Growing Environment Flashcards
What makes up the structure of a grapevine?
Grapevine structure is divided into 4 sections: the shoots, one-year-old wood, permanent wood and the roots
What are the major structures of shoots?
Buds, leaves, tendrils, lateral shoots and inflorescence / grape bunches
Describe a prompt bud
Prompt buds burst within the current growing season producing lateral shoots
Describe a compound bud
Compound buds remain dormant until next spring and provide shoots for the next growing season.
Describe what lateral shoots are
Lateral shoots grow from buds formed in the current year (prompt buds).
They are smaller and thinner than primary shoots. Have a stem, leaves, buds, tendrils and sometimes inflorescences.
Main function is to allow plant to carry on growing if tip of primary shoots are damaged.
In modern viticulture, describe the two way that vines are propagated
Cutting - a section of vine shoot is planted and then grows as a new plant. Permits use of rootstocks, onto which vine cutting can be grafted.
Layering - method of filling in grapes in a vineyard by using shoots from an established neighbouring vine to produce a new vine. A cane is bent down and a section is buried in the ground. Tip if the cane points up out of the ground. The section that is buried takes root.
Describe what a clone is
Methods of cutting and layering usually produce vines that are genetically identical to the parent vine. Cell division during plant growth there is a risk that random mutations in genetic code will occur.
Describe clonal selection
Traditional technique where vineyard owners take cuttings from vines in their own vineyard(s) and cultivate the cuttings.
Cuttings taken from several different vines, usually the best-performing vines selected. These vines are selected after several years of monitoring and recording their performance.
Define photosynthesis
CO2 + sunlight + water = glucose + oxygen
Photosynthesis is a biochemical process that occurs primarily in the leaves of grapevines, where chlorophyll captures heat from sunlight and uses it to transform carbon dioxide from the atmosphere and water from the soil into sugar and oxygen.
Describe transpiration
Transpiration is a process where water is diffused out stomata, which are pores on the underside of leaves. The process draws water and nutrients from the soil, up through the roots and xylem to the leaves and rest of the vine.
What are the requirements of the vine? (inputs and outputs)
Inputs - Carbon dioxide, sunlight, heat, water, nutrients
Outputs - Oxygen
What are the phases of the vine growth cycle?
Green Growth - Dormancy, budburst, flowering & pollination, shoot formation
Grape Development - Grape formation, veraison, ripening, extra-ripening
Describe coulure
Coulure is a condition of grape bunches where fruit set has failed for a high proportion of flowers. It occurs when ovule fertilization is unsuccessful and no grape develops.
It is caused by low rates of photosynthesis and low carb levels caused by cold, cloudy conditions or hot, arid conditions with high water stress.
Describe Millerandage
Millerandage is a condition of grape bunches where there is a high proportion of seedless grapes. It is a result of some of vine’s flowers remaining unpollinated or forming very small berries that have no seeds.
It is caused by cold, wet, windy weather at fruit set.
Describe the climate classifications.
GST = growing season temp
Cool climate - average GST of < 16.5 C
Moderate climate - average GST 16.5 - 18.5 C
Warm climate - average GST 18.5 - 21 C
Hot climate - average GST > 21 C
Describe the Maritime climate category
Maritime - low annual differences between summer and winter temps
Rain spread evening throughout the year.
Example: Bordeaux
Describe the Mediterranean climate category
Mediterranean - low annual difference between summer and winter temps
Annual rainfall tends to fall in winter months, giving dry summers.
Examples - Napa Valley, Coonawarra
Describe the Continental climate category. Give an example.
Continental - more extreme differences between summer and winter temps.
Short summers, cold winters with temps rapidly changing in spring and autumn
Examples - Burgundy, Alsace
Describe Growing Degree Days (GDD)
GDD is a model of heat summation during the growing season that was created by Winkler and Amerine in 1944.
For Celcius, subtract 10 C from average mean temp of a month in the growing season. Multiple that number by the number of days in the month. Do calculation for April - October in Northern Hemisphere and October - April in Southern Hemisphere.
Describe the mean temp of the warmest month (MJT). What else does it measure?
