Viticulture Flashcards
What 3 factors can affect sunlight?
Latitude - Day length greater further from Equator
Seas, Lakes and Rivers - Near large bodies of water more cloud cover, Centre of landmasses tend to be sunnier
Aspect - A slopes aspect affect the amount of sunlight, steeper slopes = more benefit
What is the purpose of the California Heat Summation index?
How does this index work?
To classify vine-growing areas by temperature and thereby reccomend appropriate grape varieties for cultivation.
- Divides climates into five Regions based on the number of degree days.
- Degree days are calculated by multiplying the days in each month of the growing season (defined as April 1 through October 31) by the mean number of degrees over 50°F for that month.
- The months’ totals are then added together to arrive at the heat summation:
How does Phylloxera kill vulnerable vines?
How did Phylloxera first reach Europe?
- It feeds on the roots of the vine allowing infections to set in meaning, over the course of a few years, the vine dies.
- The louse came over on American vine cuttings that were imported to the Southern Rhone Valley in the 1860s.
The Picture Below is an example of what type of training?
Head Training
At what age are most vines replacedWhat are the pros / cons of ‘old vines’
Most replaced between 30~50 Years
Old vines produce higher quality fruit (more concentrated flavour) partly due to lower yield per vine.
Lower yield might not be cost efficient andolder vines more susceptible to disease
What climate type is this?
High Continentality, low rainfall and a very sunny growing season
Continental
Name 3 diseases that threaten vines and how they are controlled
Powdery and Downy mildew - Likes warm, humid environments. If affected grapes lose fruity flavour.
Powdery treated with sulfur based spray. Downy treated with Bordeaux mixture copper based spray. Can also be managed by canopy management to max air flow * More spraying in Maritime climates where there is more rainfall.
Black rot (Guignardia bidwelli) - The disease originates as a black spot on the vine’s shoots, leaves, and berries. Yield reductions can be disastrous if unchecked; it can be controlled through fungicide sprays.
New grape varieties can be created through cross pollination. What is ‘cross pollination’?
The pollen from the male part of the flower of one vine is transferred to the female part of the flower on another vine and fertilisation occurs.
Name the 2 most common training techniques for vines
Head training - Little permanent wood (some only trunk), then shoots are trained
Cordon training - Trunk plus one or more permanent horizontal arms (cordons). Takes longer to establish but makes mechanisation easier
What climate type is this?
Low to medium Contintality, low to medium rainfall mainly in Winter and a sunny growing season
Mediterranean
Identify 2 examples of Mediterranean Climate for the following temperatures:
Moderate
Warm
Hot
Mod -> Chianti, Carneros
Warm ->Chateauneuf, Napa Valley
Hot -> Murray-Darling, Calabria
Which soil type has the largest warming effect?
Gravel
Which of the following inputs to a vine will vary least from season to season?
CO2
Heat
Sunlight
Nutrients
CO2
Identify 3 methods of controlling the yield of grapevines:
Green harvest
Winter pruning
Irrigation
In which regions has Phylloxera not reached?
Why?
Chile, some parts of Argentina and South Australia.
Some parts of Lisboa, Portugal, due to sandy soils.
Some volcanic islands, such as Santorini.
It hasn’t reached due to strict quarantine procedures and inhospitable climate.
Why is vine bud management important?
What happens if there are too few / too many buds?
The vine stores Carbohydrates over Winter.
If too few buds each will have access to too much energy and will grow too vigorously.
If too many buds, each will not have access to enough energy and the vine will struggle to ripen its crop load.
What are 3 agricultural practices that reduce intense chemical usage?
Sustainable agriculture - Chemicals permitted but minimised by growers understanding life cycles of pests and introducing predators of the pests. Monitor weather to prevent pest or disease before it occurs.
Organic agriculture - Small doses of traditional treatments permitted only.
Biodynamic agriculture - Organic practices + philosophy and cosmology. Cycles of planets, moon and stars plus homeopathic treatments.
Put the growth cycle in order
Veraison, Budburst, Flowering, Fruit set, Ripening
Budburst, Flowering, Fruit set, Veraison, Ripening
Budburst, Flowering, Veraison, Fruit set, Ripening
Budburst, Veraison, Flowering, Fruit set, Ripening
Budburst, Flowering, Fruit set, Veraison, Ripening
How can VSP (Vertical Shoot Positioning) be used in hot, sunny climates and why would a grower choose to use this system?
