Fungicide applications affect fruit diseases and quality of muscadine grape

Another teaser for the 2013 Muscadine Field Day — see the abstract below provided by Dr. Barbara Smith, USDA-ARS Plant Pathologist.

Fungicides can significantly reduce losses due to disease in the yield and quality of muscadine grapes. In four studies fungicides were applied individually or as part of a full season schedule from early bloom until harvest to three muscadine grape cultivars. The objective was to compare the effect of a full season treatment of 9-12 fungicide applications applied on a 10-day interval to fewer applications of individual fungicides on disease incidence, yield, and berry quality. Foliar and berry diseases were rated on visual scales. Sugars, acids, ellagic acid, and resveratrol content were determined by HPLC.

Four studies explored the relationship between disease control, berry quality, and phytochemical content following full season or early season application fungicides.  In each study foliar and fruit diseases were lower in the full season treatment compared to the control, each fungicide was effective in reducing at least one disease, and some treatments with fewer applications reduced fruit diseases to the same level as the full season treatment.  In Study 1, the full season treatment of 9 applications applied at 10-days intervals and the azoxystrobin treatment of 3 applications applied at 30-day intervals resulted in significantly higher yields, lower fruit disease scores, and more asymptomatic berries than the control treatment.  In Study 2, four applications of the azoxystrobin, myclobutanil, and the combination fungicide, cyprodinil plus fludioxonil applied at 30-day intervals were as effective in reducing total berry diseases as the full season schedule of 12 applications (three fungicides alternated at 10-day intervals).  In Study 3, three fungicides were applied on an alternating schedule every 10 days beginning at bloom and stopping at various pre-harvest intervals.  There were no significant differences in vine vigor, foliar diseases scores, percentage of asymptomatic berries, or bitter rot scores due pre-harvest interval.  In Study 4, there was not a significant difference in the percentage of asymptomatic berries between the full season treatment of eight applications and early season treatment of four applications or in the bitter rot and total disease scores for five of the fungicide treatments.  Data indicate that fungicide applications can be stopped as early as six weeks before harvest without significant effects on berry diseases.

Studies 1 and 3 also investigated the effect of fungicide treatments on berry quality and phytochemcial content.  In Study 1, significant differences were found in pH, TA, fructose, glucose, tartaric acid, and resveratrol levels.  Total resveratrol was lower in the skins of berries from the full season and azoxystrobin treatments than from the control and other fungicide treatments.  Berries from the least efficacious treatments for berry diseases had almost ten times as much resveratrol as those from the full season and azoxystrobin treatments.  In Study 3, ellagic acid content was lower in berries from the spray treatment than from the not sprayed and control treatments.  Total resveratrol content was approximately four times higher in skins of berries that did not receive fungicide sprays than in those that did.  Resveratrol levels in the skins of berries from fungicide treatments were very low even if the last fungicide application was 8 weeks before harvest.

Data from these four studies indicate that the number of fungicide applications required for control of muscadine grape diseases can be reduced without an increase in berry rot disease severity.  The most effective fungicides reduced berry diseases with as few as four applications compared to 12 applications in the full season schedules.  Fungicides that controlled berry disease had an effect on berry quality including lowering the content of the beneficial phytoalexin, resveratrol.

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2013 ASEV-ES Red Wine Symposium

On July 18, 2013 at the American Society for Enology and Viticulture, Eastern Section Conference in Winston-Salem, NC I attended the Symposium on Advances in Red Wine Production: Berry to Bottle.  The speakers included Diego Barison (NovaVine), Tony Wolf (Virginia Tech), Michael Jones (Scott Laboratories),  James Kennedy (Fresno State), James Harbertson (Washington State), Sara Spayd (NC State), and a panel of growers from NC, TN, and VA.  The Symposium started off with a welcome from ASEV-ES Chair Fritz Westover.

 

Fritz Westover gets the Symposium started

Fritz Westover gets the Symposium started

The first speaker, Diego Barison gave a talk entitled “Latest News on Red Wine Varieties for Warm Climates”.    He spoke on the need for clonal selection to preserve genetic variability, preserve infrequent characteristics, to make more complex wines, and to exhibit weaker genotype by environment interactions.  One of his jobs is to look for characteristics that may be suitable for clonal establishment, such as loose clusters that minimize susceptibility to disease.  Any new clones are grafted to indicator rootstocks to determine if viruses are present.  Eventually microvinification and sensory analyses are carried out to see if the clone is suitable as a wine.  Some of the goals he mentioned for his program are grape acidity, ripening period, color, crop load, vigor, clean plant material, adaptability to blending, adaptability to environment, and its cultivated history.  He mentioned some new clones derived from Sangiovese, Montepulciano, Teroldego, Aglianico, Negro amaro, and Calabrese that may be available in the future to growers.