MJT was created by Smart and Dry in 1980. It uses the mean temp of July (Northern Hemisphere) and January (Southern Hemisphere).
MJT - Mean January/July Temperature
Also measure continentality, humidity and hours of sunshine.
Divided into 6 bands - cold to very hot
Describe Growing Season Temperature (GST)
GST uses mean temp of the whole growing season. Closely related with Growing Degree Days (GDD).
Grouped into climatic bands from cool to hot.
List nutrient requirements for vines
Nitrogen, Potassium, Phosphorus, Calcium, Magnesium
List the hazards to vineyards
Freeze, Frosts, Hail, Sunburn, Fire, Smoke Taint, Drought, Excess Water, Untimely Rainfall
Describe the vine cycle phase called Dormancy. Describe vine needs and adverse conditions.
NH - Nov - Mar SH - May - Sept
Vine needs - Temps below 10C
Adverse conditions - Extremely cold temps, unusually mild temps
-20C - vines damaged or killed
-25C - kills most v. vinifera
Winter pruning takes place
Describe the vine cycle phase called Budburst. Describe the vine’s needs and adverse conditions.
NH - Mar - Apr SH - Sept - Oct
Vine needs - Average air and soil temps above 10C
Adverse conditions - Frost, Cold soils
Buds swell, open and green shoots start to emerge. Timing depends on - air temp, soil temp, grape variety, human factors
Describe vine cycle phase called Shoot & Leaf Growth
NH - Mar - Jun SH - Sept - Dec
Vine needs - Stored carbohydrates, warmth, sunlight, nutrients, water
Adverse conditions - Low carbohydrate levels (caused by previous growing season), water stress
Shoots continue to grow leaves and inflorescences mature.
Describe vine cycle phase called Flowering & Fruit Set. Describe what the vine needs and adverse conditions.
NH - May - Jun SH - Nov - Dec
Vine needs - Warm temps ( > 17C), sunlight, warmth, water, nutrients for bud fruitfulness in next growing season
Adverse conditions - rainy, cloudy, windy, cold temps
Flowering - opening of individual flowers within an inflorescence
Fruit Set - flowers pollinate and grapes form
Describe vine cycle phase called Grape Development
NH - Jun - Sept SH - Dec - Mar
Vine needs - Sunlight, warmth, mild water stress
Adverse Conditions - Too much water and nutrients, excessive shading of grapes, very cold or very hot conditions throughout day and night
Describe the early grape growth stage which is part of the Grape Development vine cycle phase
Earth grape growth starts soon after fruit set. Hard green grapes start to grow in size and tartaric and malic acids accumulate.
Some aroma compounds / precursors (methoxypyrazines) develop.
Tannins accumulate, but are very bitter.
Sugar levels are low.
Describe the veraison stage which is part of the Grape Development vine cycle phase
Grape growth slows down for a few days, called lag phase. Grape cell walls become stretchy and supple, green-coloured chlorophyll in skin cells is broken down.
Grapes of black varieties become red in colour due to the synthesis of anthocyanins
Describe the ripening stage which is part of the Grape Development vine cycle phase
Most important process in determining final grape quality.
Shoot growth slows down. Cells in grapes expand rapidly, sugar and water accumulate and acid levels fall. Tannins, colour and aroma precursors / compounds develop.
Harvest marks the end of this stage.
Describe the extra-ripening stage which is part of the Grape Development vine cycle phase
If grapes left on the vine, they start to shrivel. No more sugar or water important into grape. Water loss through grape transpiration means sugars become concentrated.
Extra-ripe aromas develop.
List the influences on regional and site climate
Latitude, Altitude, Mountains, Slopes/Aspect, Soil, Water, Air
Describe how latitude affects temperature and sunlight
Lower latitude (near Equator) receive more solar radiation than regions at higher latitudes (nearer the Poles)
Regions near Equator receive more intense solar radiation than nearer poles. Solar radiation is absorbed and scattered as it travels through Earth’s atmosphere, decreasing its intensity.
Lower latitudes - temps are warmer, sunshine more intense - grapes have higher sugar, lower acidity
Describe how altitude affects temperature and sunlight
Temp falls by approx. 0.6 C for every 100 m increase in altitude.
