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WSET 4 D1 by Sarp Sarac > D1.C8. Hazards, Pests and Diseases > Flashcards

D1.C8. Hazards, Pests and Diseases Flashcards

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1
Q

What are the minimum amounts of water per year needed for the vine in cool climates and warm climates?

A
  • 500 mm per year in cool climates
  • 750 mm per year in warm climates
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2
Q

What can be the results of insufficient water on the vine?

A
  • Closure of stomata
  • Decreased photosynthesis
  • Unripe grapes and lower yields
  • If prolonged, leaf loss and death
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3
Q

What are the management options against drought?

A
  • Irrigation systems (if allowed)
  • Drought resistant rootstocks rootstocks from V. rupestris and V. berlandieri parentage (110R and 140 R
  • Drought tolerant cultivars like Garnacha
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4
Q

What can be the results of excess of water on the vine?

A
  • Too much vegetative growth, shading the fruit, compromising ripeness
  • Increased risk for fungal diseases
  • Waterlogging
    + Reducing the amount of oxygen available to the roots, slowing down growth and eventually killing the vine
    + Compaction of the soils, making them difficult to work, and uncontrolled water run-off
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5
Q

What are the management options against excess of water?

A
  • Drainage systems
  • Planting on slopes
  • Planting on free draining soil
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6
Q

What are the adverse effects of excess rainfall during pollination and fruit set, during summer and close to harvest?

A
  • Pollination and fruit set: Millerandage and coulure
  • Summer: Reduce the rate of ripening of fruit
  • Close to harvest: Swelling of grapes reducing the concentration of must. Splitting of grapes leading to grey rot. It also makes the harvest difficult
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7
Q

What are the management options against untimely rainfall?

A
  • Choice of the site: Climate, slope
  • Condition of the soil
  • Choice of whether or not to grass the land between rows of vines
  • Adequacy of drainage
  • Monitoring weather forecast: Winemakers may have to weigh up the options of early harvest with potentially less-ripe fruit
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8
Q

Under which temperature, the vine can be seriously damaged or even killed?

A

−20°C / −4°F

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9
Q

Which part of the vine is at most risk for winter freeze?

A

Graft (if grafted on a rootstock), followed by canes or cordons

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10
Q

What are the management options against winter freeze?

A
  • Site selection
    + Hillside sites can be up to 5°C / 9°F warmer than the valley floor
    + Vineyards near large or deep bodies of water
    + Vines should be planted where snow settles most thickly, as a deep layer of snow can provide insulation for the vine
  • Choice of varieties: Cabernet Franc, Riesling, V. amurensis
  • Protecting vines
    + Hilling up: Building up soil around the vine graft
    + Burying up: In extreme climates like China, very costly
    + Vines can also be pruned to have several trunks so that those killed in winter can be replaced
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11
Q

Under what condition does the frost occur?

A

Frosts occur when cold air below 0°C / 32°F collects at ground level, freezing water in the vine

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12
Q

Which part of the vine is at most risk for frost?

A

Newly burst buds or young shoots that have a high-water content

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13
Q

What happens if the buds and shoots are killed because of frost?

A

The vine puts out more shoots from secondary buds

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14
Q

What are the two types of frost

A
  • Advective frost: Caused by large volumes of cold air moving in from very cold areas
  • Radiative frost: It occurs on dry clear nights with no wind, when the heat radiated by the ground or plant tissue escapes unhindered into the atmosphere due to the absence of clouds, fog or haze
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15
Q

Why does freezing cold air collect at valley bottoms?

A

Because the cold air is denser than warm air

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16
Q

What are the preventive measures against frost?

A
  • Avoiding frost pockets, choosing hillside sites where cold air can drain away
  • Delaying pruning to postpone budburst into warmer months
  • Choosing late budding varieties like Riesling
  • High training vines
  • Having bare soil rather than a cover crop, which absorbs more heat during the day and radiates this heat during the night
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17
Q

What are the options when frost threatens?

A
  • Water sprinklers (aspersion)
  • Wind machines
  • Oil or propane gas heaters (smudge pots) and wax candles (bougies)
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18
Q

Which of the options against frost is the only method that is effective against advective frost?

A

Water sprinklers

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19
Q

How do the water sprinklers protect against frost?

A

As water freezes around the parts of the plant, it releases latent heat (the temperature at the growing point may rise up to 3-4 °C) , protecting the plant

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20
Q

What are the two important issues to be considered when using water sprinklers against frost?

