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Viticulture Notes

Vineyard and Winery Information Series:
Vol. 23 No. 1, March - April, 2008

Dr. Tony K. Wolf, Viticulture Extension Specialist, AHS Jr. Agricultural Research and Extension Center, Winchester, Virginia

Table of Contents

  1. Pest management reminders
  2. Fungicide resistance update (A. Baudoin)
  3. Norton spray program
  4. Grape insecticide updates (D. Pfeiffer)
  5. Upcoming vineyard meetings

I. Pest management reminders

The low temperatures in northern Virginia over the past weekend reminded me of the spring of 1993 when we had lingering snow on the ground on 1 April. It was cold, but not unusually so. Our average budbreak date for Chardonnay at Winchester was 21 April for the period 1989 through 1999. We appear to on track for that date again this year. Buds were just starting to break on Petit Verdot in a southeast Virginia vineyard yesterday (31 March) and that vineyard is typically 3 to 4 weeks ahead of us here at Winchester.

The following bulleted discussion offers a very brief highlight of pertinent pest management issues in Virginia vineyards in the coming 4 to 6 weeks. I’ll expound upon the pre-bloom through bloom period issues in the next (May-June) Viticulture Notes. The focus here is on early season diseases, however, a few comments on climbing cutworms and flea beetles are included.

First, some more in-depth sources of information on disease management.

Virginia Cooperative Extension’s 2008 Grape Pest Management Guide (PMG) can be downloaded at:  The Virginia Cooperative Extension pesticide recommendations are annually prepared by pest management specialists at Virginia Tech. Pesticide recommendations augment cultural control practices, including integrated pest management of arthropod pests and good canopy management techniques to set the stage for effective disease control. Additional disease management recommendations can be found in past issues of Viticulture Notes, available through my website (, in the Compendium of Grape Diseases (, and by attending regional vineyard meetings, some details of which are listed later in this newsletter.

Early-season pest considerations

Climbing cutworms and flea beetles:


Black rot:

Powdery mildew:

Downy mildew:

Table of Contents

II.Fungicide resistance update 2008 (powdery and downy mildew)

Anton Baudoin, Department Plant Pathology, Physiology and Weed Science, Virginia Tech

For the past several years, we (a fancy way of saying: my graduate student, Jeneylyne Colcol) have tested samples of powdery and downy mildew from Virginia vineyards for sensitivity to commonly used fungicides. We have reported some of this information earlier, but the results are now based on many more samples, which has increased our confidence.

First, the strobilurins, Abound, Sovran, Flint, and the strobilurin component of Pristine: the majority of isolates of both powdery and downy mildew obtained from commercial vineyards in the mid-Atlantic region are strobilurin resistant.  Sensitive strains are still found on backyard grapes, in vineyards that have not been treated with this group of fungicides, and occasionally, as part of a mix, in vineyards that have been commonly treated. Control failure does not always occur; we have sampled in vineyards where no one has reported any particular trouble or control failures, but even there, the majority of isolates are resistant to both powdery and downy mildew; other fungicides must be doing the job.

Based on this situation, we no longer recommend this group of fungicides for grape powdery or downy mildew control in Virginia under most circumstances, although they probably retain effectiveness against other diseases, such as black rot.  Even in vineyards with sensitive populations, or where strobilurins have not been used previously, now that a high percentage of what's blowing around in the air is probably resistant, it would not require many applications to select a resistant population. Someone who has used a strobilurin just a couple of times over the last few years may well develop a resistance problem due to influx from a vineyard 10 or 20 miles down the road or across the hill. In this light, we would suggest only using strobilurins for powdery or downy mildew in vineyards with no or very little strobilurin history, and then only for an occasional spray. And always tank-mix with a different fungicide that is active against the disease in question (e.g., sulfur against powdery mildew).

The one exception is the use of Pristine against powdery mildew.  Pristine contains a strobilurin component, but also a second active ingredient, boscalid. The good news: all our grape powdery mildew isolates have been sensitive to boscalid.  But in vineyards with strobilurin-resistant isolates, Pristine is now equivalent to Endura (which contains boscalid only) for powdery mildew control.  The labels allow a maximum of 3 Pristine and 3 Endura applications per season, but for powdery mildew, this should be interpreted as 3 applications total (2 may be better). Pristine will not control strobilurin-resistant downy mildew, since boscalid has little activity against downy mildew.  Resistance development to boscalid is clearly possible: a recent report on Alternaria blight of pistachio in California found field sites where boscalid (as Pristine) had been used at two or three sprays per season for two consecutive years, and where 7 of 59 fungus isolates recovered had a high degree of resistance (Avenot, H.F., and Michailides, T.J. 2007. Plant Disease 91:1345-1350).