The method is adapted so the tops of the shoots are not tied but allowed to flop over creating some shade in the canopy to protect fruit.
A grower would choose this system to enable mechanical harvesting.
Frost flows in a similar way to
Ice
Water
Steam
Water
Describe the annual cycle of vine
Spring
Late Spring / Early Summer
As Summer progresses
Late Summer / Early Autumn
Later in Autumn
Spring - Budburst, new shoots begin to grow
Late Spring - The vine flowers and small grapes form
Summer - Grapes grow but still hard in texture, high acid/low sugar
Late Summer/Early Autumn - Grapes ripen, sugar rises, acidity drops and flavours develop. Marked by grape colour change; véraison
Later in Autumn - Grapes harvested
What is the difference between Climate and Weather?
Climate - Annual weather pattern over several years
Weather - Variation in a specific year
In hills and mountains, as the altitude increases what happens to temperature?
It decreases
What are the vineyards 4 natural resources?
Temperature, Sunlight, Water, Soil nutrients
Pinot Noir, as a grape variety, is known to randomly change. For example, in the past it has suddenly produced a grey version and was renamed Pinot Gris, a white grape version has appeared and is called Pinot Blanc.
All 3 grapes are related to each other and can be considered what?
Mutations
What is a Cordon?
The arms of a vine made up of 2+ year old wood.
What are the 4 main techniques to manage a vine?
Training, pruning, trellising and planting density
What are day / night temperature changes known as?
Diurnal
What 3 things should a grower consider when selecting a site for a new vineyard?
Environmental - Temp, rainfall, sunlight, soil fertility and drainage. Factors that affect grape selection, planting density and trellising etc.
Business - Proximity to power and water, avail of labour, accessibility for machinery and cost of land.
Grape variety - Must suit climate and meet demand. In EU might be legal restrictions on types used.
What are the 3 main techniques for irrigation?
Drip - Computer controlled dripper for each vine - Expensive
Sprinklers - Also used for frost protection. Waste water and can create damp conditions promoting disease - Cheaper than Drip
Flood Irrigation - Cheapest where water is freely available. Only used on flat or gently sloping vineyards
Briefly explain the effect of
Latitude
Altitude
Ocean Currents
Fog
Soil
Aspect on vine development and grape growing.
Latitude -Usually between 30~50 degrees N and S of the Equator
Altitude - As altitude increases temp drops allowing growth closer to Equator
Ocean Currents - Deliver localised warming/cooling in certain regions
Fog - Can cool an otherwise unsuitable growing area e.g. California, Casablanca Valley, Chile
Soil - Dark soils radiate more heat than lighter. High water retaining soils take longer to warm up
Aspect - Direction slope faces, facing Equator get most heat. Steeper slopes accentuate effect.
What 5 things does a vine need to survive
Heat, Sunlight, Water, Nutrients, Carbon Dioxide
Name 4 vineyards pests and how to control them
Phylloxera- Use resistant rootstock
Nematodes (microscopic worms) - Use resistant rootstock and sanitise soil before re-planting.
Birds and mammals - Birds - Netting / Mammals - Fencing
Insects - Insecticides or Integrated pest management
What is an Inflorescence?
The complete flower head of a plant including stems, stalks, bracts, and flowers
Planting seeds doesn’t work in viticulture, what are the two ways to grow more vines?
a. A cutting (a section of vine shoot is planted and grows)
b. Layering (a section of vine is buried and, in time, takes root)
In regards to temperature, how do Light-colored, Wet and Rocky soils play a part?
- Light coloured soils e.g. Chalk, reflect the suns energy and don’t radiate heat into the vineyard.
- Wet soils, e.g. clay, take longer to warm up and tend to cool the vine
- Rocky soils, e.g. gravel, tend to absorb and radiate heat warming the vineyard.
A Spur is what?
1 year old wood pruned often with 2~3 buds and is quite short.
How is American rootstock resistant to Phylloxera?
They clog the insects mouth with sticky sap and form a protective layer behind the feeding wound to prevent secondary infections
What 3 main reasons can influence planting density?
- Limited water: Low density allows vines to take limited water without competing against the roots of neighbouring vines.
- Low levels of nutrients and sufficient rainfall: Risk is vigorous vegetative growth rather than fruit. High density planting provides competition for resources to limit vegetative growth. Bud management is also important. High density and strict bud control common in Europe.