A
  • Sprinklers should be turned on when the temperature is above freezing around 1°C
  • The system must be kept on until the temperature increases sufficiently to melt the ice coating
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21
Q

When are the wind machines effective?

A

These are effective where there is an inversion layer, a warm zone of air 10 m above the ground (+3–5°C)

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22
Q

When is the investment for wind machines cost effective?

A

If there is a chance of a damaging radiation frost once every five years

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23
Q

What is a similar solution like the wind machines?

A

Using helicopters

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24
Q

When is the use of helicopters cost effective

A

When the risk is severe, but short term

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25
Q

What are the disadvantages of smudge pots and bougies?

A
  • High cost of fuel
  • High cost of labour
  • Low heating efficiency
  • Air pollution
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26
Q

Which parts of the vine are most vulnerable to hail?

A
  • Shoots, leave and canes when they are young
  • Berries during ripening period (damage and prone to botrytis and other diseases)
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27
Q

Name two areas where grape growers suffer from repeated hail storms?

A
  • Mendoza
  • Burgundy
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28
Q

What are the management options for hail?

A
  • Firing rockets into the thunderclouds to seed them with silver iodide to cause rainfall instead of hail
  • Netting
  • Decrease the risk by planting in different spots
  • Consider the additional cost of crop insurance
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29
Q

Why netting is a more appropriate solution in Mendoza, rather than Burgundy?

A

As netting creates some shading, this solution can only be used where there are high sunlight levels

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30
Q

Why are the grapes more vulnerable to sunburn than the leaves?

A

Because, grape transpiration is much more limited, and therefore less effective, than leaf transpiration

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31
Q

Under which condition, the risk of sunburn increases?

A

When the vines are already in a situation of water stress.

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32
Q

What are the effects of sunburn on grape quality?

A
  • Browning of the grape
  • Bitter taste
  • Increased susceptibility to rot
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33
Q

What should be done to sun burnt grapes?

A

They typically need to be removed by sorting, which reduces yields

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34
Q

What are the preventive options for sunburn

A
  • In the Northern Hemisphere, east-west row orientation should be avoided so that grapes on the south side of the row are not subject to day-long sun and, particularly, intense afternoon sunshine
  • Canopy management
  • If a heatwave is forecast, additional irrigation, where allowed, may be applied to reduce water stress and, hence, the chance of sunburn
  • Special agricultural sunscreen spray can be applied
  • Vines can be shaded with a cloth or net
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35
Q

By which mechanism, does the smoke create “smoky” or “ plastic” aromas in the final wine

A
  1. Aroma compounds in smoke can be absorbed by the grapes.
  2. These compounds bind to with sugars and form aroma-less compounds
  3. These compounds then only become aromatic through the fermentation process
  4. The strength of the aroma can increase during the ageing of wine and during bottle ageing as further aroma precursors break down and become aromatic
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36
Q

What are the management options for smoke taint?

A
  • Affected musts can be tested analytically and/or by micro-vinifications to establish the extent of the problem
  • Hand harvesting, gentle or whole bunch pressing, lower fermentation temperatures and reduced maceration times can reduce the uptake of the compounds
  • Flash détente and reverse osmosis can also help, but will not remove the taint completely
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37
Q

How can phylloxera spread?

A
  • Crawling (rare)
  • By humans (mostly)
    + On the roots of young vines
    + In soil
    + On equipment like leaf trimmers and harvesters
    + By irrigation water
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38
Q

What are the symptoms of phylloxera infestation?

A
  • Vines die of drought in patches that increase in size year by year
  • Vine roots are covered with the insects surrounded by yellow eggs
  • Swellings on older roots
  • Pale green leaf galls on the under-surface of the leaves
  • Slow, stunted shoot growth and leaf yellowing appears in around three years, the plant dies after around five years
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39
Q

Which American vine species are most resistant to phylloxera infestation?

A
  • V. riparia
  • V. rupestris
  • V. berlandieri
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40
Q

Why are the American vine species generally are not preferred for wine making?

A

They have undesirable aromas

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41
Q

Why grafting V. vinifera onto the rootstocks of single American species is problematic in Europe?

A

Because these rootstocks have little lime tolerance, resulting in chlorosis

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42
Q

How was the lime intolerance issue solved for American rootstocks?

A

By developing rootstock hybrids

  • 99 Richter (V. berlandieri x V. rupestris)
  • 5BB Kober (V. berlandieri x V. riparia)
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43
Q

What are nematodes?

