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Virginia Cooperative Extension -
 Knowledge for the CommonWealth

Viticulture Notes

Vineyard and Winery Information Series:
Vol. 19 No. 3, May-June 2004

Dr. Tony K. Wolf, Viticulture Extension Specialist

Table of Contents

  1. Reminders - disease issues, spreader/stickers, resistance management canopy management tips, plant tissue analysis
  2. Wanted: vineyard with European red mite infestation
  3. Upcoming meetings


Disease issues:

Powdery mildew:

Downy mildew:

Black rot:


Question about the use of spreader-stickers:
Questions about the efficacy of spreader/stickers recur annually. Dr. Wayne Wilcox, Cornell University, provides the following, slightly edited question and answer discussion on this topic:

Question: "Given the rain that inevitably falls right after a spray, isn't it a good idea to use Nu-Film 17, Cohere, or one of the other adjuvants?"

Reply (Wilcox): This is probably the most frequently-asked question that I get, and the one for which I have no single good answer. In classic university-speak, "It all depends". Many products (e.g., most of the mancozeb and captan products) are already formulated with surfactants. A few (Rovral comes to mind) have been shown to benefit from the addition of surfactants. For others, experimental data shows no benefit or there is simply little experimental data to draw upon. Adjuvants are not the same. People always think they're getting a "spreader-sticker" when they add an adjuvant, but Rovral, Phostrol, and the SI fungicides need to be *absorbed* in order to work, so you don't want them to stick (e.g., the benefit for adding a surfactant with Rovral has been to increase absorption). In contrast, you want mancozeb, captan, and sulfur to stick, whereas adjuvants that promote absorption may also promote phytotoxicity. For example, when Flint first came out, I know that the company was discouraging the use of organosilicate adjuvants (e.g., Kinetic) for this very reason.

My approach has been to tell growers some version of the above, and suggest that if the label recommends use of a surfactant, it's a good idea. But given the uncertainties, if it makes somebody feel better to include the surfactant, I won't try to talk them out of it. And as a consultant, I'd be doubly hesitant to talk somebody out of it, because any ensuing problem would be ascribed to that very recommendation, regardless of the real reason.

Like I said, no single good answer. I can't, in good conscience, aggressively push the general use of surfactants or other spray adjuvants. I think that they're probably a waste of money much of the time, but I don't feel confident in defining such times. So, the easy answer is, if local experience shows no problem with a particular surfactant/product combination, you "might" help yourself, and the additional cost is relatively marginal.

Resistance management (this is an annual reminder)
The development of powdery mildew, downy mildew, or botrytis strains that are resistant to some of our newer fungicides is a reality. Once resistant strains appear, the fungicides will exhibit reduced efficacy, or no efficacy. To slow the development of resistant fungal strains, adhere to the following recommendations:

Spray program at the research vineyard at Winchester:
We've made four fungicide applications to-date at the research vineyard at Winchester (Table 1). As with past presentations of our spray schedule, this is not intended to recommend one product over another, or to say that the same program should be used in your vineyard. We do not have a specific, pre-planned "schedule" that we follow for spraying. We consider the growth stage of vines, the environmental conditions since the last spray, the products previously used, the products that can currently be used, resistance management (note the use of three applications of sulfur thus far in 2004 in Table 1), and our need to do canopy management in the vineyard.

Table 1. Fungicides and insecticides, and stage of growth at each application, used in the AHS AREC research vineyard in April-May 2004. "Precip." is the amount of rainfall that was recorded since the last spray (e.g., 0.43 inches of rain was measured between 6 and 13 May).

Date Pesticides used Growth stage Precip.
27 April Penncozeb 75DF, Nova 40W, Microthiol Disperss (sulfur) 3 -5" shoots  
7-May Penncozeb 75DF, Microthiol Disperss (sulfur) 6 - 8" shoots 0.43
17-May Pro-phyt, Elite 45DF, Microthiol Disperss (sulfur) 16-36" shoots 1.30
21-May Ridomil Gold MZ, Elite 45DF, Microthiol Disperss (sulfur) pre-bloom 0.51

Let me remind you of the comprehensive discussion, "Grape Disease Control, 2004", that Dr. Wayne Wilcox provided (and which I sent out on my listserv) in April. It's well worth picking that document back up and re-reading it now. I refer back to my own copy on a regular basis as I think about the fungicide options and how to structure a spray schedule.

Winter-injured vines: No or very little crop, just leavesŠ do you abandon your spray program? Absolutely not. You can lighten up on the black rot and berry moth sprays, but keep the foliage free of powdery and downy mildew, at least through September. It's important that these vines be given a good opportunity in 2004 to develop reserve carbohydrates for the 2005 season. They won't do that if mildew destroys the canopy by mid-summer.

Canopy management tips:

Plant tissue analysis reminder:
Full bloom is the recommended time for doing routine plant tissue analysis for nutrient status determinations. Plant tissue analysis is part of a comprehensive vine nutrition management program, to be used in conjunction with soil testing and visual examination of vines. Please see the May-June 2002 Viticulture Notes for a more in-depth discussion of the whys, hows, and what-if questions that go along with plant tissue analysis.

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II. Wanted: Vineyard with European red mite infestation:

I (TKW) was asked by Crompton Uniroyal Chemical to evaluate Acramite 50WS miticide under a commercial situation during the 2004 growing season. We conducted a similar evaluation of Acramite in 2002 for European red mite (ERM) control and, we are seeking a similar situation in 2004. Acramite is labeled for use on grapes, and we would not need to destroy or otherwise harvest crops. We would need:

If you are interested in helping out by providing an affected vineyard for our research, please contact me at or call 540-869-2560 x18. Thanks in advance for your consideration.

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III. Upcoming meetings:


12 Maryland Grape Growers Association Summer Field Day. Golden Run Vineyard, Hans and Jennie Schmidt (east of Chesapeake Bay, Sudlersville, MD). Tony Wolf is the invited speaker ("vineyard design and management: lessons learned and mistakes worth avoiding"). See for detailed program and directions. Info. 410-438-3679 (Schmidt's).

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

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.


13-16 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. Full program description and registration information is available at:

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. Directions: From Orange, south on Rt. 15 Business, turn left on Rt. 647 (Old Gordonsville Rd.), cross RR track, go 100 feet and turn left on Berry Hill Lane.

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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

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