerexagri-Nisso, LLC to the Virginia Department of Agriculture and Consumer Service’s Office of Pesticide Services seeking a special local needs 24(C) registration for Topsin M WSB fungicide for grapevine pruning wound protection. Such registrations have been granted in other eastern US states in previous years, so I’m optimistic that the registration will be approved in Virginia. As of late-December, I had not found the registration at the VDACS web-site (http://www.vdacs.virginia.gov/pesticides/section24.shtml). I will issue a newsnote via the Viticulture Notes listserv when I learn the registration status.  In the meantime, there are some longstanding, practical guidelines that you can follow to reduce the potential of spreading wood-rotting fungal pathogens. Both Eutypa lata and Botryosphaeria spp. are slow-growing pathogens and it takes some years to cause loss of a cordon or trunk. But left unchecked, the pathogens will cause vascular destruction and loss of vine productivity. Double-pruning is one technique that can be used to manage canker diseases. In double-pruning, an initial pruning cut is made “long” – 5 inches or more beyond the desired point of the cut – during winter pruning.

The resulting “stub” is flagged and removed with a second cut after bud break. Double-pruning is based on the premise that the initial pruning wound might well be infected during winter rains. Because the decay fungi are slow-growing, the second pruning cut would excise the affected cut, and the new wound would be less likely to be re-infected if the vine is in an active state of growth. I should add that the strategy of double-pruning has traditionally been aimed at reducing the incidence of Eutypa dieback. It is unclear whether it aids in reducing the incidence of Botryosphaeria canker under our growing conditions. Removing affected wood from the vineyard and burning or burying it is also recommended as a general strategy for reducing the spread of wood-rotting pathogens

General guidance on dormant grapevine pruning can be found at my website (http://faculty.vaes.vt.edu/vitis).  Go to Dormant Grapevine Pruning and scroll down to view the list of Breeze presentations put together last year by Fritz Westover. Fact sheets for both Botryosphaeria canker and Eutypa dieback (A. Myers) can also be found at my website.

Mardi Longbottom: I regret to pass on the news that Dr. Mardi Longbottom, hired earlier this year as viticulture research/extension associate here at Winchester, has resigned and returned to Australia. We hope to re-advertise the position and begin recruitment for a viticulture research/extension associate soon after the first of the year.

Virginia Vineyards Association’s 2008 Technical Meeting, 7-9 February 2008:  The Virginia Vineyards Association will mark their 25th anniversary at the Association’s annual meeting to be held at the Omni Hotel in Charlottesville, Virginia, 7-9 February, 2008. The program (see VVA website: http://www.virginiavineyardsassociation.com/) includes the following topics:

• half-day program on Petit Verdot
• grape root borer, Pierce’s Disease, and grape berry moth research updates
• review of Eutypa, Botryosphaeria, esca and other wood-decaying diseases
• Viognier wine sensory evaluation
• Training system research
• Use of “electronic nose” in the vineyard and winery
• Half-day program on irrigation
• Banquet, trade show, and much more

Program details are still being finalized but a preliminary program is available on the VVA website. Registration and hotel lodging information will follow in a separate mailing.

“Winter Injury to Grapevines and Methods of Protection”: This is the title of a recently published book from the Extension service of Michigan State University. Written by a team that included Tom Zabadal (Michigan State University) who led the project, Tim Martinson and Martin Goffinet (Cornell University), Mark Chien (Penn State University), and Imed Dami (Ohio State University), the book is the best single-source reference for this important aspect of viticulture. The book is 106 pages and is very well illustrated with many excellent, color photographs and additional figures and tables. In addition to summarizing over 100 years of research and knowledge about the problem of winter injury, the authors added sidebars from growers who shared their experience in dealing with cold injury and methods of protection.
Winter Injury to Grapevines and Methods of Protection can be ordered online from Michigan State University Extension at: http://www.emdc.msue.msu.edu/viewitem.cfm?INVKEY=E2930. The cost is only $15.00.

Nova fungicide news:  I recently received the following note from Brian Olson of Dow AgroSciences, “....Dow AgroSciences will discontinue marketing Nova 40WP fungicide and replace it with Rally 40WSP.  It's the exact same formulation, and has the same EPA registration number, just a different name.  Dow AgroSciences is consolidating labels and product.  Rather than having two products, Nova 40WP and Rally 40WSP, we will have only one, Rally 40WSP.”  This should not affect your ability to use Nova on-hand from previous years.