- High nutrients and sufficient rainfall: High density planting not enough so, instead, low density with vines with multiple cordons or canes.
What is ‘Coulure’ also known as?
What is it?
What is it caused by and how does it affect vines?
AKA “Uneven Set”
Occurs when a significant number of berries do not set after flowering.
Caused by cold weather during flowering or mineral deficiency. Results in reduced yields.
When plants are photosynthesising which of the following equations is correct?
02 + Sunlight + Chlorophyll => Sugars + CO2
C02 + Sunlight + Chlorophyll => Sugars + O2
02 + Heat + Chlorophyll => Sugars + O2
C02 + Sunlight + Veraison => Sugars + O2
C02 + Sunlight + Chlorophyll => Sugars + O2
Which part of the grapes does not contain tannins
Stems
Bloom
Seeds
Skin
Bloom
Name and briefly explain the two common methods of grafting
Bench Grafting - Automated process, both parts joined by machine and stored in warm environment to encourage both parts to fuse together
Head Grafting - Vine is cut back to its trunk and a bud or cutting of the new variety is grafted on to the trunk
What are the four parts of a vine?
Green parts of the vine
One year wood
Permanent wood
The roots
What are the four main forms of frost protection?
Heaters
Wind Machines
Sprinklers
Vineyard design - slopes are less at risk
Describe Continental climate
High Continentality, low rainfall and a very sunny growing season
American vines are rarely used to make wines, what is their main use?
Providing Phylloxera resistant rootstock for Eurasian species to be grafted onto.
What are Tendrils?
The structure the vine uses to support itself by winding themselves tightly around trellis wires to keep the shoot upright
Which statement is NOT true about Permanent Wood?
It is at least 2 years old
It has bark
Cordon is an example of permanent wood
Buds typically burst from permanent wood
Buds typically burst from permanent wood
Identify 2 examples of Continental Climates for the following temperatures:
Cool
Moderate
Warm
Hot
Cool -> Champagne, Mosel
Mod -> Burgundy, Central Otago
Warm -> Ribera Del Duero, Mendoza
Hot -> La Mancha, Douro
How long after new planting is first yield?
Third year after planting
Identify 2 examples of Maritime climates for the following temperatures:
Cool
Moderate
Warm
Cool -> Muscadet, Tasmania
Mod -> Bordeaux, Rias Baixas
Warm -> Auckland, Margaret River
Which statement about Root stock is false?
- Root stocks are used because they are disease resistant
- Root stocks allow the grower to match different Root stocks to different soils
- Changing Root stocks while the plant is growing is called ‘head grafting’
- Root stocks can be used to manage yield
Changing Root stocks while the plant is growing is called ‘head grafting’
What is an untrellised vineyard?
What are the advantages and disadvantages?
Vines not trellised, shoots hang down as far as ground.
Bush vines typically head trained and spur pruned. Best suited to warm/hot, dry, sunny regions (S. Rhone, Barossa Valley), extra shade helps protect grapes. Not suited to cool climates as shade can impede grape ripening and airflow (disease). Not suitable for mechanical harvesting.
Which one of these is the odd one out?
- Grey Rot
- Nematodes
- Powdery Mildew
- Downy Mildew
Nematodes
What are the objectives of Summer pruning?
Trimming the canopy to restrict vegetative growth and direct sugar production to the grape rather than shoots and leaves. Can also involve leaf stripping for max exposure of bunches to sun
Describe a Maritime climate
Low to Medium Continentality, medium to high rainfall all year long & often a cloudy growing season
What is Millerandage also known as?
What are the symptoms?
What is it caused by and what are the results?
Hens and Chicks
Grape clusters with berries that vary in size and number of seeds.
Caused by cold weather at flowering, mineral deficiency, or disease. Results in reduced yields and uneven ripening.
A Cane is what?
1 year old wood pruned leaving with 8~20 buds and is quite long.
Describe the 3 main climate types
Continental - Greatest diff between hottest and coldest months, usually short dry Summers with rapid temp drop in Autumn.e.g. Chablis and Champagne
Maritime - Cool to moderate low annual difference between hottest and coldest months. e.g. Bordeaux
Mediterranean - Low temp diff hottest and coldest months but Summers usually warm and dry e.g. Mediterranean, Coastal Calif, Chile, SA and SE Australia
What is this picture is an example of?