High altitude sites can be favourable in areas of low latitude that would be too hot.
Sunshine more intense at high altitudes - solar radiation travels through less atmosphere.
High altitude has high diurnal range (difference between day and night temps). In warm climates, high diurnal range can be beneficial for retention of avidity during grape ripening.
Describe how mountains affect water availability
Mountain ranges can force winds of warm most air upwards over high altitudes. This causes water vapour to cool, condense and precipitate.
Regions on one side of mountain experience greater rainfall, while regions on the other side are sheltered from rain-bearing winds and often have very dry conditions.
Describe aspect and how it affects temperature and sunlight
Aspect - vineyards planted on slopes face a certain direction. Important characteristic of vineyard site, especially in cool climates.
Vineyards that face the sun through most of the day receive more solar radiation than those facing opposite direction.
Importance of aspect and steepness of slope increases at high latitudes because solar radiation hits Earth at a low angle at high latitudes
Describe slope and how it affects temperature and sunlight
Slope - or incline, an important characteristic of any vineyard site that isn’t completely flat.
Slopes increase the angle at which solar radiation hits Earth’s surface, increasing the intensity of heat and light.
Slopes facing east benefit from morning sun - heat up atmosphere when air and soil are lowest. Can extend hours of vine growth and grape ripening each day, especially in cool climates.
Slopes facing west receive afternoon sun and may become too hot (warm climates) and there is a risk of sunburn.
Describe how proximity to water affects temperature and sunlight
Large bodies of water have significant impact on nearby vineyards. Water heats up and cools down more slowly than dry land.
During the day, the water and air above the body of water remains cool and lowers average temp in local area.
Air above dry land heats up more quickly than that above water - this warm air rises.
Opposite happens at night - water retains warmth gained during the day, whereas, without solar radiation, the land loses heat quickly. Warmth of water keeps the local area warmer.
Describe how winds affects temperature and sunlight
Winds and breezes have a warming or cooling influence on wine regions. Areas near bodies of water may experience cool breezes during the day, moderating diurnal range of regions.
Valleys that face the coast can mean winds are felt far inland. Valleys can lead to stronger winds as moving air is funnelled.
Winds that have travelled over hot land masses can bring warm air that heats the vineyard area.
Describe how the characteristics of soil affects temperature and sunlight
Soil can have an effect on temp. Drainage of soil, its texture and colour all influence warmth of soil and air directly above it.
Soil that drain freely (stony, sandy) warm up more quickly in spring than damp soils. Rising soil temp encourages breakdown of starch in roots, which stimulates budburst and shoot growth.
Desirable for cool-climate areas to have free-draining soils to promote early budburst and potentially longer growing season to help grapes ripen
Light coloured soil reflect some energy from solar radiation. Useful in cool and cloudy climates because extra light energy reflects into lower parts of canopy that receives less sunlight. Dark coloured soils absorb more energy and re-radiate most of it when temps are cooler at night. Useful in cool climates.
Describe how mist, fog and clouds affect temperature and sunlight
Depending on density of fog/mist or amount of cloud cover, sunlight can be limited and photosynthesis reduced.
With less solar radiation, temps can be lower, especially if morning fog or cloud delays time at which morning sun begins to warm the land.
Where mist/fog is common, it can slow down sugar accumulation and acid degradation in grapes, which may be beneficial in warm regions or when growing early-ripening varieties.
Mist/fog made up from water droplets that occur at ground level, can increase humidity in the vineyard, which can increase occurrence of fungal diseases, or in areas with dry, sunny afternoons, noble rot.
Describe how rainfall affects water availability
Rainfall is a natural source of water for vines - amount and timing is important in producing high quality grapes. Moderated by water-holding capacity and depth of soil.
Warm temps cause moisture from land to evaporate. As warm moist air rises in atmosphere, it cools and condenses into clouds and eventually rain.
In areas where there isn’t sufficient rain, irrigation may be needed.
Topography can influence rain patterns. Mountain ranges force winds of warm moist air upwards causing rain. Regions on one side of mountain experience greater rainfall; regions on other side are sheltered and often have dry conditions.