Table of Contents

II. Blackstone vineyard progress report: 

The 2007 harvest of our variety evaluation planting at Blackstone was relatively trouble-free and the fruit integrity and primary fruit chemistry were above average. The lack of appreciable rainfall, coupled with the use of our on-site irrigation system, resulted in a harvest of rot-free, high quality fruit. Primary fruit chemistry obtained from 50-berry (per replicate) samples collected at harvest is presented in table 1.  With freedom from bird depredation, bees and fruit rot, we allowed fruit to ripen to levels that we have not generally attained in the past at Blackstone. Coupled with the good weather, we had rigorously crop-thinned vines in July to achieve on average about 1.0 to 1.5 pounds of fruit per foot of canopy. With the exception of the very early Muscat blanc, harvest occurred entirely within the month of September, with early varieties (e.g., NY73..[‘Noiret’]) harvested 6 September and the latest-maturing harvested 20 days later. Soluble solids concentrations were often above 22.0 Brix and pH was elevated for a number of varieties (Table 1), although we often see relatively high juice pH at our Blackstone vineyard. Varieties that stood out as superior in fruit chemistry and fruit flavors at harvest were Cabernet Sauvignon, Petit Manseng, Tannat, Norton, Rousanne and Vidal blanc. Wines are being made in the Department of Food Science and Technology at Virginia Tech, and those wines will be shared with industry members through round-table extension meetings.

Despite the damaging Easter Weekend freeze, when the vineyard dropped to 18°F, crop yield per vine was close to target (3.5 to 4.5 tons/acre equivalent) with many of the varieties (Table 2). Data on extent of shoot destruction due to the frost were collected and are presented in Table 3. Varieties that yielded full crops, due to late bud break and/or more fruitful secondary shoots include Cab Sauvignon, Mourvedre, Norton, Petit Verdot, Rousanne, and Vidal.

Training was modified in 2007. We converted vines from the Smart-Dyson training (divided canopy) to vertical shoot-positioned. This was done to facilitate application and removal of bird netting and also to restrict yields. While the dry weather was probably the primary factor in determining fruit chemistry at harvest, the lower yields may also contributed to the riper fruit in 2007 than what we have attained in previous years. In particular, Tannat, Mourvedre, Traminette and Vidal must be aggressively fruit-thinned (and/or dormant pruned) in order to avoid overcropping.

Soil-applied insecticide (Admire-Pro) was applied to 3 of the 6 replicates of each variety in June 2007 (two applications). The insecticide is systemic and may offer some reduction in the leafhopper transmission of the Pierce’s Disease bacterium. The overall incidence of PD was lower in 2007 than in 2006; however, the Admire-Pro insecticide did not appear to have a bearing on PD incidence – at least not in 2007. This treatment will be repeated during the 2008 season with an earlier initial application planned.

Future:  We have three complete harvests from the Blackstone vineyard at this point (2005-2007). Our experience to-date includes the following, preliminary findings:

• • Disease pressure has been greater in this environment than our experience at Winchester. Chardonnay, for example, is very difficult to keep free of powdery mildew.
  • Aleatico and Tempranillo have performed poorly, but for different reasons. Aleatico ripens unevenly and is highly susceptible to bee and green June bug injury, perhaps owing to its aroma. Many of the Tempranillo vines were lost to crown gall or other causes within the first several years of planting (2001). While this might have been due to poor nursery stock, the fruit of apparently healthy vines was highly susceptible to rot. For these reasons, we have removed Aleatico and Tempranillo and those spaces will be planted in 2008 with Merlot and another Cabernet Sauvignon clone. The recently named variety, Noiret (NY73.0136.17) has also performed poorly from the standpoint of primary fruit chemistry. At full ripeness (about 19°Brix) the fruit lack flavor.
  • Varieties that have performed well from a viticultural standpoint include Petit Manseng, Norton, Cabernet Sauvignon, Rousanne and Viognier. Others may perform well if we continue to manage crops, including Petit Verdot, Tannat, Traminette, and Mourvedre.
  • With the exception of Norton, all varieties have expressed some incidence of Pierce’s Disease (PD) and this will continue to be a threat in the southern Piedmont as winter temperatures remain above long-term, historical average.
  • Muscat blanc has shown very poor fruitfulness (lack of cluster development) in two recent seasons.
  • Wines have not been formally evaluated from this effort yet.

Table 1.  Harvest date and primary fruit chemistry of varieties/clones being evaluated at the Southern Piedmont Agricultural Research and Extension Center, Blackstone, Virginia, in 2007.

Table 2.  Components of crop yield for varieties/clones being evaluated at the Southern Piedmont Agricultural Research and Extension Center, Blackstone, Virginia, 2007.

Table 3.  Extent of bud break on 13 April 2007, percent frost damage, and resulting crop data from vines grown at the Southern Piedmont Agricultural Research and Extension Center, Blackstone, Virginia, 2007.  Varieties that are shown in bold text sustained relatively minor frost injury by virtue of their later bud break. Others, such as Cabernet franc clone #1 yielded our target crop level (about 4.0 tons/acre equivalent) despite loss of nearly one-half of primary shoots.

Table of Contents

III. Calendar of Regional Viticulture and Enology Events for 2008. 

Appreciation and credit for this calendar is given to Mark Chien, Wine Grape Educator with Penn State University. Mark has gone the extra mile this year to compile a comprehensive listing of meetings and workshops from around the East and Mid-West.  Thank you, Mark.

Table of Contents

"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

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.

Visit Virginia Cooperative Extension.

Visit Alson H. Smith, Jr., Agricultural Research and Extension Center.