Module II: Grapevine Diseases & Varietal Traits

• This study note covers the examination-relevant slides from Module II, focusing on grapevine diseases, varietal characteristics, vine training, and viticultural practices.

Reblaus (Grape Phylloxera) History

• First appeared in Germany in 1874 near Bonn along the Rhine, and in 1885 near Dresden.
• Spread to most German winegrowing regions.
• Damages roots of European grapevines, leading to the slow death of the vines.
• Caused severe economic weakening or destruction of many vineyards.
• Originates from North America, where certain native grape species are resistant.
• European vines adapted over centuries to resist phylloxera damage.

Differentiating Grape Varieties Based on Yield

• Distinguishable varietal characteristics:
  • Shoot tip appearance
  • Bud break and flowering time (scent)
  • Leaf characteristics (color, shape, sinus)
  • Grape and berry appearance
  • Susceptibility to disease and yield data
• Ampelography (Rebsortenkunde): the science of identifying and classifying grape varieties.
• Multiple thousands of grape varieties described, making classification complex.
• Classification is difficult due to synonyms across regions and variations in growth.

Origin of New Grape Varieties

• Historical: selecting wild vines or chance crossings exhibiting desired traits; propagated vegetatively through cuttings ("Stecklinge"). Traditional grape varieties such as Traminer, Burgunder, and Riesling came about this way.
• Natural: mutation, random alterations of the genetic material in a bud or through sowing grape seeds, resulting in mutations in varieties like Grau-, Weiß- and Spätburgunder, Schwarzriesling, Samtrot Kerner, Kernling, Weißer Riesling, and Roter Riesling
• Contemporary: the deliberate crossing of grape varieties to combine desirable traits in offspring, such as stable yield, high wine quality, frost resistance, and disease resistance. Müller-Thurgau was the first systematically bred variety, but current breeding focuses almost exclusively on resistance to fungal diseases.

What is a "Klon" (Clone)?

• Grapevine planting material is exclusively propagated vegetatively via cuttings or grafting, resulting in genetically identical plants.
• Descended from a single mother plant; these identical offspring known as KLON (clone).
• Clone establishment and preservation breeding: Selection of individual vines of existing varieties known to have exceptional traits (yield, quality, health, grape structure).
  • Involves observation, evaluation, and selection over several years, discarding insufficiently satisfactory breeding lines.
  • Registration of a clone in the clone registry of the Federal Plant Variety Office, establishment of propagation facilities for plant production with annual post-selection.
  • Germany only brings virus-tested (healthy, virus-free) and clonally pure propagation material into circulation.

Pilzfeste Sorten (Fungus-Resistant Varieties)

• Crossings between European and American vines, repeatedly backcrossed with European varieties.
• Designed to eliminate the distinct "hybrid tone."
• White varieties:
  • Calardis blanc
  • Solaris, Johanniter
  • Cabernet blanc
  • Sauvignac
• Red varieties:
  • Regent
  • Cabernet Cortis, Pinotin, Cabertin
  • Satin Noir

Top Three White Grape Varieties of the Pfalz

• Weißer Riesling (5850)
• Müller-Thurgau (2026)
• Ruländer (Grauburgunder) (1547)

WEISSER RIESLING Characteristics

• Origin: likely spontaneous seedling of wild vine; one parent is Heunisch, the other is Vitis silvestris x Traminer.
• Germany (Deutschland) and Pfalz: most important and well-known white wine variety.
• Site (Standort): demanding; optimally ripens mid-late season.
• Wine type (Weintyp): high acidity, delicate flavors, citrus-peach-maracuja aromas, "King of White Wines," highly terroir-driven.
• Historical significance; documented for over 500 years as "Ruessling".

Winter Vine Pruning

• Grape vines are liana-like plants with a physiological structure that prioritizes the uppermost buds (apical dominance).
• 90% of new wood (one-year-old wood) removed during winter pruning.
• Cuts in perennial wood should be minimized.
• Pruning has two goals:
  • Training (Erziehung): shaping young vines to establish a growth habit (constant over the yield-bearing period)
  • Yield Regulation (Ertragsregulierung): reducing the number of buds to control fruit yield.