Describe how characteristics of the soil and land affects water availability
Amount of water available to vine depends on how easily water drains, the water-holding properties and soil depth.
Hawke’s Bay receives 1000 mm rain annually, but has extremely free draining gravel soils, so irrigation often required.
Jerez, Spain - receives 650 mm ran in winter with virtually no rain in summer months. Main soil type is albariza, which is a clay soil with good water retention and releases water slowly to vines.
Waterlogged soils are harmful to vine - reduces oxygen available to roots and can kill the vine.
Greater surface run-off in vineyards on slopes - less penetration of water available to vine roots - may be advantageous in regions with high rainfall.
Describe what evapotranspiration rate is
Evapotranspiration rate is the amount of transpiration from the vine, combined with the evaporation of water from soil surfaces. It is the rate at which water is no longer available to the vine, that is either taken up by the vine or because it is lost to the atmosphere.
It depends on temp, humidity and wind. Hot, dry, windy weather leads to faster rates of evapotranspiration. This means more water is needed to satisfy needs of the vine. Vines in hot, dry, windy conditions need more water than vines in cool and humid conditions.
Explain why Nitrogen is an important nutrient for grape vines and symptoms of a deficiency
Nitrogen is essential for vine growth. It can have a major impact on vine vigour and grape quality. It is a component of proteins and chlorophyll and required for Photosynthesis.
Too much nitrogen in soil causes excessive vegetative growth, with sugars diverted to growing shoots and leaves rather than grapes, hindering ripening.
A nitrogen deficiency results in reduced vigour and yellowing of vine leaves.
Explain why Potassium is an important nutrient for grape vines and symptoms of a deficiency
Potassium is essential for vine growth and helps regulate the flow of water in the vine. High potassium in soils can cause problems with uptake of magnesium, which can lead to reduced yields and poor ripening.
High potassium in soil leads to high potassium in grapes, which has significant effect on wine quality, as it is linked to high pH.
Low levels of potassium can lead to low sugar accumulation in grapes, reduced yields and poor vine growth.
Explain why Phosphorus is an important nutrient for grape vines and symptoms of a deficiency
Phosphorus is important for photosynthesis. Vines only need a small amount and there is usually enough present in soil.
A deficiency leads to poorly developed root systems causing a diminished ability to take up water and nutrients, reduced vine growth and lower yields.
Explain why Calcium is an important nutrient for grape vines and symptoms of a deficiency
Calcium has an important role in structure of plant cells and photosynthesis. Deficiency is rare but can have negative influence on fruit set.
Explain why Magnesium is an important nutrient for grape vines and symptoms of a deficiency
Magnesium is found in chlorophyll and has a key role in photosynthesis. Deficiency can result in reduced grape yields and poor ripening.
Describe what chlorosis is
Chlorosis is a condition where leaves turn yellow and photosynthesis stops. Grape ripening and yields are negatively affected.
It is caused by iron poorly available in soils with high pH (soils with high proportion of calcium carbonate such as limestone)
Describe what organic nutrient compounds are
Organic nutrient compounds found in and added to soils are not available in a form that vines can take up and needs to be converted into inorganic compounds.
Organic describes compounds that contain carbon.
Organisms that live in the soil (bacteria, fungi, earthworms) are important in this process, feeding on organic matter and converting it into available inorganic forms. These organisms can also convert organic matter into humus.
Describe what the mineralization process is
Organisms that live in the soil (bacteria, fungi, earthworms) are important in this process, feeding on organic matter and converting it into available inorganic forms.
Describe what weather is
A region’s weather is the annual variation that happens relative to the climatic average. Some regions experience greater variation in this pattern than others.
Weather can have a significant influence on the style and quality of wines produced in that year and is often termed vintage variation.
Describe what climate change is
The main measurable effect of climate change is a rise in temperatures. It has the consequent effect of greater evapotranspiration and likelihood of water stress. Other effects include changes in geographical distribution of rainfall, greater weather variability and greater frequency of extreme weather events
Describe the management options for drought conditions
Where allowed, irrigation systems should be considered as part of initial design of the vineyard.