Diego Barison from NovaVine

Diego Barison from NovaVine

The second speaker was Dr. Tony Wolf and he covered “Canopy Management Advances for Red Wine Grapes”.    Canopy management is a set of practices which can be used to alter the number, arrangement and development of shoots in space and time and thereby affect the canopy and cluster microclimate.  It is often aimed at improving the architecture of canopies under supra-optimal growth conditions.  Common goals of canopy management are: improved fruitfulness, improved grape composition, improved wine quality potential, decreased disease incidence/severity, and to facilitate mechanization.  Canopy modification can have direct and indirect effects.  A direct effect is one that alters arrangement of leaves and clusters such as training system, pruning, thinning, positioning, and shoot/leaf/cluster removal.  Indirect effects are those the affect the canopy density by controlling things like shoot vigor, lateral shoot development, and duration of shoot growth.  This is accomplished through management of irrigation, choice of rootstock, site selection, cover cropping, and root containment/root pruning.  An indicator of an out-of-balance vine is greater than 1.0 kg of prunings per meter of canopy (about 0.4 lb/ft).  Desired canopy goals are 1 square meter of leaf area per kg of fruit and 12-15 shoots per meter.  Other desirable attributes of a balanced canopy post-bloom to veraison in red varieties are: about 20% gaps in the canopy, 1 to 1.5 leaf layer, 3-4 shoots per foot (VSP system), 12-20 fully unfolded leaves, 5% or less active shoot tips by veraison, 50% or more cluster exposure to light on East side (less on West; maybe more for high acid varieties), few lateral leaves in the fruiting zone (less than 10 on basal 7 nodes of each shoot by veraison), and 0.3-0.6 kg fruit/meter of canopy.

Tony Wolf discussing canopy management in red wine varieties

Tony Wolf discussing canopy management in red wine varieties

Since these were the two “viticulture” talks of the symposium they were primarily the ones I took notes on; however, I do have a few more.

The third speaker was Michael Jones from Scott Labs.  He spoke on “Stuck and Sluggish Fermentations”.  The primary causes of stuck and sluggish fermentations are: nutrient deficiency, competition from wild yeast/bacteria, lack of survival factors (long-chain fatty acids, sterols), ethanol, temperature, osmotic shock, toxins, inadequate yeast populations, highly clarified must, and pesticide residues.

The next speaker was Jim Kennedy from Fresno State on the topic of “Phenol 101”.  I recall this talk was heavy in biochemistry.  He described that anthocyanins are largely found in the skin along with flavonols.  Hydroxycinnamic acid is in the pulp.  The tannins in the grape are made prior to veraison.  The tannins mature along with anthocyanins post veraison.  Moderate stress tends to increase phenolic quantity and quality, including high sun exposure, low nitrogen, low soil moisture, moderate canopy size, and moderate crop load.  Fruit exposure to the sun is positively related to wine quality.

The next two speakers, Jim Harbertson (Washington State) and Sara Spayd (NC State) also spoke about phenols (“Improving Red Wine Color and Phenols” and “Red Wine Phenols in North Carolina”, respectively).  However, I did not take any notes.  There was also a panel discussion on “Issues in Red Wine Production in the Southeast”.

My colleague Mark Chien from Penn State summarized some of these and other talks from the conference.  You can find that here: http://www.pawinegrape.com/uploads/PDF%20files/Temporary%20Files%20-%20delete%20often/asev%20es%2013%20notes.pdf.  See the entire program here: http://www.asev-es.org/pdf/2013%20%20Program%20ASEV-ES%20full.pdf.

You might also find Mark’s discussion with Steve Menke (Colorado State) and Sara Spayd of interest on growing fine wines in the East (http://www.pawinegrape.com/uploads/PDF%20files/Temporary%20Files%20-%20delete%20often/Sara%20and%20Stephen%20-%20wine%20quality.docx.pdf).

Generally most of the talks focused on Vitis vinifera varieties, as that is where most of the research has been done.  However, there was good info on interspecific hybrids and a little on muscadines as well.  I would encourage anyone with an interest to join ASEV-ES.  It is relatively inexpensive and the information that comes out of the meeting is great.  Plans are in the works to update the webpage, create a newsletter, and get involved with social media (primarily facebook).  If you are interested in more information and how to join go here: http://www.asev-es.org/index.php

 

Looking at Victoria Red

Earlier this year Jim Kamas from Texas A&M sent me a few vines of ‘Victoria Red’ to try here in Poplarville.  To my knowledge this variety has not been grown in this area before, so I was intrigued to see how it would do.  Below you can see a photo of what it looks like on May 15, 2013.

Victoria Red

‘Victoria Red’

So far it has grown well. They are on a rootstock.  I did notice some black rot on the leaves and another symptom that could be early black rot, although it resembles rupestris speckle.  The variety is difficult to find in the trade, as various setbacks to propagation have occurred in the last couple of years (i.e. the major drought in Texas).  Jim Kamas did a nice write up of the variety here: http://pd.tamu.edu/news/newsletter/2010-10.pdf

Some of the interesting things about ‘Victoria Red’ as stated by Jim Kamas:

“The most significant characteristic of ‘Victoria Red’ is its sustained health, vigor and productivity in Coastal Texas, an area of the United States with extremely high Pierce’s disease pressure. It is a seeded grape with bright red skin color and large, attractive clusters. The skin is tender and resists cracking at maturity due to rainfall. It has a primarily neutral flavor.”

“Both cluster size and berry size were outstanding in Victoria with clusters averaging 477 grams and berries averaging 8 grams. At the Victoria evaluation site, ‘Victoria Red’ averaged 9.1kg per vine on 8’ spacing in the row (20 lbs per vine or roughly 6 tons per acre). Average budbreak date was March 13th (about one day behind ‘Champanel’), average bloom date was April 20th, and typical harvest(using table grape parameters at 18ºBrix) was early July.”

“Victoria Red’ is recommended primarily as a fresh-fruit cultivar for on-farm and local-market sales in USDA hardiness zones 7b or warmer. It has however ripened in excess of 24ºBrix, making it a potentially valuable neutral blending wine grape for high PD risk areas.”

Thus, I am giving it a shot here in South Mississippi.  We certainly need another option for bunch grapes here.  My plan this year is to get it trained onto the wire and observe what happens to the vine — disease, insects, etc.  Next year a spray regimen will be followed and some hopefully some fruit to taste.