A

They microscopic worms

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44
Q

What are the mechanisms that nematodes can damage vine?

A
  • Causing damage by feeding off vine roots
  • Transmitting viral diseases (fanleaf virus is transmitted by dagger nematode)
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45
Q

What are the two most common nematodes?

A
  • Root-knot nematode
  • Dagger nematode
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46
Q

How do nematodes spread?

A

Nematodes are either present in the soil already or can be spread by unclean nursery stock, irrigation water or vehicles

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47
Q

What are the management options for nematodes?

A
  • Fumigation of the soil
    + By chemicals: Banned in most regions
    + Plough in a cover crop of mustard plant, that work as biofumigants
  • Using nematode-resistant rootstocks: Ramsey and Dog Ridge (both V. champini)
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48
Q

How do the grape moths damage the vines?

A
  • By feeding on flowers and grapes. They have several generations per season, attacking flowers in spring and grapes later in the year
  • The wounds created are then vulnerable to further attack from bacteria and fungi
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49
Q

What are the most common types of moths in different continents?

A
  • Southern Europe: European grapevine moth
  • Australia: Light brown apple moth
  • Central and eastern North America: Grape berry moth
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50
Q

What are the management options against grape moths?

A
  • Biological controls
    + Bacillus thuringiensis: It produces substances that are toxic to the moths
    + Pheromone capsules: Disrupt mating (sexual confusion)
    + Natural predators: Parasitic wasps, green lacewings, some spider species
  • Insecticides
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51
Q

What are the most destructive spider mites in California and in Europe?

A
  • California: Pacific spider mite
  • Europe: Red spider mite and two forms of yellow spider mite
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52
Q

On which part of the vine do the spider mites feed?

A

They feed on the surface cells of leaves

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53
Q

What are the symptoms of spider mite infestation?

A
  • Discoloration of the leaves
  • Reduction of photosynthesis leading to delayed ripening and reduction in yields
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54
Q

What are the favorable conditions for the spider mites to thrive?

A
  • Dusty conditions
  • Water stressed vines
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55
Q

What are the management options for spider mites?

A
  • Reducing dust by the use of water sprinklers, cover crops or mulches
  • Encourage predatory mites (Tyhplodromus pyri)
  • Specific pesticides that do not kill predatory mites (costly)
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56
Q

How do leafhoppers and ladybugs adversely affect viticulture and vinification?

A
  • Leafhoppers cause direct damage to the leaves
  • Ladybugs can taint wines if they are in amongst the harvested grapes
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57
Q

What kinds of damages can birds create in vineyard

A
  • Direct damage to the berries
  • Damage allows bacteria and fungi to enter bunches, which leads to rot
58
Q

Which birds can attack vineyards?

A
  • Starlings
  • Sparrows
  • Ravens and silvereyes in Australia
59
Q

What are the management options against birds?

A
  • Netting: Justified in high value areas like Mornington Peninsula where birds are a major threat
  • Bird scarers: Scarecrows, models of predatory birds, shiny disks on strings
  • Acoustic: Gas-guns, distress calls, predator noises
  • Predators: Falcons
60
Q

How can mammals damage vineyards?

A
  • Eating shoots
  • Eating grapes
  • Breaking skins of the grapes making them vulnerable to rot
61
Q

What are the common mammal pests for the vineyards?

A
  • Deer
  • Rabbits
  • Kangaroos
  • Racoons
  • Wild boars
  • Baboons
62
Q

What is the management option against mammals?

A

Fencing

63
Q

What should be the properties of fences against mammals?

A

They have to both be sufficiently high and sunk into the soil to stop burrowing animals

64
Q

Name the common fungal diseases affecting vines.

A
  • Powdery mildew
  • Downy mildew
  • Grey rot
  • Eutypa dieback
  • Phomopsis cane and leaf spot
  • Esca
65
Q

What is the cause of powdery mildew?

A

Erysiphe necator (aka Oidium tuckeri)

66
Q

What is the origin of powdery mildew?

A

America. It was introduced to Europe in the middle of the 1800s

67
Q

Name two varieties which are more prone to powdery mildew

A
  • Cabernet Sauvignon
  • Chardonnay
68
Q

In which parts of the vine, does the powdery mildew overwinter?

A
  • Buds
  • Canes
69
Q

To which parts of the vine, does the powdery mildew attack?

A

Young, green parts

70
Q

What are the signs of powdery mildew?

