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 Knowledge for the CommonWealth

Viticulture Notes

Volume 13, Number 1 -- January-February 1998

Dr. Tony K. Wolf, Viticulture Extension Specialist

Table of Contents

I. Current situation

II. Abound® fungicide

III. Upcoming events

I. Current Situation:

A. How hardy are the grapevines?: It's a perennial question and one that has been intensified this year given the warmer than average December and January. The daily high and low for the Agricultural Research and Extension Center vineyard at Winchester are shown for December and January in Fig. 1. With very minor modifications, those temperatures are going to be close to the registered temperatures in many of the major grape producing regions of the piedmont and Shenandoah Valley. Our extreme low (to date) occurred on 1 January with a low of 11°F. One week later we recorded a high of 67°F. That's what climatologists call "continentality", but itıs not the greatest or swiftest swing that weıve seen.

Figure 1 (at left). Daily high and low (°F) air temperatures at research vineyard of AHS Agricultural Research and Extension Center from 1 December 1997 ­ 30 January 1998.

While the relatively warm weather has raised concern about deacclimation of grape buds, and potential for cold injury, the reality of vine hardiness is more upbeat. Table 1 provides a relative comparison of bud cold hardiness of selected varieties during the 1996-1997 and 1997-1998 winters ­ with a focus on the period from December through January. By way of review (see Viticulture Notes, Vol. 12, No. 1), temperatures in December of 1997 dipped to single digit figures just before Christmas, then rose into the seventies (Winchester) around the first of January. Lows of zero to around ­6.0°F were recorded in late January. Most varieties are currently less cold hardy than at a comparable period of 1997. Nevertheless, it would currently take temperatures around 0°F or colder to cause significant bud kill with most of the varieties shown in Table 1. One exception is Cabernet Sauvignon, clone 8, which had a mean LTE for buds of +1.6°F when assessed on 29 January. We've been consistently impressed with the relative cold hardiness of Petit Verdot, which currently has a 7-degree advantage over Cabernet Sauvignon. The apparent cold hardiness of Viognier (-8.5°F), as measured on 30 January, reflects a high proportion of secondary buds, due to primary bud necrosis. The data in Table 1 provide a relative measure of varietal cold hardiness, and should not be interpreted as the absolute hardiness if the vines were grown under your conditions at a different time. Furthermore, the data are specific for dormant buds. Dormant buds provide a good index of overall vine cold hardiness in mid-winter, but may overestimate cold hardiness of canes and trunks early in the season or during periods of very warm weather of winter.

Table 1. Mean low temperature exotherm (LTE) temperature of selected varieties at the Winchester Agricultural Research and Extension Center vineyard in January 1997 compared to January of 1998. Mean LTE is an approximation of the temperature that would kill 50% of the buds under field conditions.

Variety Mean LTE 6-10 Jan. 1997* Mean LTE January 1998**
Cab. Sauvignon #8 -2.7 +1.6
Chardonnay #4 -3.1 -2.7
Malvasia bianca -9.4 -3.8
Muscat Ottonel -6.3 -4.7
Petit Manseng -6.0 -1.1
Petit Verdot -4.4 -5.4
Sangiovese -4.0 -0.9
Seyval -8.3 -4.9
Concord . -3.5
Viognier . -8.5

* Data collected between 6 and 10 January 1997.
** Data collected between 23 and 30 January 1998.

B. 1998 Pest Management Guides Available: Virginia Tech's 1998 Pest Management Guides are now available. Virginia-specific recommendations for dealing with insects, diseases, and weeds in grapes are included in the "Horticultural and Forest Crops" volume (publication #456-017). The Guides are annually updated and I would encourage you to regularly update your edition in order to keep abreast of changes in pesticide registration and other rules and regulations that affect pesticide users.