If new vineyard being planted, drought-resistance should be high on list of priorities in choosing a rootstock. Rootstocks from V. rupestris and V. berlandieri parentage (110R and 140R) .
Choose drought tolerant grape varieties such as Garnacha
Describe the management options for excess of water conditions
If excess rain happens on a regular basis, planning of vineyard must ensure the issue is addressed. Where possible, plant on a slope or on free-draining soils to improve drainage. Or a drainage system can be constructed at the time that the vineyard is established.
Describe the management options for untimely rainfall in the vineyard
Nothing can be done about the incidence of rain. Choice of site (climate, slope), condition of soil, choice of whether or not to grass land between rows of vines and adequacy of drainage can mitigate some effects of untimely rainfall.
Monitor weather forecasts. If forecast for heavy rain, winemakers may have to decide to harvest early with potentially less-ripe fruit or taking a chance on weather improving in time for successful harvest later or risk losing part or all of the crop.
What temperatures can a vine be damaged or killed by winter freeze
Temps below -20C can damage or kill a vine by winter freeze
List the high level management options for freeze in the vineyard
Site Selection - hillside sites, vineyards near large or deep bodies of water, vines planted where snow settles most thickly, as deep layer of snow can provide insulation for vine
Choice of Varieties - choose grapes resilient against winter freeze - Cab Franc, Riesling, American and Mongolian vine species and their hybrids
Protecting vines - build up soil around vine graft, bury vines, vines pruned to have several trunks as those killed in winter can be replaced
Describe the 2 types of frost
Advective frosts - caused by large volumes of cold air moving in from very cold areas
Radiative frosts - result of heat being lost on still, cool nights. Earth heated by sun during the day and releases it during the night. Amount of heat lost depends on cloud cover. Windless nights will allow a layer of freezing cold air to develop just above the surface of the soil.
List the management options to reduce the risk of frost in the vineyard
Site selection - avoid frost pockets, choose hillside sites where cold air can drain away
Delay pruning postpones budburst into warmer months.
Choose late-budding varieties - Riesling
Vines trained high off ground offers more protection.
Have bare soil between vines - absorbs more heat during the day and radiates heat during the night
List management options when frost does threaten in the vineyard
Water sprinklers (aspersion) - water freezes around parts of vine and it releases latent heat, which protects the plant
Wind machines - large fans, 4-7 m high, pull warmer air from above ground level to ground level and raises the temp
Oil/propaine gas burning heaters (smudge pots) and wax candles (bougies) can be placed in vineyard and lit. High cost of fuel and labour, low heating efficiency and contribution to pollution
List management options when hail threatens the vineyard
Rockets fired into thunderclouds, seeding them with silver iodide to cause rainfall rather than hail.
Net the fruit zone to protect ripening grapes. Nets create some shading and can only be used in areas with high sunlight - Argentina
Hail damage is selective. In high risk areas growers may seek to have a number of plots in different areas to ensure continuity of production.
Growers have to consider additional cost of crop insurance against hail.
List management options in prolonged hot weather to prevent sunburn to grapes
When designing new vineyards, row orientation and aspect can reduce impact of hottest afternoon sun. In hot regions in NH, east-west row orientation should be avoided so grapes on south side of row are not subject to intense afternoon sun.
Leverage canopy management techniques. Growers can choose to partially shade the fruit zone in hot regions.
Apply additional irrigation if heatwave forecast. Can reduce water stress and chance of sunburn.
Special agricultural sunscreen spray can be applied or vines can be shaded with a cloth or net.
List management options for fires that affect vineyards
Install fire detectors and sprinklers
Install and maintain water tanks
Provide employee training for action in event of emergency
List management options of vineyards are affected by smoke taint
Affected musts can be tested analytically in days leading up to harvest.
Some aroma precursors are present in grape skins, so grapes should be handled gently or use whole bunch pressing, lower fermentation temps and reduced maceration times to reduce uptake of compounds.
Winemakers may be able to rescue affected wines by combination of these measures and by blending with unaffected wines.