Cordon trained & Spur-pruned vine.
What is Phylloxera?
A tiny aphid that feeds on the roots of vines and is native to the eastern United States.
This picture is an example of what?
Replacement Cane with VSP
A grape vine prefers a mean annual temperature between ____ and ____ with an ideal temperature of ___.
To successfully ripen, red grapes require and average summer temp. of around ____.
To successfully ripen, white grapes require and average summer temp. of around ____.
- between 50° and 68°F, with an ideal of 57°F.
RED: 70°F
WHITE: 66°F.
VSP (Vertical shoot positioning) is a trellising system often used when growing e.g. Chardonnay in a cool climate.
Why would a grower use this system?
In cool climates grapes can struggle to ripen fully. A grower can help the grapes to ripen by increasing exposure to sunlight and heat. In VSP, the shoots are trained up the wires, meaning the grapes are not shaded by any shoots that might otherwise hang down. Their exposure to sunlight and heat is therefore maximised.
When does vine pruning take place?
Every Winter and Summer
What are the pros and cons of Machine and Hand harvesting?
Machine (shakes the trunk)
- Not selective, often collecting unhealthy, unripe and damaged grapes. Can only be used on flat or slight incline vineyards
+ Speed, can work through the (cool) night meaning no need to cool grapes before fermentation.
Hand
- Slower and more Labour Intensive = more expensive
+ Can be used on steep vineyards e.g. Douro, Mosel, N. Rhone. Allows grape selection ‘on the go’, less damage to grapes, stems retained = clean, fresh juice for white and essential for red ‘whole bunch’ winemaking.
What is the objective of Winter pruning?
The main objective is to determine the number and location of buds that will form the shoots in the coming growing season by cutting away unwanted leaves, canes and permanent wood.
Which one of these is associated with manual harvest?
- Can be done at night when temperatures are lower, slowing down oxidation.
- The grapes are shaken violently off the plant
- Low capital costs but higher ongoing costs
- Suitable for all trellising systems
Suitable for all trellising systems
Which statement about buds is false?
They form the year before
They contain immature Inflorescence
They generally only form on shoots at the end of the growing season
The number of bunches each bud produces is dependent upon the amount of sun the bud receives when it is a cane
The number of bunches each bud produces is dependent upon the amount of sun the bud receives when it is a cane
Which of these techniques in NOT used in canopy management
VSP
Trellising
Inter row spacing
Passerillage
Passerillage
What 2 reasons why netting is needed in a vineyard?
To protect the Vine from birds and / or hail
What the Latin name for the most commonly grown vine species?
Vitis Vinifera
Explain ‘Diurnal Range’ and why a large diurnal range can be beneficial to grape-growing:
The diff between daytime and night time temps. Cool nights slow loss of aroma and acidity, warm days accelerate ripening.
What are the 3 main reasons for trellising a vineyard?
i. Arrangement of young shoots controls (maximise/limit) amount of sunlight getting into canopy.
ii. An open canopy can improve air circulation (esp. beneficial in wet climates).
iii. Aids mechanical harvesting and makes spraying insecticides & fungicides more effective.
How can you protect from Hail?
Netting but costly.
Own several vineyards in different locations to mitigate risk
What are the 2 types of Winter pruning?
Briefly summarise each type
Spur and Replacement cane.
Spur - Short sections of 1yr wood, cut down to 2~3 buds.
Replacement cane - Longer sections of 1yr wood with 8~20 buds on, typically 1 or 2 canes
When is it best to do a green harvest?
Shortly after Veraison
In relation to vines, Hybrids are?
Sexual reproduction, with parents being from different vine species
Which soil type has the poorest drainage?
Clay
What can a grower do if yields are potentially going to be too high?
Reduce by removing immature grapes after Véraison. This practice is known as ‘green harvesting’. If done too early vine can compensate by increasing size of retained grapes potentially diluting flavour.
What are Shoots?
This year vine growth
Which statement about Vitis Vinifera is true
- The main Eurasian species for grape production
- It is the preferred species for root stock
- Provides excellent disease resistance
- When harvested green grapes turn blue.
The main Eurasian species for grape production
Cabernet Franc & Sauvignon Blanc got together in Bordeaux to create Cabernet Sauvignon Blanc. This is an example of what?