Summer Canopy Management

• Goals of summer canopy management:
  • Brake/regulate vegetative growth.
  • Summer pruning slows growth, while winter pruning supports it.
  • Stabilize the foliage wall, prevent shoots from bending or breaking
  • Prevent self-shading
  • Ensure accessibility, prevent the canopy walls merging together, and promote air circulation.
  • Allow optimal plant protection application.

Berry Development Stages

• Veraison begins as grapes ripen.

Determining Grape Maturity

• Sugar content
• Acidity (tartaric acid, malic acid, pH)
• NOPA (yeast assimilable nitrogen)
• Taste of berries (sensory evaluation)
• Physiological ripeness

Bodenpflege (Soil Management)

• Soil management should be tailored to site-specific conditions.
• Consider the volume and distribution of precipitation
• Soil type, gravel content, and depth.
• Water storage capacity and field capacity.
• Temperature patterns and solar radiation.
• Slope angle and aspect.
• Erosion susceptibility.
• Accessibility.
• Soil management practices should be adaptable, especially in response to weather conditions.

Grapevine Moth Control (Biotechnical)

• Pheromone confusion technique disrupts mating.
• Natural mating behavior:
  • Female moths release sexual pheromones
  • Forms a “pheromone trail”
  • Males fly to females via the pheromone trail
  • Mating and reproduction
• Disruption with confusion method:
  • Artificial pheromone cloud made using dispensers
  • Males cannot find females (no pheromone trail exists)
  • No mating → no reproduction

Kirschessigfliege (Spotted Wing Drosophila) Damage

• The female can use its ovipositor to puncture ripe, healthy berries and lay eggs just under the skin.
• Hatched larvae feed on the pulp inside the fruit.
• This often leads to soft, depressed spots on the berry.
• Secondary infections caused by pathogens regularly occur.

Spotted Wing Drosophila Control & Prevention

• Apply indirect preventative measures, like exposing grapes by removing leaves in high-risk vineyards before ripening.
• Ensure a well-ventilated canopy.
• Keep groundcover short beginning at the onset of ripening.
• Use approved insecticide when necessary; consider bee protection measures.

Spotted Wing Drosophila Symptoms

• Experienced observations show that the Drosophila preferably infests red grape varieties.
• White grape varieties typically undamaged.
• Lightly colored white grape varieties may be affected in some cases.

Promoting Beneficial Insects in Vineyards

• Use cultural techniques:
  • Diverse vegetation (allow flowering)
  • Alternating soil cultivation (permanent vegetation when possible in the second row)
  • Diverse vineyard structure (hedges, green strips, uncultivated land, etc.)
• Use chemical protection methods:
  • Reduce to the minimum necessary
  • Choose selective, non-toxic products
  • Consider alternative actions

Phenolic Content in Grape Parts

• Skin contains the most phenolic content followed by:
  • Seed flesh, stem, pulp, and pulp

Mostgewicht (°Oechsle) - Must Weight

• Oechsle (°Oe) is Germany’s common density measurement for the weight of grape must.
• °Oechsle = (specific gravity - 1) x 1000
  • Ex: 85 °Oe = (1.085-1) x 1000 = 85 g
• One liter of must weighs more than one liter of water.
• One liter of must with 85 °Oe weighs the same as 1.085 liters of water at 20°C.

Aromastoffe (Aroma Compounds)

• Grape aroma compounds = Primary aromas (different from secondary and tertiary aromas in wine).
• Sulfur dioxide (SO2) in grapes and must:
  • Inhibits bacteria and wild yeasts.
  • Suppresses oxidation reactions.
  • Provides oxidation protection.
  • Binds with sensory-relevant byproducts of alcoholic fermentation in wine.
• Bacteria that perform biological acid reduction produce lactic acid from malic acid and give positive aromas.

Reasons for Initiating Fermentation with Pure Yeast Cultures

• Pure yeast cultures are derived from one single yeast cell.
• Guarantee the onset and consistent fermentation.
• Provide pure notes (lower danger of wine defects).
• Promote consistent varietal traits.
• Reduces the development of unrequested by-products.
• Requires less need for nutrients.
• Vital to ensure the wine quality matches the must quality.

