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WSET® Level 4 Wine > WSET® Level 4 D1 Wine Production > D1 Hazards, Pests, and Diseases > Flashcards

D1 Hazards, Pests, and Diseases Flashcards

Major environmental hazards, pests, and diseases that threaten grapevines.

1
Q

What are the leading environmental hazards that can affect vineyards and grapes?

A
  1. Drought;
  2. Excess of water;
  3. Untimely rainfall;
  4. Frosts;
  5. Freeze;
  6. Hail;
  7. Fire;
  8. Smoke taint;
  9. Sunburn.
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2
Q

What are options a grape grower can exercise when trying to manage drought?

A
  1. Consider irrigation as part of the initial design of a vineyard (where irrigation is permitted);
  2. Choose drought-resistant rootstock, e.g. V. rupestris and V. berlandieri parentage (e.g. 110R and 140R);
  3. Choose a drought-tolerant variety, e.g. Garnacha.
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3
Q

What are the potential consequences of a vine having access to excess water, such as too much rainfall?

A
  1. Excess water means robust vegetative growth, which can lead to delayed or less ripening in grapes;
    • canopy competes with grapes for sugars;
    • fruit is too shaded, thereby reducing production of anthocyanins and tannins, and overproduction of methoxypyrazines;
  2. Canopy prone to fungal diseases because of high humidity;
  3. Waterlogging if soils not free-draining;
    • reduces the amount of oxygen available to the roots, which slows growth and eventually kills the vine;
    • can lead to compaction of the soils, making them difficult to work and uncontrolled water run-off.
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4
Q

How can grape growers manage excess water in their vineyard?

A
  • If in the planning stage, plant on a slope or on free-draining soil;
  • Constructing a drainage system.
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5
Q

Describe the potential consequences of untimely rainfall at pollination, mid-season, and right before harvest.

A

At pollination: millerandage or coulure (eventual reduction in crop size and possibly quality);

At mid-season: slowed ripening;

Right before harvest: grapes bloat and sugars dilute; grapes can split, leading to grey rot.

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6
Q

What parts of the vine are most at risk of being damaged by freeze?

A

The graft (if the vine is grafted), followed by canes or cordons.

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7
Q

Name three freeze management options for grape growers.

A
  1. Site selection;
    • hillsides, proximity to water, or where snow settles most thickly;
  2. Choice of grape varieties;
    • resilient varieties will be more hardy;
  3. Vine protections;
    • hilling up, burying vines, pruning several trunks to remove the dead ones killed in winter.
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8
Q

What are the two types of frost?

A
  1. Advective frosts;
  2. Radiative frosts.
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9
Q

What are advective frosts?

A

They are caused by large volumes of cold air moving in from very cold areas.

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10
Q

What are radiative frosts?

A

Result from heat being lost on still, cool nights.

  • Soil is heated up by the sun during the day and releases that accumulated heat overnight; the amount of heat lost depends on the level of cloud cover;
  • Windless nights allow a layer of freezing cold air to form just above the surface of the soil. As cold air is denser than warm air, this freezing cold air will collect on valley floors.
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11
Q

What are some ways a grape grower can reduce risk of frost?

A
  1. Avoid planting in frost pockets;
  2. Choose hillside sites so cold air can drain away;
  3. Delay pruning, which postpones budburst;
  4. Choosing a late-budding variety;
  5. Train vines high off the ground (coldest air is near the ground);
  6. Having bare soil between the vines (soils absorb more heat during the day and radiate this heat during the night).
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12
Q

What are four ways a grape grower can combat a sudden threat of frost?

A
  1. Aspersion;
  2. Wind machines;
  3. Smudge pots;
  4. Wax candles (bougies).
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13
Q

How does hail damage a vine?

A
  1. Perforate or knock off young shoots and leaves;
  2. Grapes skins can tear, inviting disease;
  3. Yield reduction in that vintage (knocking off clusters) and in next year’s yield.
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14
Q

What are some strategies grape growers can employ for hail protection?