Crossing
Clones
Hybrids
Mutation
Crossing
Name the Green parts of the Vine
A shoot off which grows; leaves, buds, tendrils and flowers or berries
What treatment is there for Viruses and Bacterial diseases in the vineyard?
There are no treatments or cures. Only solution is to dig up vines and sanitise the land.
What type of climate is this?
Low to medium continentality, medium to high rainfall all year long and often a cloudy growing season
Maritime
What is the objective of Summer pruning?
Trimming the canopy to limit vegatitive growth and direct sugar production to the grapes
Vitis Vinifera fertilised with any other type of V. Vinifera is called what?
Crossing
Vitis Vinifera fertilised with another type of Vitis (not Vinifera) is called what?
A Hybrid
Name 4 temperature hazards
Winter freeze
Frost
Cold temperatures in Spring
Excessive heat
Name 3 water hazards
Drought
Too much
Hail
What are the effects of
Too much nutrients?
Too few nutrients?
Too much = vigorous green growth
To few = Ill health (Chlorosis)
Define vine training
Molding the vines wood and shoots to the required shape
What is a trellis?
Stakes and wires used to support the trained vines
What is the other (French) name for Replacement Cane pruning
Guyot (single or double Guyot)
What happens is there are too few buds left after pruning?
Each bud has access to too much carbohydrate energy and will grow over vigorously
What happens is there are too many buds left after pruning?
Each bud will not have access to enough carbohydrate energy and the vine will struggle to ripen the crop load
Vine density; what density would you use, and why, where there is
Very limited water
Low density planting because the vines won’t have to compete for the limited water
Vine density; what density would you use, and why, where there is
Low nutrients with sufficient water
High density - To provide competition between the vines additionally there should be tight control of the number of buds
Vine density; what density would you use, and why, where there is
High levels of both nutrients and water
Low density planting but with multiple cordons or canes
Name 4 ways to concentrate sugars in grapes in the vineyard:
- Harvesting late.
- Noble Rot (Botrytis)
- Drying grapes.
- Leaving grapes to freeze.
Give 6 examples of regions w/ Rain Shadows:
Alsace / Vosges Mountains
Piemonte / Swiss Alps
Rioja / Cantabrian Mountains
Columbia Valley / Cascade Mountains
Mendoza / Andes
NZ South Island / Southern Alps
How many buds are retained with spur pruning?
2-3
Terroir is defined as:
A French concept that roughly translates to the entire set of factors that influence the development of the vine’s fruit and the characteristics it will show once vinified.
What is a Rain Shadow?
A dry area on one side of a mountain or mountain range, protected from wind, rain and generally poor weather on the opposite side.
What is Green Harvesting and why is it practiced?
- Green Harvesting is a technique employed by farmers whereby grape bunches are dropped or cut off before harvest.
- This is done to reduce yields and focus the vine’s energy/nutrients on fewer, higher quality bunches.
What are 3 positive effects of wind on a vineyard?
Wind can:
- cool/warm a region
- dry a humid region, preventing rot/fungal diseas
- prevent frosts
Name 3 moderators that can help warm a climate:
- Wind can warm a climate if coming from a desert, warm ocean current
- Soil, if stony and gravelly, can retain heat from the sun to keep vines warmer at night.
- Bodies of water, such as lakes, rivers and oceans, cool or warm slower than land, which moderates the temperature of adjacent vineyards.
Desribe the conditions that are necessary for Noble Rot to develop:
Botrytis needs a region with high humidity, misty mornings and dry, sunny afternoons.
Humid mornings encourage rot to develop, hot, dry afternoons allow water to evaporate from perforated grapes.
Botrytis works best on grapes with thin skins (e.g. Semillon/Riesling) that have been allowed to fully ripen.
What 3 roles does a vineyard’s soil perform?
- Influences vineyard temperature.
- Supplies the vine with water.
- Supplies the vine with nutrients.
What is a clone?
A vine that is genetically identical to another, but with observable mutations that result in slight differences, such as better quality fruit or better disease resistance.
Gobelet vines are __pruned and __trained:
Spur-Pruned
Head-Trained
What are the 6 different regions as defined by the California Heat Summation index?
Region Ia 1,500-2,000° days F (850-1,111° days C)
Region Ib 2,000-2,500° days F (1,111-1389° days C)
Region II 2,500-3,000° days F (1,389-1,667° days C)
Region III 3,000-3,500° days F (1,667-1,944° days C)
Region IV 3,500-4,000° days F (1,944-2,222° days C)
Region V 4,000-4,900° days F (2,222-2,700° days C)
What is the vine disease Esca also known as?