List the pests that can harm grape vines
Phylloxera, nematodes, grape moths, spider mites, birds, mammels
Describe how phylloxera spreads and harm vines
Phylloxera is an aphid-like insect that feeds and lays eggs on roots of grapevines. The insects spread through crawling, but most commonly transported by humans on roots of young vines, in soil, on equipment and by irrigation water.
Phylloxera harms vines by damaging roots, reducing uptake of nutrients and water. Damaged roots are vulnerable to additional attacks by bacteria and fungi. These attacks lead to a weakening of the plant (reduced growth, yield) and then to death of the vine.
Describe the management options that can prevent the spread of phylloxera
Use of American vine species (V. berlandieri, V. riparia, V. rupetris). Graft European varieties onto rootstocks from American vines.
Use rootstocks derived from American species that can deal with other problems - nematodes, extremes of soil pH, water stress, salinity and control vigour of the vine.
Today grape growers get professional advice on choice of rootstock and grape variety to match appropriate rootstock to vineyard soil, pests to be combatted and level of vigour desired.
Describe how Nematodes spread and damage grape vines
Nematodes are microscopic worms common in soils, that are too small to see with the naked eye. To most common are root-knot and dagger nematodes.
They cause damage by feeding off vine roots, reducing yields and vigour. They cause a slow, gradual decline.
Nematodes are either present in the soil already or spread by unclean nursery stock, irrigation water or vehicles. Once they are present, they can only be managed, not eliminated.
Describe the management options for Nematodes
Soil samples taken and analyzed in a lab to determine number and type of nematodes present.
Fumigate the soil, but chemicals are banned now.
Plough in a cover crop of mustard plant - contains compounds that work as biofumigants, killing nematodes.
Best solution is to use nematode-resistant rootstocks and ensuring plants bought from nurseries have been heat-treated to kill nematodes. Ramsey and Dog Ridge (V. Champini) are examples of nematode-resistant rootstocks.
Describe how grape moths and how they damage grape vines
Different grape moths - Light brown apple moth (Australia), European grapevine moth (Southern Europe), Grape berry moth (central and eastern North America)
They feed on flowers and grapes. They have several generations per season, attacking flowers in spring and grapes later in season.
Wounds created are vulnerable to further attach from bacteria and fungi, including botrytis and significant crop losses
Describe the management options for grape moths
Biological controls used include bacterium bacillus thuringiensis, which produces substances toxic to moths.
Use of pheromone capsules to disrupt mating and cause sexual confusion. Insecticides can also be used.
Natural predators can be used like parasitic wasps, green lacewings and some spider species.
Describe how spider mites spread and how they damage grape vines
Several different species from region to region. Pacific spider mite (California), Red spider mite and 2 forms of yellow spider mites (Europe)
They feed on surface of cell leaves, leading to discolouration of leaves, a reduction in photosynthesis, delayed ripening and reduction in yields. They thrive in dusty conditions and must damaging when vines are already water stressed.
Describe the management options against spider mites
Make environment inhospitable by use of water sprinklers and/or cover crops or mulches to reduce dust.
Encourage predatory mites (plant host species) that feed on spider mites.
General pesticides may kill mites. Specific sprays can be applied to kill only mites problematic in vineyard, but can add a cost
Describe the damage that birds and mammals can make in the vineyard
Mammals damage vineyards by eating shoots, grapes and leaves, by breaking skins of grapes making them vulnerable to rot.
Describe the management options against birds and mammals
Netting, bird scarers or noises (noises rotated regularly) and falcons can be used to manage birds.
Mammals can be kept out by fencing, but it has to be high and sunk into the soil to stop burrowing animals.
Name the fungal diseases that affect grapes vines
Powdery Mildew, Downy Mildew, Grey Rot, Eutypa Dieback, Phomopsis Cane and Leaf Spot, Esca
Name the bacterial diseases that affect grape vines
Pierce’s Disease, Grapevine Yellows
Name the viruses that affect grape vines
Fanleaf Virus, Leafroll Virus
Describe the fungal disease powdery mildew
Caused by fungus Erysiphe or called oidium tukeri. It overwinters in buds and on canes. It attacks young, green parts of the vine.