A
  1. Firing rockets into thunderclouds, seeding them with silver iodide to cause rainfall rather than hail;
  2. Net the fruit zone to protect ripening grapes;
  3. Have a number of plots in different areas (low risk of hail);
  4. Crop insurance against hail.
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15
Q

How do grapes become sunburnt?

A

Grape transpiration is more limited and less effective than leaf transpiration, so in prolonged hot weather grapes can reach higher temperatures than the leaves leading to sunburn.

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16
Q

What are the effects of sunburn on grapes?

A
  1. Scars on the grape skins and possible eventual death of the grapes;
  2. Negative impact on overall grape quality;
    • browning of the grape, a bitter taste, and increased susceptibility to rot (due to skin damage);
  3. Yield reduction, as sunburnt grapes must be removed at the sorting table.
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17
Q

What are some options for grape growers to manage sunburn?

A
  1. Proper row orientation and aspect consideration for new vineyards will reduce impact of hottest afternoon sun;
  2. Canopy management techniques;
  3. Additional irrigation to reduce water stress (if irrigation allowed);
  4. Special agricultural sunscreen spray;
  5. Shading vines with a cloth or net.
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18
Q

How do grape growers prepare their property in areas that are prone to fires?

A
  • Install fire detectors and sprinklers;
  • Install and maintain a water tank;
  • Provide employee training for action in the event of an emergency.
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19
Q

When are grapes most susceptible to smoke taint?

A

From véraison onwards

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20
Q

Aroma compounds from smoke taint only become aromatic through the ____ process, and become more pronounced during the ____ process.

A

Fermentation

Bottle aging

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21
Q

How do grape growers manage smoke taint?

A
  1. Analyze affected musts and/or by micro-vinifications (to release the smoke aromas) in the days leading up to harvest to assess the extent of the problem (and determine what action may be needed);
  2. Smoke aroma precursors are believed to be present on the inside of the grape skin, so how the grapes are handled can reduce the effect of smoke taint;
  3. Hand harvesting, gentle or whole bunch pressing, lower fermentation temperatures and reduced maceration times can reduce the uptake of compounds;
  4. Flash détente and reverse osmosis can also help, but will not remove the taint completely.
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22
Q

How does phylloxera spread?

A
  • These aphids can fly and crawl through soil;
  • Commonly transported by humans on young vines;
  • Can be transported on vineyard equipment;
  • By irrigation water.
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23
Q

What are the symptoms of a phylloxera infestation?

A
  1. Patches of vines die of drought increasingly in size year over year;
  2. Vine roots are covered with the insects surrounded by yellow eggs;
  3. Swellings on older roots;
  4. Pale green leaf galls on the under-side of leaves;
  5. Slow, stunted shoot growth and leaf yellowing appears in roughly three years, then plant dies after around five years.
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24
Q

In what year was phylloxera first identified in Europe?

A

1863

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25
Q

What soils are immune to phylloxera?

A

Sandy soils

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26
Q

What are the options for grape growers to manage phylloxera?

A
  1. Use American rootstock and graft on vinifera scions;
    • V. berlandieri, V. riparia and V. rupestris;
  2. Create rootstock hybrids to balance protection to phylloxera and resistance to lime in the soil;
    • these new rootstocks can be bred for resistance to other pests and hazards, such as nematodes and drought;
  3. Match best rootstock and variety to soil type.
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27
Q

What are nematodes?

A

Microscopic worms that feed off of vines’ roots, reducing yield and vigor.

They can also transmit viral diseases, e.g. fanleaf virus.

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28
Q

Once a vineyard has nematodes, can they ever be eradicated or can the nematode population only be managed?

A

Can only be managed

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29
Q

What are the two most commonly occurring nematodes?

A
  1. Root-knot nematode;
  2. Dagger nematode.
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30
Q

How do nematodes spread?

A
  • Unclean nursery stock;
  • Irrigation water;
  • Vehicles.
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31
Q

How can grape growers combat nematodes?