Where does it thrive and how is it cured?
How does it harm younger / older vines?
How can it spread?
- Black Measles
- Thrives in warmer climates but exists worldwide, and there is no known control or cure.
- On young vines, the disease will weaken growth, affect berry development and discolor leaves; in hot weather an affected young vine may suddenly die.
- In older vines, the disease affects the wood, causing the interior of the trunk and arms to soften and rot from the inside.
- The disease is exacerbated by rainfall and can be spread by wind or on the pruning shears of careless vineyard workers.
Identify 3 bacterial diseases that can affect grapevines:
Pierce’s Disease
Crown Gall (Black Knot)
Bacterial Blight
How is Pierce’s Disease spread?
How does it harm grapevines?
Where is it commonly found?
What can be done to control it?
- Glassy-winged sharpshooter—a leafhopping insect found near citrus orchards and oleander plants.
- Renders them unable to produce chlorophyll, killing it within 1-5 years.
- Commonly found in Mexico and the Southern US, but it is spreading northwards.
- No known cure, authorities are employing strict quarantine rules to try and contain it.
Which trunk disease is also known as “Dead Arm”?
Eutypa Dieback
How is Eutypa Dieback spread?
Where is it commonly found?
How does it harm grapevines?
Why is it difficult to control?
- Caused by the Eutypa lata fungus. Spores are carried by rain and enter the vine through pruning wounds.
- Common in Mediterranean climates.
- Infected vines experience stunted shoot growth as the fungus releases toxins, and eventually an infected cane may die—the dead arm.
- Difficult to control becuase it afects a wide number of plants/crops.
Which type of vine training is demonstrated in the image below?
Vertical Shoot Positioning
Harvesting in countries in the southern hemisphere will typicall take place between:
February and May
High soil pH is common in what kind of soil?
Are these soils suitable for viticulture?
How do these soils affect the grapes?
What about soils with low pH?
Limestone-rich soils.
Suitable for viticulture, but not other crops.
Contributes higher acidity (low pH) in grapes.
Soil acidity (low pH) can be a deterrent to viticulture.
A Hectare is _____ acres.
2.47
Place the following seasonal events in the life of the vine in proper order (1 = earliest, 5 = latest).
A. Fruit set
B. Véraison
C. Harvest
D. Budbreak
E. Flowering
D. Budbreak
E. Flowering
A. Fruit Set
B. Véraison
C. Harvest
_____ is the father of biodynamics.
Rudolf Steiner
Sélection massale is a ___ selection, in which ___ is taken from ____ in the vineyard, rather than from ______.
field
budwood
a number of vines
a single clone.
Downy Mildew, also called _____, can be successfully controlled through applications of ____.
Peronospera
Bordeaux mixture
In which stage of the vine lifecycle would hail be MOST destructive?
Why?
Flowering.
Vines are especially vulnerable to cold weather.
What is vine “weeping” or “bleeding”?
When does this usually happen (in the northern hemisphere)?
This will occur when the air reaches what average temperature?
When watery sap is excreted from pruned canes sometime in February.
When the average air temperature surpasses 50°F.
Which vine disease is typically spread by soil nematodes?
Fanleaf degeneration
How is Fanleaf Degeneration spread?
How does it affect grapevines?
What are visible symptoms?
What is the only remedy?
Spread by soil nematodes feeding on infected roots.
Deforms shoot growth, and leads to poor fruit set and shot (seedless) berries. The productive lifespan of the vine and its winter durability are diminished.
The leaves on an infected vine are malformed, resembling fans in appearance, and may form yellow bands around the veins.
The infected vines must be removed and the vineyard replanted.
What is Leafroll Virus caused by?
Approximately what % of the world’s grapes might be lost due to the virus?
What are visible symptoms?
How does it affect vines?
How is it cured?
Caused by a complex of at least nine different viruses, spread through propagation of infected vines or by an insect vector like the mealy bug.
May be responsible for as much as 60% of the world’s grape production losses.
Affected vines display radiant shades of red and gold in the autumn and a characteristic downward curling of the leaves.
Reduced yields and delayed ripening.
Currently incurable but it will not kill the vine; thus, infected vines are not always removed.