A

Affected parts of the vine show as dull grey patches and become black patches as they advance

71
Q

How can powdery mildew adversely affect viticulture?

A
  • Patches can damage young shoots, inflorescences and grapes, reducing yield
  • Grapes can also split at véraison and become targets for other infections
72
Q

What are the optimum conditions for powdery mildew?

A
  • Shady conditions
  • Temperature around 25°C
73
Q

Why is powdery mildew different than other mildews, when the predisposing conditions are concerned?

A

Unlike other mildews it does not require high humidity and so can spread in relatively dry conditions, especially in dense, shady canopies.

74
Q

What are the management options for powdery mildew?

A
  • Keeping an open canopy
  • Sulphur (both prevents and treats)
  • Systemic fungicides
75
Q

When do the growers apply sulphur against powdery mildew?

A

From a couple of weeks after budburst and up to véraison

76
Q

Why is it important to spray sulphur early in the season?

A

As the disease is easier to prevent than to contain if it gets established

77
Q

What are the advantages of systemic fungicides over sulphur sprays against powdery mildew?

A
  • They can penetrate green tissue of the vine
  • They are not washed off by rain
78
Q

What is the limitation for systemic fungicides?

A

Limited number of applications can be made in one year, otherwise fungus can become resistant

79
Q

What is the cause of Downy mildew (Peronaspora)?

A

Plasmapara viticola

80
Q

Where does Peronspora live?

A

It lives within vine tissue, not on the surface

81
Q

To which parts of the vine, does the Downy mildew attack?

A
  • It attacks green parts of the plant, especially young leaves and flowers, reducing yields by defoliating the vine
  • Grapes can also be affected, but this is less important than the threat of defoliation
82
Q

What are the optimum conditions for Downy mildew?

A
  • Rainfall
  • Warm temperatures (20°C)
83
Q

What are the high-risk periods for Downy mildew?

A
  • Warm springs
  • Stormy but warm summers
84
Q

What are the signs of Downy mildew?

A
  • Yellow, circular ‘oil spots’ and then white, downy fungal growth on the underside of leaves
85
Q

What are the management options for Downy mildew?

A
  • Good drainage and open canopy
  • Bordeaux mixture
  • Fungicides
86
Q

What is “Bordeaux mixture”?

A

It is a combination of copper sulfate and lime

87
Q

What is the advantage Bordeaux mixture?

A

It can be used in organic viticulture

88
Q

What are the disadvantages Bordeaux mixture?

A
  • Protection from these copper sprays only lasts until 20 mm of rain has fallen
  • There are concerns about the build-up of copper in the soil and in water and the EU is looking to reduce and, ultimately, eliminate its use
89
Q

What is the cause of grey rot?

A

Botrytis cinerea

90
Q

How can grey rot adversely affect vines?

A
  • Loss of yield
  • Drop of quality (color, body, aroma/flavour)
91
Q

What conditions make the vine vulnerable to grey rot?

A

Conditions which create points of entry by dmaging the grape skins:

  • Tight bunches
  • Puncture by pests, hail etc
92
Q

What happens if the flowers are affected by grey rot?

A

The fungus can stay dormant in the grape and re-emerge after véraison

93
Q

Which kind of varieties are more prone to grey rot?

A

Varieties with tight bunches or thin skins: Semillon, Sauvignon Blanc, Pinot Noir

94
Q

What are the management options for grey rot?

A
  • Selecting grape varieties that have small grapes with thick skins and therefore high levels of resistance (e.g. Petit Verdot)
  • Protecting the grapes against other pests
  • Open canopy
  • Fungicides
  • Antagonistic bacteria (B. subtilis)
95
Q

What are the key points in the season for spraying against grey rot?

A
  • When the flowering is nearly complete
  • At the end of the grape formation
  • At bunch closure
  • Véraison
96
Q

What is the cause of Eutypa dieback? (E)

A

Eutypa lata

97
Q

How does Eutypa dieback spread?

A

Airborne. Spores are spread by wind over long distances

98
Q

What is the critical climatic factor for the spread of Eutypa dieback?

A

Rain: Spores are shed right after the rain up to 36 hours thereafter

99
Q

How does Eutypa dieback enter vine?

A

Through pruning wounds

100
Q

What are the signs of Eutypa dieback?