C. Symposium Proceedings available: Proceedings of the IVth International Cool Climate Viticulture and Enology Symposium are available for those who wish to obtain a hard copy. The Symposium was held in Rochester, NY in July 1996 (Viticulture Notes, Vol. 11, No. 3) and featured more than 160 speakers from 20 countries (and 5000 bottles of wine). The proceedings are over 650 pages, and are probably the most comprehensive, contemporary assemblage of viticultural and enological research work in the world. As with the Symposium program, the proceedings are divided into 9 sub-sections, including: Adaptation to regional environments; Vine stress physiology; Ecologically sound winegrape production methods; Vineyard mechanization; Flavor development in the vineyard; Flavor development during fermentation; Wine sensory attributes; Grape and wine genetics; Economics and marketing. Donıt let the Symposium name mislead you ­ most of the information contained in the Proceedings has either direct or indirect application in Virginia and other "warm" climate viticultural regions. I would encourage serious grape growers and vintners to obtain a copy of the Proceedings and spend some long winter evenings studying the wealth of information contained. The Proceedings are available for $85 (payable "ASEV/ES") from: Department of Food Science and Technology, Cornell University/NYSAES, Geneva, NY 14456, Attention: Ms. Nancy Long.

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II. Abound® the first representative of a new group of grape fungicides:

Contributed by Dr. Anton Baudoin, Associate Professor, Plant Pathology, Virginia Tech

Abound®’ (common name: azoxystrobin) is a new fungicide from Zeneca Ag Products that was registered for use on grapes in 1997. Availability was limited, so many growers have probably not yet had a chance to use it. Abound® is the first of a new chemical "family". Additional members of this group (strobilurins) may well become available in the near future since other companies have developed compounds with similar activity, and one of them (Sovran from BASF) could conceivably become registered by 1999.

The way the activity of strobilurins was discovered is interesting. Historically, most fungicide groups have been discovered by testing massive numbers of synthetic chemicals against the target pathogens. However, strobilurins are based on the antifungal activity of a natural compound produced by a small mushroom, apparently to keep competing fungi at bay. The chemistry of this compound had to be modified until acceptable stability in sunlight along with other properties needed for an agricultural fungicide were achieved, so the resulting fungicides are not natural. Nevertheless, toxicological tests with Abound® were sufficiently favorable that EPA approval of Abound® was obtained using the fast track for reduced-risk pesticides. In addition to grapes, registrations for this fungicide now include peaches, tomatoes, turf, and peanuts (trade names Heritage and Quadris)

Strobilurins have a broad spectrum of activity against grape diseases; Abound® has given excellent results against black rot, both powdery and downy mildew, and Phomopsis cane and leaf spot, when applied on a 10-14 day schedule. Of the major fungal disease targets of grape, only Botrytis is apparently little affected. Abound® can be applied up to 14 days before harvest and, according to a Zeneca representative, has not shown any evidence of interfering with the yeasts used in wine making. Thus, Abound® is worth considering for downy mildew control and may be used during much of the 66 days before harvest when mancozeb and Ridomil cannot be applied.

Abound® should be used primarily as a preventative fungicide, even though the chemical does penetrate slowly into plant tissues. In May 1996, I applied Abound® in the field the day after a black rot infection period, and got good control while mancozeb applied at the same time allowed considerable infection. (Thanks to Stephen Haskill for making several rows of vines available for testing in both 1996 and 1997.) In preliminary greenhouse tests, I have also found some after- infection activity against black rot, but significantly less than for Bayleton and Nova, which remain the materials of choice for after-infection use.

The recommended spray interval for Abound® in a preventative schedule is 10-14 days and the materialıs costs is approximately $20-30 per application per acre, so itıs not cheap. This is balanced by the fact that it may take two fungicides (for example, Nova or Bayleton plus captan or mancozeb) to obtain a comparably broad spectrum of activity and a similar level of disease control. Under severe black rot pressure in 1996 (unsprayed vines had 96% berry loss), a program of Abound® (3 sprays) alternated with mancozeb on a 14-day schedule kept losses at 3-5% berry loss, while a program of mancozeb alone every 14 days allowed 26% loss. In a 1997 comparison of Abound® with Bayleton, both applied every 14 days, black rot control was excellent and essentially equivalent for both.