Affected parts of the vine show as dull grey patches that become black patches. The patches damage young shoots, inflorescences and grapes and reduces yields
Grapes can split at veraison and become targets for other infections.
Optimum temp is 25C and it thrives in shady conditions. It doesn’t require high humidity and can spread in dry conditions, especially dense, shady canopies
Describe the management options for powdery mildew
Preferred approach is to keep an open canopy to reduce shade and density of leaves.
Application of sulfur helps prevent and treat the disease. Spray a few weeks after budburst and up to veraison. Important to spray early in season as it is easier to prevent than it is to contain once established.
Systemic fungicides can be effective - they penetrate green tissue of the vine and not washed off by rain. Fungus can become resistant to some fungicides, so only limited applications in a year
Describe the fungal disease Downy Mildew
Caused by Peronospora, a water mould that lives in vine tissue, not on the surface. It attacks green parts of the plant, especially young leaves and flowers, reducing yields by defoliating the vine. Grapes can be affected, but less important than the threat of defoliation.
It needs rainfall and warm temps (20C) to spread. High-risk periods are warm springs and stormy but warm summers.
Symptoms are yellow, circular ‘oil spots’ and then white, downy fungal growth on underside of leaves
Describe the management options for Downy Mildew
Spray made of copper salts used to prevent spread, but only lasts until 20 mm of rain has fallen. Bordeaux mixture (combo of copper sulfate and lime) became standard treatment in 1880s. Concerns about build-up of copper in soil - EU looking to reduce and ultimately eliminate its use.
Other fungicides can be used. Good drainage and open canopy that dries quickly are helpful to avoid the fungus from developing and spreading.
Describe the fungal disease grey rot and how it effects grape vines
Fungus is called botrytis cinerea that causes significant damage to fruit resulting in loss of yield and drop of quality in wine.
Grapes vulnerable if any entry points (grapes rubbing together in tight bunches) leading to whole bunches being attacked.
If flowers affected, fungus can stay dormant in grape and re-emerge after veraison. Spores typically present in vineyard and become active in periods of rainfall and high humidity.
Describe the management options for grey rot
Select varieties with small grapes, thick skins and high levels of resistance; protect grapes against other pests that can split skin.
Keep an open canopy and remove leaves around bunches can reduce spread of grey rot
Traditional sulfur and copper sprays are ineffective; other fungicides can be used. Apply fungicides at key points in season - flowering nearly complete, end of grape formation, bunch closure and veraison. Fungicides become quickly ineffective if fungus develops resistance.
Attention turning to using antagonistic bacteria like bacillus subtilis and other forms of biological control
Describe the fungal disease eutypa dieback and how it effects grape vines
Also called dead arm, Eutypa Dieback is a fungal trunk disease that leads to rotten wood in vines that can affect the whole vineyard. Reduces yield and kills vines over 10-year period
Spores spread by wind over long distances. Infection occurs through pruning wounds in moderate temps, especially during rain.
Effects evident in spring with affected vines displaying stunted shoot growth and yellow leaves.
Widespread in South Australia, south-west France and parts of California.
Describe the management options for fungal disease Eutypa dieback
Difficult to control, but pruning late and applying fungicides to pruning wounds can be effective.
Affected trunks can be cut back 5-10 cm beyond visible symptoms and treated with fungicides. Dead wood must be burnt to avoid spores spreading.
Some biological controls (Bacillus subtilis) may be effective.
If plant badly affected, can retrain from a sucker (shoot that grows from base of vine) left on trunk (causes loss of yield for 2 years) or removing the vine and replanting it.
Describe the fungal disease phomopsis cane and leaf spot and how it effects grape vines
Phomopsis is a fungal disease that causes a reduction in yield. Prevalent in years with cool/wet springs followed by humidity and moderate temps.
Infected canes whiten and break off easily; shoots growing from these canes develop brown cracks at their base. Leaves also affected.
Describe the management options for phomopsis cane and leaf spot
Fungicides should be applied every 3 weeks after budburst and then every 2 weeks if wet conditions persist.
Diseased and dead wood should be removed during pruning and removed wood then burnt or buried.