A
  • Stunted shoot growth
  • The leaves become yellow, often becoming cupped and tattered around the edges
101
Q

When are the signs of Eutypa dieback most prominent? Why? (E)

A
  • Eutypa dieback is most obvious in spring when shoots are 30 to 70cm long.
  • Because inspections after this timeframe can be more difficult as canopy growth often conceals symptoms, especially in shoots showing mild symptoms
102
Q

When do the foliar symptoms develop after the Eutypa dieback infection? (E)

A

Foliar symptoms usually develop within 3-8 years of infection

103
Q

Name 3 varieties which are susceptible to Eutypa dieback.

A
  • Grenache
  • Cabernet Sauvignon
  • Sauvignon Blanc
104
Q

Eutypa dieback is particularly prevalent in which wine regions of the world?

A
  • Australia
  • South-west France
  • California
105
Q

What are the management options for Eutypa dieback?

A
  • Pruning late and applying fungicides to pruning wounds
  • Affected trunks can be cut back 5–10 cm beyond the visible symptoms and treated with fungicide. Dead wood must be burnt
  • Biological controls (e.g. Bacillus subtilis)
  • Retrain from a sucker or removing the vine and replanting it
106
Q

What is the cause of Phomopsis cane and leaf spot?(E)

A

Phomopsis viticola

107
Q

What are the ideal conditions for Phomopsis cane and leaf spot?

A
  • Cool and wet springs followed by humidity and moderate temperatures
108
Q

What are the signs of Phomopsis cane and leaf spot? (E)

A
  • Leaves
    + Small dark brown spots, usually less than 1 mm in diameter, with 2–3 mm of yellowish halo surrounding the
    brown spot.
    + Spots can become more numerous, but do not grow in size.
    + Leaves can distort as spots darken and drop out.
    + Leaves with badly affected stems can turn yellow and fall
  • Green shoots
    + Small spots with black centres develop, usually on the lower internodes, gradually expanding and elongating to form black crack-like lesions up to 5–6 mm long
    + Large numbers of merging spots on badly infected shoots may give a ‘scabby’ or ‘corky’ appearance. As
    canes grow and harden, the fissures crack and scar
    + Weakened older shoots (30–60 cm long) can break under a heavy crop load or in strong winds
  • Inflorescences: Rare, Phomopsis can cause black speckled rotting of berries, particularly in cool wet conditions. Berry rot rarely occurs without prior leaf and shoot symptoms
  • Lignified canes:
    + Infected canes may be bleached white in winter.
    + Bleached areas, particularly those around the nodes, become speckled with small black spots (the resting
    structures of the fungus)
109
Q

Name one variety that is very susceptible to Phomopsis cane and leaf spot.

A

Grenache

110
Q

What are the management options for Phomopsis cane and leaf spot?

A
  • Fungicides should be applied three weeks after budburst and then every two weeks if wet conditions continue
  • Diseased and dead wood should be removed during pruning and the removed wood (prunings) then burnt or buried
  • Canopy management techniques
111
Q

What is the cause of Esca?

A

It s a complex fungal disease caused by a group of organisms

112
Q

Esca is particularly prominent in which type of climates?

A

Warmer and drier climates like southern Europe and California

113
Q

How does the fungi causing Esca enter the vine?

A

Through the pruning wounds

114
Q

What are the signs of Esca?

A
  • Tiger-striping of the leaves
  • Spotting inside the wood
115
Q

What are the effects of Esca on vines?

A

Esca reduces the yield of the plant and leads to its death within a few years

116
Q

What are the management options for Esca?

A

There is no chemical control, so prevention is important

  • Sourcing disease-free stock
  • Trying new, less detrimental, pruning techniques
  • Not pruning in the rain
  • Removing prunings promptly from the vineyard
  • Disinfecting pruning wounds
  • Research is continuing into using biological agents such as Bacillus subtilis
117
Q

What is the cause of Pierce’s Disease? (E)

A

Xylella fastidiosa bacteria

118
Q

What is the origin of Pierce’s Disease?

A

It originated on the American continent. It initially affected the southern USA and Central America, and is present in California

119
Q

By which mechanism does Pierce’s Disease damage the vine?

A

It lives in the sap channels of vines, which it clogs, leading to grape shrivelling, dropping leaves and the death of the vine between one and five years

120
Q

How is Pierce’s Disease spread?

A

The glassy-winged sharpshooter has led to the disease being spread more rapidly from the 1980s on

121
Q

Name two varieties which are more susceptible to Pierce’s Disease

A
  • Chardonnay
  • Pinot Noir
122
Q

What are the management options for Pierce’s Disease?