A
  1. Leave the soil fallow for a number of years (very expensive as no crop is cultivated);
  2. Fumigate the soil, either by using chemicals (uncommon) or plough in a cover crop of mustard plant, which contains compounds that work as biofumigants, killing nematodes (common);
  3. Use nematode-resistant rootstocks, such as Ramsey and Dog Ridge (both V. champini).
  4. Buy heat-treated rootstocks (steamed at 44ºC for 120 minutes).
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32
Q

How do grape moths damage vines?

A

They feed on flowers and grapes, creating wounds in the grapes thereby inviting disease and botrytis.

Because many moth species have several generations per season, one generation can attack flowers in spring and the next generation can attack grapes later in the year.

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33
Q

How do grape growers manage grape moths?

A
  1. Insecticide;
  2. Biologically:
    • introducing natural predators;
    • sexual confusion (using pheromone capsules to disrupt mating);
    • the bacterium Bacillus thuringiensis.
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34
Q

What type of mite is most detrimental to grape vines?

A

Spider mite

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35
Q

How do spider mites damage grape vines?

A

They feed on the surface cells of leaves, causing:

  • discoloration of the leaves;
  • reduction in photosynthesis;
  • delayed ripening;
  • reduction in yields.
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36
Q

What is the spider mite’s favorite environment?

  • Hot + humid
  • Cool + windy
  • Dry + dusty
A

Dry + dusty

They also thrive when the vine is water stressed

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37
Q

How do grape growers manage spider mites?

A
  1. Use water sprinklers and/or cover crops or mulches to reduce dust;
  2. Encourage predators;
  3. Specific sprays to kill only the mites that are problematic, but this can add to costs.
38
Q

Leafhoppers and ladybirds are:

  • Insect pests found in vineyards
  • Preparations used in biodynamic viticulture
  • Common names for oidium and peronospera
A

Insect pests found in vineyards

39
Q

____ is the bird species that often attacks vineyards.

A

Starling

Listen to and see what Starlings look like here.

40
Q

How are birds threats to vineyards?

A

They damage or destroy grapes which can lead to bacteria and disease entering the grapes, leading to rot.

41
Q

How do grape growers manage birds in their vineyards?

A
  1. Where birds are major threats, netting costs can be justified in high value areas;
  2. Bird scarers or noises which must be rotated regularly to avoid the birds acclimatizing to them;
  3. Falcons are sometimes used to deter unwanted birds.
42
Q

What is the best way to keep mammals out of vineyards and destroying crops?

A

Fencing – must ensure it’s high enough so they can’t jump over and plant them deep enough into the ground so that burrowing mammals can’t go under them.

43
Q

Powdery Mildew is caused by what fungus?

A

Erysiphe necator (also commonly called Oidium tuckeri)

It is a fungus specific to grape vines.

44
Q

Name two grape varieties that are more susceptible to Powdery Mildew.

A
  1. Chardonnay;
  2. Cabernet Sauvignon.
45
Q

Name two grape varieties that are less susceptible to Powdery Mildew.

A
  1. Riesling;
  2. Pinot Noir.
46
Q

Powdery Mildew thrives in which of the following conditions:

  • Hot + humid
  • Temperate + shady
  • Cool + rainy
A

Temperate + shady

47
Q

Powdery Mildew attacks what part of the vine?

A

Young, green parts of the vine – starts as dull grey patches which become black patches as they progress.

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

See what it looks like here.

48
Q

How do grape growers manage Powdery Mildew?

A
  1. Keep an open canopy to reduce shade and density of leaves (preferred approach);
  2. Sulfur applications help prevent and treat the disease (spraying early in the season is best, shortly after budburst);
  3. Systemic fungicides (not washed off by rain); but applications must be limited so the fungus doesn’t develop resistance.
49
Q

Downy Mildew is caused by what fungus?

A

Peronospora

It’s a water mold that lives within vine tissue.

50
Q

What part of the vine does Downy Mildew attack?

A

Green parts of the plant, especially young leaves and flowers.

51
Q

How does Downy Mildew reduce yields?

A

By defoliating the vine

52
Q

What are the conditions Downy Mildew needs to spread?