The cost will probably deter many people from starting an Abound®-only spray program, but there is another very important reason to rotate with other chemicals, and that is prevention of resistance development. Resistance development by fungi is a concern because the action of strobilurins is very specific (one process in the fungal cell affected). Preliminary data developed by Zenecaıs scientists suggest that several changes in the target site are needed to destroy sensitivity, raising the hope that resistance will not occur all that easily. However, this conclusion remains tentative until several additional years of field experience are available. Rotation of Abound® with other fungicides is mandated by the label as a resistance management strategy (no more than 2 consecutive applications; no more than 6 applications per season).

On the subject of resistance management, the availability of Abound® provides a valuable tool to reduce the risk of developing powdery mildew resistance against ergosterol biosynthesis inhibitors (EBI's: Bayleton, Nova, Rubigan, Procure). Overly frequent use of these fungicides has resulted in EBI-resistant powdery mildew strains appearing in a number of areas, both in grapes and other crops, and rotating with Abound® can prevent over-use of EBIıs.

As with any new compound, even though they are extensively tested in a wide range of field situations, there is still room for surprises. It was recently discovered that ® is very phytotoxic to Macintosh apples (and cultivars with Macintosh among their parents). The 1998 label will state that possible drift to apples should be scrupulously avoided, and that a sprayer that has been used to apply Abound® should not be used to apply any chemicals to apple. With new materials, one should always be on guard for such unexpected situations.

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III. Upcoming events:

A. Annual grape pest management and research topics update

Where: Omni Hotel, Charlottesville, VA

When: Monday, 20 April 1998; 8:00 am - 5:00 pm.

Registration: $30 per person if registering before 10 April. Registration increases to $40 for registrations received after 10 April or at door. Registration includes morning coffee and buffet lunch.

Directions: The Omni Hotel (804-971-5500) is located at 235 West Main Street in downtown Charlottesville, Virginia. Perhaps the easiest means of entry is via Route 250 by-pass on the east side of Charlottesville. From Rt 250, take McIntire Rd approximately one mile to junction of High St. Continue across High St. and enter Hotel parking on left (check next newsletter on status of parking fee).

Private Pesticide Applicators Recertification Credit: This course has been approved for full credit towards Private Pesticide Applicators, Category 80, Agricultural Pest Control certification. To obtain this credit, you must arrive and register before the start of the program, and you must sign out at the end of the program. Be certain to bring your current VDACS Pesticide Applicator Certificicate number with you.

Pest Management Program (20 April 1998):

8:00am On-site registration (coffee available) (allow 10 to 15 minutes to register!!)
8:30 am Powdery mildew problems of 1997, suggestions for 1998 (discussion will illustrate several powdery mildew problems observed in 1997 and how growers can prepare for 1998).
Dr. Tony Wolf, Virginia Tech
9:15 am Spray application technologies (to address questions on sprayer performance, gallonage per acre, alternate row spraying, and canopy volume compensation as these variables affect spray material coverage and pesticide efficacy)
Dr. James Travis, Pennsylvania State University
10:15 am Vineyard pesticide usage survey and implications of the Food Quality Protection Act
Dr. Mike Weaver, VA Tech
10:45 am Abound®’ fungicide (cost, integration, and recommendations for using this fungicide)
Dr. Anton Baudoin, VA Tech
11:15 am European red mite management (research update)
Dr. Doug Pfeiffer, VA Tech
12:00 pm Buffet lunch in Omni
1:30 pm Trouble-shooting electric deer fence failures (design principles, selecting appropriate energizers, observations on common field problems)
Mr. Lewis Sapp, Gallagher Power Fence, Inc.
2:30 pm Black rot and downy mildew control strategies and options for disease forecasting (this talk will cover the basics of these two diseases including control options. Integrated with the topic will be a discussion of current research on disease forecasting, including pros and cons of several options that growers currently have available).
Dr. James Travis, Pennsylvania State University
3:30 pm Safe handling of pesticides (Discussion will demonstrate safe handling of pesticides, including appropriate use and care of Personal Protective Equipment (PPE), common modes of pesticide contamination, and pesticide spill control)
Mr. Charlie Goodman, Virginia Cooperative Extension
4:15 pm Common problems observed with compliance of State and Federal Pesticide laws
Mr. Bob Buckwalter, VDACS, Office of Pesticide Services
4:45 pm Completion of exit forms and adjourn (Must be completed to receive full recertification)