A
  • No chemical control
  • Reducing the number of vectors
    + Removing vines close to rivers
    + Chemical insecticides
    + Introducing a species of wasp that feeds on the eggs
    of sharpshooters
  • Strict quarantine rules for the movement of plants
  • Work is being done on developing Pierce’s Disease-resistant vines
123
Q

What is grapevine yellows?

A

It is a generic name for a group of diseases caused by phytoplasmas

124
Q

What are the pathways of spread for grapevine yellows?

A
  • Leafhoppers
125
Q

What is the most common type of grapevine yellows in Europe?

A

Flavescence dorée

126
Q

In which wine regions, is grapevine yellows present?

A
  • Southern France
  • Germany
  • New York State
  • Australia (different form)
127
Q

What are the signs of grapevine yellows?

A
  • Delayed budburst
  • Drooping posture because the new shoots fail to become woody
  • Canopy turning yellow (in white varieties) and red (in black varieties)
  • In some strains, the vine dies as the disease progresses, in others it can recover after an attack
128
Q

What are the most vulnerable varieties against grapevine yellows?

A
  • Chardonnay
  • Riesling
129
Q

What is the economic impact of grapevine yellows?

A

Drastically reduced yields and lower quality (high acidity and low sugar contents of grapes)

130
Q

What are the management options against grapevine yellows?

A
  • There is no control against the bacteria
  • Vector control
    + Insecticides
    + Removal of plants that host hoppers, including cover crops
  • Best practice in the nursery is to bathe the pruning wood in hot water to kill the disease
131
Q

Which group of viruses cause fanleaf degeneration/decline disease? (E)

A

Fanleaf degeneration/decline disease is caused by several different virus species.
Viruses causing fanleaf degeneration/decline are nepoviruses (acronym for ne = nematode-borne; po = polyhedral particle)

132
Q

What is the most widespread nepovirus? (E)

A

Grapevine fanleaf virus (GFLV) is the most well characterized nepovirus, and is by far the most widespread and important cause of the disease worldwide

133
Q

What are the signs of fanleaf degeneration?

A
  • Canes can grow in distorted ways
  • Leaves are very pale, malformed and can look like a fan
134
Q

What are the pathways of spread for fenleaf viruses?

A
  • Dagger nematodes
  • Long distance spread of nepoviruses occurs primarily through movement of infected propagation materials and their subsequent careless use in propagation and grafting
135
Q

Name one variety that is susceptible to fanleaf degeneration

A

Cabernet Sauvignon

136
Q

What are the management options against fanleaf degeneration?

A
  • There is no cure so affected vines will have to be removed and replaced, adding to cost
  • Measures against nematodes
    + Soil fumigation
    + Deep plowing
    + Cover crops with nematicidal properties
    + Lengthy fallow periods (up to 10 years)
    + Use of nematode-tolerant rootstocks
  • Using virus tested clean planting material
137
Q

What is the reason for leafroll?

A

The disease is associated with all species of Grapevine leafroll associated viruses (GRLaV).

138
Q

What are the pathways of spread for leafroll viruses?

A
  • Grafting
  • Mealy bugs
139
Q

In which wine regions, mealy bugs are a key pest?

A
  • South Africa
  • The Mediterranean
  • Argentina
  • Some parts of California
140
Q

What are the signs of leafroll infection?

A
  • The typical downward rolling of the vine’s leaves which usually occurs in autumn
  • The leaves change colour in the autumn to red for black grape varieties and to yellow for white grape varieties
  • Some vines and rootstocks carry the virus without showing symptoms
141
Q

What are the effects of leafroll virus on the vine?

A
  • While the condition does not kill vines, it can reduce yield by up to half and affect quality negatively
  • It slows down the growth of roots and shoots
  • Surviving fruit may take several additional weeks to ripen and have more acidity, less colour and lower sugar levels
142
Q

What are the management options for leafroll virus?

A
  • There is no cure for leafroll virus and therefore the only solution is to remove unproductive vines and replant with virus-free stock
  • Nurseries can screen vines for virus infections
  • Pest control
    + Mealy bugs favour humid environments and therefore open canopies help to reduce the pest
    + Traps
    + Encourage the mealy bug’s natural predators: Ladybugs and lacewings
    + Control by spraying is difficult because of the mealy bug’s waxy coating

WSET 4 D1 by Sarp Sarac (19 decks)

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