Canopy management to improve air flow with canopy may reduce risk of disease.
Describe the fungal disease Esca and how it effects grape vines
Esca is a complex fungal disease caused by a group of organisms prevalent in warmer/drier climates (southern Europe, California)
It enters through pruning wounds. Symptoms include tiger-striping of leaves and spotting inside the wood.
Describe the management options for Esca
No chemical controls. Pay attention to prevention. Sourcing disease-free stock, trying new, less detrimental pruning techniques, not pruning in the rain, removing prunings promptly from vineyard and disinfecting pruning wounds.
Research continues into using biological agents such as Bacillus subtilis.
Describe the bacterial disease Pierce’s Disease and how it effects grape vines
Pierce’s Disease is a bacterial disease that quickly kills vines. Bacterium lives in sap channels of vines, which it clogs, leading to grape shrivelling, dropping leaves and death of the vine in 1-5 years.
Symptoms are unclear and vines must be tested in a lab.
Spread by sharpshooter insect, which acts as a vector (Glassy-winged sharpshooter)
Describe the management options for Pierce’s Disease
No chemical control. Control by reducing the number of the vector. Remove vines close to rivers is effective as riverbanks can be habitat for vectors (blue-green sharpshooter)
Some chemical insecticides can be used. Introduce species of wasp that feeds on eggs of sharpshooters is effective.
Strict quarantine rules for movement of plants. Future work is being done to develop Pierce’s Disease-resistant vines
Describe the bacterial disease Grapevine Yellows and how it effects grape vines
Group of bacterial diseases with no treatment. Spread by vectors (leafhoppers) and by nurseries selling untreated, diseased stock.
Symptoms include delayed budburst, drooping posture because new shoots fail to become woody, and canopy turning yellow (in white varieties) and red (in black varieties)
In some strains the vine dies as disease progresses, in others it can recover from an attack. Bacteria can live in a range of plants, including cover crops in vineyard.
Describe the management options for bacterial disease Grapevine Yellows
There is no control against the bacteria.
Focus on controlling the vector. Leafhopper populations can be reduced by insecticides, and plants that host the hoppers, including cover crops, should be removed.
Best practice in nursery is to bathe pruning wood in hot water to kill the disease.
Describe the viral disease fanleaf virus and how it effects grape vines
Fanleaf virus (fanleaf degeneration) is a group of viruses now found around the world. Early shoot growth is stunted, canes can grow in distorted ways and leaves are very pale, malformed and can look like a fan.
Effects vary widely from little effect to losing most of the crop in susceptible varieties like Cabernet Sauvignon.
Disease spread by moving grafted vines following phylloxera and inadvertent use of infected plant material. Otherwise, disease is spread slowly by dagger nematode.
Describe the management options for fanleaf virus
There is no cure for fanleaf virus. Eventually, affected vines will have to be removed and replaced.
Before vineyards are replanted, soil tests should be done to check for presence of dagger nematodes and only virus-tested, clean planting material should be used.
Describe the viral disease leafroll virus and how it effects grape vines
Leafroll virus is a group of viral diseases widely present in the world. It is spread by grafting and by mealy bugs, a key pest in South Africa, the Mediterranean, Argentina and some parts of California.
Condition does not kill vines. It can reduce yields by up to half and affect quality negatively. It slows down growth of roots and shoots.
Surviving fruit may take several additional weeks to ripen and have more acidity, less colour and lower sugar levels. Overall health of vine affected as it stores less carbohydrates.
Downward rolling of vine’s leaves occurs in autumn. Leaves change colour in autumn to red for black grapes and yellow for white grapes. Symptoms not always clear, so vines have to be tested in a lab.
Some vines and rootstocks carry the virus without showing symptoms.
Describe the management options for fanleaf virus
There isn’t a cure for fanleaf virus. The only solution is to remove the unproductive vines and replant with virus-free stock. Nurseries can screen vines for infection.
Mealy bugs like humid environments, so open canopies help reduce the pest. Control by spraying is difficult because mealy bug’s waxy coating. Steps can be taken to encourage mealy bug’s natural predators: ladybugs, lacewings and others