Program is subject to slight revision in time or composition.

B. Pruning demonstration:

When: 1:00 pm on Friday, 27 February 1998

Where: VA Tech, AHS Agricultural Research and Extension Center (540-869-2560).

Details: Principles and practices of dormant pruning; current vineyard situation; pruning demonstrations of established vines trained to bi-lateral cordons with VSP, open-lyre, and Geneva Double Curtain.

Directions: The AHS AREC is located approximately 7 miles southwest of Winchester, VA. From Interstate-81, take the Stephens City exit on the south side of Winchester. Go west into Stephens City (200 yards off of I-81) and proceed straight through traffic light onto Rt 631. Continue west on Rt 631 approximately 3.5 miles. Turn right (north) onto Rt 628 at "T". Go 1.5 miles north on Rt 628 and turn left (west) onto Rt 629. Go 0.8 miles to AREC on left.

C. Regional "beginners" seminar:

When: 2:00 pm on Tuesday, 10 March 1998

Where: Dyeıs vineyard and winery, Russell County, VA (540-873-4659)

Details: This is an abbreviated version of our full-day beginners grape growing seminar, and will be aimed primarily at interested growers in the southwest region of Virginia. Topics will include site selection, economics, varietal choices for the southwest of Virginia, and basics of vineyard establishment. There will be minimal coverage of vineyard operations. Please note that a full-day beginners seminar is tentatively planned in early May at Winchester. Registration: Free. However, due to limited seating, you are encouraged to contact Mr. Paul Chambers, Russell County Cooperative Extension Service (540-889-8056), to be assured of seating.

Directions: Dye's Vineyard (540-873-4659) is in Russell County, in the southwest region of Virginia. From interstate 19, go west on US Rt 80. Turn left at state route 620 and go one-half mile.

D. Regional meetings and seminars:

When: March 7, 1998
What: Finger Lakes Grape Program
Where: Waterloo, NY
Program details: Pest management research and recommendations update, varietal recommendations, nutrition and grape marketing are featured topics Registration and other information: Contact Finger Lakes Grape Program, at 315-536-5134.

When: March 14, 1998
What: New Jersey Grape Expectations
Where: Forsgate Country Club, Jamesburg, NJ
Program details: ³This day-long symposium is designed for professionals, amateurs and other interested in grape growing or winemaking Registration and other information: Contact Dr. Joseph Fiola, Rutgers University at 609-758- 7311.

When: March 15-18, 1998
What: Wineries Unlimited: 1998
Where: Lancaster, PA
Program details: Mix of viticulture, enology, marketing and trade show fare. Vit./enol. sessions on Pinot noir, ice wines and late-harvest wines. Novice or beginner through experienced operators. Registration information: Call 800-535-5670. Other information at: //

When: July 22-24, 1998
What: American Society for Enology and Viticulture/Eastern Section Annual Meeting
Where: Crown Plaza Hotel, Grand Rapids, Michigan
Program details: Viticulture and enology research reports, international symposium on sparkling wines, trade show and social activities highlight this educational and fun annual meeting. Registration information: Contact: Dr. Charles Edson, Secretary ASEV/ES, (517-353-5134)

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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'd like to receive "Viticulture Notes" as well as Dr. Bruce Zoecklein's "Vintner's Corner" by mail, contact Dr. Wolf at:

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

or e-mail:

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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