Wine Taste Classifications

• Trocken (Dry):
  • up to 4 g/L residual sugar (only in the Franconia growing area)
  • up to 9 g/L residual sugar, where the acidity can be 2g/L lower, and the formula is: acid + 2 maximum 9g/L
• Halbtrocken (Medium-Dry):
  • up to 18 g/L residual sugar, where the acidity can be 10g/L lower, and the formula is: acid + 10 maximum 18g/L
• Lieblich (Semi-Sweet):
  • up to 45 g/L residual sugar
• Süß (Sweet):
  • more than 45 g/L residual sugar

Enrichment (Chaptalization)

• Increases the alcohol content if the must itself does not contain adequate sugar.
• Permissible only with quality wine (g.U.), country wine (g.g.A), and German wine.
• Enrichment forfeits the right to label the wine as Prädikatswein (Kabinett, Spätlese, Auslese, Beerenauslese, Trockenbeerenauslese, and Eiswein).

Oenological Methods

• Mash fermentation or -heating;
• Must concentration;
• Saignee (bleeding) for more color and tannin structure
• Kaltmazeration (cold soak) for better Gerb- und Farbstoffverhältnnis;
• Fermentation (duration, temperature, whole cluster inclusion)
• Extraction of the seed during Spätburgunder for extended maceration;
• Oxygen supply and tannin use
• Use of wood and micro-oxygenation

Guidelines for Moderate Wine Consumption

• Guidelines vary by country; however, studies show general guidance on doses to consume with minimal risk.
• Low-risk dose:
  • Women: Up to 2 standard drinks (20 g of alcohol) per day.
  • Men: Up to 3 standard drinks (30 g of alcohol) per day.
• Never consume more than 4 standard drinks (40 g) on any occasion and to incorporate one or two alcohol-free days per week.

Alcohol Content

• Alcoholic beverages contain distinct amounts of alcohol.
• One unit contains approximately 10 g. of pure alcohol.

Healthy Drinking Habits

• Limited drinking habits are important to maintain a healthy moderation.
• 200 ml of wine is a healthy amount for women and 300 ml for men.
• Drinking with and during a meal is also recommended to make the wine more palatable.

Alcohol Metabolism

• Individual metabolism rate for alcohol varies.
• The average person metabolizes 0.1-0.2 ‰ per hour.
• Women’s blood alcohol content generally rises higher than men’s.

Serving Temperature

• Sparkling wine should be served at 8-10° Celsius.
• Light, young white wine should be served at 9-11° Celsius.
• Full-bodied white wine is best served at 11-13° Celsius.
• Rosé/Weißherbst should be served at 9-13° Celsius.
• Light, young red wine should be served at 14-16° Celsius.
• Red wine gehaltvoll is best served at 16-18° Celsius.
• High aromatic and tannin red wine should be served at 18-20° Celsius.

Tasting Wine

• Assessing the color
• Smell of the unswirled wine
• Smell after brief swirling
• Smell after intense swirling
• Mouthfeel and assessment of basic flavors
• Retronasal flavor impression
• Finish, aftertaste, and persistence

Ways to Perceive Smell and Retronasal Aromas

• Orthonasal perception occurs through the nostrils.
• Retronasal perception occurs when aromas travel to the olfactory bulb through the back of the mouth while chewing.

Pairing Wine and Cheese

• White wines generally pair with cheeses better than red wines.
• Pair what tastes good.
• The cheese and wine should be of similar strength.
• Pair light cheeses with light wines.
• Delicate cheeses pair with delicate wines.
• Strong cheeses pair with stronger, bolder wines.

Pairing Food and Wine

• Harmonious: Bitter/Salt, Puffer/Sweet, Salt/Sweet, Sweet/Sour
• Neutral: Sweet pairings
• Unharmonious: Sour/Bitter, Bitter/Bitter, Salty/Salty

Pairing Wine and Chocolate

• Pair high cacao with high alcohol
• Pair light Schokolade with light wine