  • Moderate temperatures + rainfall
  • Hot + dry conditions
  • Cool + windy conditions
A

Moderate temperatures and rainfall

53
Q

What does Downy Mildew look like?

A

Yellow, circular ‘oil spots’ and then white, downy fungal growth on the underside of leaves.

See images here.

54
Q

How do grape growers manage Downy Mildew?

A
  1. Sprays made from copper salts (Bordeaux mixture, which is copper sulfate + lime) have traditionally been used to prevent the spread of Downy Mildew;
  2. Other fungicides – best applied about a month after budburst to véraison;
  3. Good drainage and an open canopy that dries quickly are helpful to avoid the fungus developing and spreading.
55
Q

What is the fungus that causes Grey Rot?

A

Botrytis cinerea

56
Q

What kind of varieties are most susceptible to Grey Rot?

A

Those with tight bunches or thin skins:

  • Sémillon
  • Sauvignon Blanc
  • Pinot Noir
57
Q

What conditions do Grey Rot spores need to become active?

  • Humid + rainfall
  • Dry + dusty
  • Cool + windy
A

Humid + rainfall

58
Q

How do grape growers manage Grey Rot?

A
  1. Choosing varieties that have small grapes with thick skins which give them high levels of resistance;
  2. Keeping an open canopy and removing the leaves around bunches;
  3. Fungicides, best applied at key points in the season (e.g. when flowering is nearly complete, véraison);
  4. Biological control, e.g. using antagonistic bacteria.
59
Q

Eutypa dieback is also called ___ ___.

A

Dead arm

60
Q

In what part of the vine does Eutypa dieback live?

What does it do to the vine?

A

Lives in the trunk of the vine;

Leads to rotten wood in vines, reducing yields significantly and kills vines over a ten-year period if not remedied.

See the damage it causes here.

61
Q

How do vines become infected with Eutypa dieback?

Under what weather conditions do the spores spread best?

A
  • Through pruning wounds in the vine;
  • Spores spread in rainy conditions and moderate temperatures.
62
Q

How do grape growers manage Eutypa dieback?

A
  1. Pruning late and applying fungicide to pruning wounds;
  2. Cut back affected trunks 5–10 cm beyond the visible symptoms and treat with fungicide
    • dead wood must be burned to avoid spreading spores;
  3. Biological controls (e.g. Bacillus subtilis);
  4. Retrain from a sucker left on the trunk or removing the vine and replanting it.
63
Q

The Phomopsis fungus causes a reduction in:

  • Crop size
  • Leaf size
  • Root depth
A

Crop size

64
Q

In what conditions does Phomopsis thrive?

A

Cool and wet springs followed by humidity and moderate temperatures.

65
Q

What happens to a vine that’s infected with Phomopsis?

A
  • Infected canes whiten and break off easily;
  • Shoots growing from these infected canes develop brown cracks at their bases;
  • Leaves are also affected.

See what Phomopsis looks like here.

66
Q

How do grape growers manage Phomopsis?

A
  1. Fungicides best applied three weeks after budburst and then again every two weeks if wet conditions persist;
  2. Diseased wood should be removed and burned;
  3. Improving air flow within the canopy to reduce risk of the disease.
67
Q

What is Esca caused by?

In what climate does it thrive?

A

A complex group of fungal organisms that thrives in warmer, drier climates.

68
Q

What are the symptoms of Esca?

A

Tiger-striping of the leaves and spotting inside the wood.

69
Q

How does Esca enter the vine?

What does Esca do to the vine?

A

Enters through pruning wounds;

Reduces yield and leads to death within a few years.

70
Q

How do grape growers manage Esca?

A
  • Best management is prevention – no chemical controls exist;
  • Not pruning in the rain;
  • Disinfecting pruning wounds;
  • Removing prunings promptly from the vineyard;
  • Sourcing disease-free stock.
71
Q

Black rot, black-foot disease, Bot canker, and anthracnose are:

  • Bacterial diseases
  • Fungal diseases
  • Viral diseases
A

Fungal diseases

72
Q

Name two bacterial diseases.