More good news: all our powdery mildew isolates have been sensitive to quinoxyfen (Quintec) as well.  But this is also a compound with expected resistance risk, so applications should be limited.  The labels limit the number of applications to five per season, but I would be more comfortable with about two or three.

Our results with sterol inhibitor fungicides (Elite, Orius, Nova=Rally, Rubigan, Procure) suggest that people who have used Nova/Rally or Elite/Orius on a regular basis, have a good chance of having a good proportion of powdery mildew strains with distinctly reduced sensitivity.  Such strains grow on leaves treated with 10 to 30 times the minimum concentration that would stop sensitive isolates, but high (labeled) rates and shorter intervals would still be expected to provide a reasonable level of control; how much exactly is uncertain.  In our isolates (and this agrees with reports from elsewhere), the shift to Rubigan sensitivity was much less pronounced, and powdery mildew control is likely to benefit (at least for a while) from a switch to Rubigan, especially where Rubigan has seen limited use recently.  Rubigan is inexpensive, but do take into account that its efficacy against black rot is less than that of Elite or Rally.  Interestingly, but an academic issue because it has been discontinued, we also found generally high sensitivity to Bayleton. This was somewhat surprising since Bayleton was commonly used in earlier years, and previous reports had indicated that reduced sensitivity was likely to persist in the field due to pressure from other sterol inhibitors.  If you still have some Bayleton with a grape label sitting around, you are allowed to use it up, and it may well be one of the better (sterol-inhibitor) choices for powdery mildew control at this time.

One new product, Adament 50 WG, is a mixture of 25% trifloxystrobin (active ingredient in Flint) and 25% tebuconazole (active ingredient in Elite).  The powdery mildew rate is 3-4 oz/A, but if you have QoI resistance, the tebuconazole will have to carry the entire work load, and 4 oz. of Adament contains only the amount of tebuconazole equivalent to 2.2 oz. of Elite. You would want to use the highest labeled rate (7.2 oz/A, listed for Phomopsis, Black rot and Botrytis), to get tebuconazole equivalent to Elite at its highest label rate (4 oz.).

Other powdery mildew fungicides include sulfur, horticultural oil, biofungicides such as Sonata and Serenade, Armicarb, Nutrol, and several others, which we have not tested in our resistance assays since they are thought to be multi-site fungicides and have low resistance risk.  One additional single-site fungicide labeled for powdery mildew control is Topsin M; we have only tested it with a very few isolates, but the results have not been encouraging: most isolates tested appeared to be completely resistant.

Also some good news about downy mildew: all isolates tested have been sensitive to mefenoxam (Ridomil), so this continues to be an excellent option.  Disclaimer: past performance is no guarantee of future results; mefenoxam DOES carry a distinct resistance risk if overused, but it suggests that Syngenta’s strategy of selling it only as a prepack mix with a multisite fungicide, and making it pretty expensive so growers are not inclined to apply it too often is working.  An additional, completely new downy mildew fungicide from Syngenta very recently had its registration approved by the EPA: mandipropamid (Revus). I don’t know when it will become available in a store near you, but this should also become a very effective downy mildew option … if not overused.

A considerable number of multi-site alternatives as well as Gavel (discussed last year), are available as well.  Multi-site fungicides for downy mildew control include copper materials, potassium phosphite (e.g., Prophyt), mancozeb, captan, and ziram, but it IS unfortunate that there is nothing that controls both powdery AND downy mildews like the strobilurins did!

For Endura/Pristine, Quintec, and Ridomil, we would be interested in hearing from people who have used these materials on a somewhat regular basis, especially if and when they see some disease “peek through”.  Testing samples from such situations may provide early warning of any developing problems.

Support from the Virginia Wine Board, Viticulture Consortium-East, and the Virginia Agricultural Council are gratefully acknowledged for this research.

Table of Contents

III. Norton spray program

Our canopy management and chemical (fungicide) approach to grape disease control in Virginia is often aimed at the most susceptible cultivars (V. vinifera) and our primary fungal diseases (mildews, black rot, phomopsis and botrytis). To the uninitiated, the recommendations might also be used on hybrids and American-type grapes, the latter including Norton (V. aestivalis). To do so, however, would be a costly and unnecessary program, at least from the standpoint of the fungicide applications (the canopy management recommendations would generally hold true, across cultivars/species).  Experienced growers of hybrid grapes know that some of the sprays used on vinifera can be sprayed much less frequently and still result in an effective spray program. A question recently arose about “standard” spray schedules for V. aestivalis, Norton. My recommendations at “Basic, new grower” workshops when discussing variety options, were that one of the advantages of Norton was that one could use a very reduced disease management program with the variety (2 to 3 sprays per year) as compared to 10 to 12 often used on a hyper-sensitive variety such as Chardonnay. Norton is considered moderately susceptible to downy mildew and slightly susceptible to powdery mildew, phomopsis, black rot and botrytis. In my own experience, I have seen very small powdery mildew lesions develop on Norton leaves late in the season, but the lesions did not significantly enlarge and never warranted a fungicide spray.  Other growers have reported substantial downy mildew occurring on unprotected Norton vines in wet years. And, as we reported in the September-October 2000 Viticulture Notes, we saw an appreciable amount of zonate leaf spot, caused by the fungus Cristulariella moricola, in late-summer on unprotected Norton.

 In response to a question from Scott Elliff, a Madison County (VA) Norton producer, we asked a range of Norton growers what their actual spray programs and experiences were with Norton. Scott solicited the spray information and I offered to summarize the programs used (Table 1). The survey was non-exhaustive; it included only 8 growers, including our own Norton spray program at Virginia Tech’s research vineyard in Winchester.

The surveyed growers reported what fungicides they used on bearing Norton vines during each of the 2006 and 2007 growing seasons – 2006 was relatively wet while 2007 was relative dry; a representative contrast.  The range of fungicides used was surprising. Two growers reported using no fungicides in either year, with no disease reported. On the opposite end of the spectrum, one grower (vineyard 5) used an extensive spray program that exceeded $100/acre in material costs alone.  All 8 respondents indicated that they had effective disease management – even those who report using no fungicides. This then begs the question, Are fungicide applications necessary on Norton?  Possibly not, if you are willing to mind the weather and do not mind taking some risks. Given Norton’s moderate susceptibility to downy mildew, I would not skimp on one or two prophylactic sprays in the pre-bloom to immediate post-bloom period. It makes sense to use relatively inexpensive but effective products, such as captan or mancozeb. Extra protection, at added material cost, might be afforded by systemic materials such as mefenoxam (e.g., Ridomil), phosphorus acid (e.g, ProPhyt), or mandipropamid  (Revus), or via the extended weathering resistance feature of proprietary mancozeb products (e.g., Dithane Rainshield). Mancozeb would have the added benefit of providing black rot protection (again, Norton is only slightly susceptible to black rot).



Fungicides and number of applications/season


Material cost/acre


Mancozeb (3-4x)
Elite (1x)



No fungicides



Elite (3x)
Abound (1x)
Mancozeb (2x)
Captan (2x)
Prophyte (1x)



(unstated number)



Mancozeb (5x)
Abound (1x)
Captan (2x)
Pristine (1x)



No fungicides



Mancozeb (3x)
Captan (1x)



Elite + Prophyt (2x)
Mancozeb + Quintec (2x)

$42 to $55




Table 1. Fungicides used and approximate
material cost/acre for management of
diseases in Norton vinyards (Vyd)
during average year.

In the post-bloom period, the need for a protective fungicide could be gauged by rainfall or wetting patterns. An additional mancozeb or captan spray would be helpful if conditions were conducive for downy mildew development (frequent wetting periods), or an eradicant (e.g., phosphorus acid or Ridomil) could be used if you slipped on the protection. Given the concerns with widespread resistance issues, there would be little point in using Abound or other stand-alone strobilurins for downy mildew. The use of Pristine, while offering broad-spectrum control of many diseases, is an expensive alternative to older fungicides that offer similar protection in average rainfall years.  The pre-bloom through immediate post-bloom, two-spray program could be augmented with an additional spray or two, if needed, mid-summer if zonate leaf spot symptoms began to appear, or if the vineyard had a history of zonate leaf spot in the absence of such sprays.  Zonate leaf spot affects a range of woody and herbaceous plants and produces dime- to quarter-sized lesions that may lose their central area of tissue as they expand (Figure 1). Individual lesions consist of a series of concentric rings of alternating dark and light shades of brown or gray (Figure 2).

Figure 1

Figure 1. Zonate leaf spots symptoms on Norton, August 2000.

I have only seen the symptoms on foliage and, as the disease name implies, it largely or entirely affects leaves, as opposed to fruit. Interested readers can learn more about this disease at: Protective fungicides effective against zonate leaf spot include mancozeb and thiophanate methyl (e.g. Topsin M). Strobilurin fungicides may also be effective (the fungicide efficacy data for zonate leaf spot is… spotty), but this would be a more expensive route than simply making a thiophanate methyl or a mancozeb spray if prolonged wet weather occurs. Remember, mancozeb carries a 66-day pre-harvest interval; Topsin-M carries a 14-day PHI.

Norton growers are reminded that Norton is also susceptible to grape berry moth and Japanese beetles, so appropriate insecticide sprays might be needed, even in the absence of fungicides for disease management.

Thanks to Scott Elliff for pulling the survey information together for this note.

Figure 2

Figure 2. Individual zonate leaf spot lesion.