A
  1. Pierce’s disease;
  2. Grapevine yellows.
73
Q

Where does the Pierce’s disease bacterium live in vine?

A

In the sap channels

74
Q

How does Pierce’s disease attack vines?

A

The bacterium clogs channels in the vine leading to shrivelling, dropping leaves, and the death of the vine between 1-5 years.

See the damage it does here.

75
Q

How is Pierce’s disease spread?

A

By the glassy-winged sharpshooter, an insect

76
Q

How do grape growers manage Pierce’s disease?

A
  1. Reducing insect population (e.g. by removing their habitat);
  2. Some chemical insecticides work;
  3. Introducing predators: a wasp that feeds on the eggs of sharpshooters has been effective;
  4. Strict quarantine rules for the movement of plants;
  5. Work is presently being done on developing Pierce’s Disease-resistant vines.
77
Q

Grapevine yellows is:

  • A group of diseases caused by a type of bacteria
  • A viral disease
  • A fungal disease
A

A group of diseases caused by a type of bacteria

78
Q

How is grapevine yellows spread?

A
  1. Vectors (an organism that transmits a disease), including leafhoppers;
  2. Untreated, diseased stock sold by nurseries.
79
Q

What is flavescence dorée?

A

The most common type of grapevine yellows.

80
Q

What are the symptoms of grapevine yellows?

A
  1. Delayed budburst;
  2. Drooping posture because new shoots fail to lignify;
  3. Canopy turns yellow (in white varieties) and red (in black varieties).

See what it looks like here.

81
Q

How do grapevine yellows affect the crop?

A
  1. Reduced yields;
  2. Reduced quality (high acidity and low sugar content of grapes).
82
Q

Two of the most vulnerable grape varieties to grapevine yellows are:

A
  1. Chardonnay;
  2. Riesling.
83
Q

How do grape growers manage grapevine yellows?

A
  1. There is no control for grapevine yellows;
  2. The focus is on controlling the vector:
    • reduce leafhopper populations with insecticides;
    • remove plants that host the hoppers, including cover crops;
  3. Best practice in the nursery is to bathe the pruning wood in hot water to kill the disease.
84
Q

Name two viral diseases that affect grapevines.

A
  1. Fanleaf virus;
  2. Leafroll virus.
85
Q

What are the symptoms of fanleaf virus?

A
  • Early shoot growth is stunted;
  • Canes can grow in distorted ways;
  • Leaves are very pale, malformed and can look like a fan.

See what it looks like HERE.

86
Q

How is fanleaf virus spread?

A
  1. Dagger nematode;
  2. Grafting on infected plant material.
87
Q

Name a variety susceptible to fanleaf virus.

A

Cabernet Sauvignon

88
Q

How do grape growers manage fanleaf virus?

A

There is no cure for the disease – affected vines will have to be removed, adding to cost;

Before vineyards are replanted, soil tests should be done to check for the presence of dagger nematodes and only virus-tested, clean planting material should be used.

89
Q

How leafroll virus is spread?

A
  1. Mealy bugs;
  2. Grafting on infected plant material.
90
Q

How does leafroll virus affect grape vines?

A
  • Slows growth of roots and shoots;
  • Surviving fruit may take several additional weeks to ripen and may have more acidity, less color and lower sugar levels;
  • Overall health of the vine is also affected as it stores less carbohydrates.
  • Reduces yield by up to half and affect quality negatively.

See what it looks like here.

91
Q

Since some vines and rootstocks carry the leafroll virus without showing symptoms, what must a grape grower do prior to planting new vines?

A

Get them tested for the virus in a lab

92
Q

How do grape growers manage leafroll virus?

A
  • No cure for leafroll virus – only solution is to remove unproductive vines and replant with virus-free stock;
  • Keep an open canopy to reduce humidity, which reduces mealy bug population;
  • Introduce predators of mealy bugs, e.g. ladybugs and lacewings;
  • Nurseries can screen vines for virus infections.

WSET® Level 4 D1 Wine Production (11 decks)

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