There are additional, regional sources of disease management information that are freely available and very useful. Dr. Wayne Wilcox of Cornell University, who is no stranger to Virginia growers, has updated and issued his annual grape disease roundup of recommendations. As in previous years, Dr. Wilcox offers a comprehensive review of new fungicide updates, a smattering of recent research results, and a compilation of how the information can be integrated into a season-long program. I’ve attached a pdf version of Dr. Wilcox’s 2008 report for your perusal.

Another excellent regional resource is Dr. Anne DeMarsay, small fruits pathologist with the University of Maryland. Anne produced a very practical, user-friendly wine grape spray schedule last year (2007), annotated with various recommendations on timing, pitfalls, and need for rotation of materials for resistance management. Anne may have an updated version in the works, but in the meantime, the 2007 version is still very instructive, particularly for new growers. To view, go to Joe Fiola’s grape web pages ( and scroll down to Pest Management. The spray schedule is entitled, “Guidelines for Developing an Effective Fungicide Spray Program for Wine Grapes in Maryland, 2007”.

Table of Contents

IV. Grape insecticide updates

Doug Pfeiffer, Department of Entomology, Virginia Tech

New insecticides for grapevines:  There have been several important additions to the tools available in the Pest Management Guide.  We now have a new material in the same mode of action class as spinosad (SpinTor).  The new product will be more effective and long-lived.  This is spinetoram (Delegate).  This will be used for grape berry moth (GBM).  Baythroid XL (cyfluthrin) is now registered, used for GBM, grape leafhopper, mealybugs, grape flea beetle and climbing cutworms.  Avaunt (indoxacarb) is now registered on grape.  This material, a representative with novel chemistry, has been used in some other crops for some time, but is newly available in grapes.  Avaunt is effective against GBM.
A formulation of bifenthrin, Capture 2EC, formerly was registered in grape (now registered only in California).  This formulation is now replaced by Brigade (same active ingredient) and will be used in the same places and rates as Capture in the 2008 Pest Management Guide.
Neonicotinoids for sharpshooters - Several neonicotinoids are available for control of sharpshooters, the vectors for Pierce's disease.  Venom is more soluble than imidacloprid, and is more rapidly taken up by vine.  Rapid movement of material to tissues is important, since PD infection can occur from only an hour's feeding.  In addition to the pyrethroids, Brigade replaces Capture, and Baythroid is now registered.  I do not recommend spraying for sharpshooters unless a significant risk of Pierce's disease exists.  I have posted information on the number of cold nights this winter, an important factor in determining risk, according to Virginia Tech weather stations spread throughout the state.  Consult this information to aid in PD decision-making (

Table of Contents

V.   Upcoming meetings

Vineyard meetings in Virginia

A series of vineyard meetings, arranged by Virginia Cooperative Extension Agents, are planned for the period from April through July. The meetings generally include one to several grape specialists with Virginia Tech and the agents may provide presentations as well. Most meetings include an overview of the vineyard activities by the owner/operator of the host vineyard. The dates at this point are as follows (unfortunately, I was not able to obtain specific meeting information at the time this newsletter was issued for the central and northern Piedmont meetings).

Central Virginia
April 11:            Ivy Creek Vineyards
May 9               Delfosse Vineyards
July 11              Pollak Vineyards

For Directions, specific program topics, speakers, and other details, contact: 
Michael Lachance
Virginia Cooperative Extension-Nelson County
Voice:    (434) 263-4035

Southwest Virginia 
Date:    April 30, 2008
Location:   Chateau Morrisette (meet at winery)
Time:   10am – 2pm, or later
- early season disease management issues
- shoot thinning and other early season canopy management considerations
- vine nutrition reminders

Lunch provided by Chateau Morrisette; however, pre-registration is required for lunch. Check made payable Floyd Extension Office @ $15/person (for lunch). Mail registration in advance to:

Floyd Cooperative Extension,
209 Fox Street NW, Floyd, VA 24091
Further information: 540 745-9307

Directions:  From Roanoke: Take Rt. 220 to the Blue Ridge Parkway South, watch for milepost 171, proceed approx. ½ mile and take a right onto Black Ridge Road and then an immediate left onto Winery Road. Chateau Morrisette is located approx. 300 yards on the right.

From Floyd: Take Rt. 221 South to Floyd, at the stoplight in Floyd turn left onto Rt. 8 South, proceed approx. 6 miles until you see an entrance sign onto the Blue Ridge Parkway in Tuggles Gap, head South on the Parkway, watch for milepost 171, proceed approx. ½ mile and take a right onto Black Ridge Road and then an immediate left onto Winery Road. Chateau Morrisette is located approx. 300 yds. down Winery Road.

Northern Piedmont meetings
Only the dates are set at this point, as follows:

April 23
May 21
June 25
July 30

More information can be obtained from:
Kenner Love
Rappahannock County Cooperative Extension
(540) 675-3619

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:

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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