Hazards

Question 1

Name the nine main hazards.

Answer 1

1. Drought
2. Excess of Water
3. Untimely Rainfall
4. Freeze
5. Frosts
6. Hail
7. Sunburn
8. Fire
9. Smoke Taint

Question 2

Minimum amount of water vines need per year in cool climates.

Answer 2

500mm per year

Question 3

Minimum amount of water vines need per year in warm climates.

Answer 3

750mm per year

Question 4

What happens when vines do not get enough water?

Answer 4

• Vine will close the stomata on their leaves to limit water loss.
• Reduces photosynthesis
• Slows growth and ripening
• Reduces grape size
• Lower yields, unripe grapes
• Leaf loss, death

Question 5

Management options for drought.

Answer 5

1. Irrigation systems
2. Drought-resistance rootstock
3. Drought-tolerant varieties

Question 6

Drought-tolerant variety.

Answer 6

1- Garnacha
2 - Mourvèdre
3 - Zinfandel

Question 7

Drought-resistance rootstock.

Answer 7

Rootstocks from V. rupestris and V. berlandieri parentage (e.g. 110R and 140R).

420A

Question 8

Hazards associated with excess water.

Answer 8

• Too much vegetative growth
• High humidity
• Poor drainage, waterlogging

Question 9

Problems associated with vegetative growth.

Answer 9

1. Competition with grape ripening
2. Fruit is too shaded
3. Less ripeness

Question 10

Problem associated with high humidity.

Answer 10

Fungal Disease

Question 11

Problems associated with poor drainage and waterlogging.

Answer 11

1. Prohibits oxygen from getting to the roots
2. Slows growth
3. Can kill the vine
4. Difficult to work / uncontrollable water run off

Question 12

Name some management options for excess of water.

Answer 12

• planting on a slope
• planting on free-draining soil
• construction of a drainage system

Question 13

Problems associated with excess rainfall during the mid-season.

Answer 13

• Can reduce the rate of ripening of fruit.
• Mild water deficiency before véraison reduces the growth of shoot tips, allowing the grapes to ripen more satisfactorily.

Question 14

Problems associated with heavy rainfall close to the vintage.

Answer 14

• Grapes swollen with water (reducing the concentration of the must and with it the quality of wine)
• Grapes splitting (grey rot)
• Makes harvest very difficult (difficulty using mechanical harvesters, accessing the vineyard if on clay soils)

Question 15

Management options for untimely rainfall.

Answer 15

Mitigation:
- Choice of site (climate in general, slope)
- Condition of the soil
- Adequacy of drainage
- Monitoring weather forecasts (early harvest)

Question 16

Low temperatures at which the vine can be seriously damaged or even killed by winter freeze.

Answer 16

−20°C / −4°F

Question 17

Parts of the vine that are most at risk from winter freeze.

Answer 17

1. The joint at which the vine is grafted onto rootstock,
2. Canes or cordons

Question 18

Types of climates that are most affected by winter freeze.

Answer 18

Continental climates e.g. Canada, China

Question 19

General management options for freeze.

Answer 19

1. Site selection
2. Choice of varieties
3. Protecting vines

Question 20

Decisions made during site selection to combat freeze.

Answer 20

1. Hillside sites can be up to 5°C / 9°F warmer than the valley floor.
2. Vineyards near large or deep bodies of water benefit from a moderating effect.
3. Vines should be planted where snow settles most thickly, as a deep layer of snow protects the vine.

Question 21

Three methods of protecting vines from freeze.

Answer 21

1. “Hilling Up” - Building up soil around the vine graft as the soil underground is only a few degrees below freezing.
2. Burying vines - Very costly approach as it requires a lot of labour every year (China)
3. Vines can also be pruned to have several trunks so that those killed in winter can be replaced.

Question 22

When are frosts most hazardous for vines?

Answer 22

In spring during budburst, the new tender buds and shoots have a high water content so the frost kills them.

Question 23

Climates that are prone to spring frosts.

Answer 23

• Wide range of climates
• Cool climate areas are vulnerable though the vine responds to regular low temperatures by not growing until a mean air temperature of 10°C / 50°F is reached.
• Warmer areas are vulnerable because the vine begins to grow and will be damaged if there is a drop in temperature.

Question 24

Two types of frosts.

Answer 24

1. Advective frosts
2. Radiative frosts

Question 25

Define advective frost.

Answer 25

Large volumes of cold air moving from cold areas to warm areas.

Question 26

Define Radiative frost.

Answer 26

• Result of heat being lost on still, cool nights.
• The earth is heated by the sun during the day and releases it during the night.
• The amount of heat lost depends on the level of cloud cover.
• Windless nights allow a layer of freezing cold air to develop just above the surface of the soil.
• Cold air is denser than warm air, this freezing cold air will collect in valley bottoms.

Question 27

Five actions that can be taken to reduce the risk of frost.

Answer 27

1. In site selection, care must be taken to avoid frost pockets.
2. Delaying pruning postpones budburst into warmer months.
3. Choosing a variety that buds late, such as Riesling.
4. Vines trained high off the ground
5. Having bare soil between the vines

Question 28

Three actions grape growers can take to mitigate effects of frost.

Answer 28

1. Water sprinklers (also known as aspersion)
2. Wind machines
3. Oil or propane gas burning heaters and wax candles

Question 29

Describe how waters sprinklers can combat frost.

Answer 29

• Sprinklers installed
• As water freezes around the parts of the plant, it releases latent heat, protecting the plant
• The system must be kept on until the temperature rises

Question 30

Describe how wind machines combat frost.

Answer 30

• Large fans, 4-7 m high, pull warmer air from above down to ground level, thereby raising the temperature.
• Effective where there is an inversion layer, a warm zone of air 10 m above the ground (+3-5°C / 5-9F)

Question 31

Describe how heaters combat frost.

Answer 31

• Placed in vineyards and lit when there is a risk of frost.
• Heat the air in the vineyards around the vines.

Question 32

Ways that hail can effect the vines.

Answer 32

-Damages and rips off young shoots and leaves.

• Ripening grapes can both be damaged and become a point of entry for botrytis and other diseases.

Question 33

Two regions that suffer badly from hail:

Answer 33

Argentina

Burgundy

Question 34

Four ways to combat hail:

Answer 34

1. Silver iodide rockets to seed rainfall rather than hail
2. Netting the vines to protect the ripening grapes
3. Seek plots in different areas to ensure continuity of production
4. Insure against the risk of hail

Question 35

Effect of sunburn on grapes.

Answer 35

1. Scars on the skin of the grape and, in extreme cases, to the eventual death of the grapes
2. Lowers grape quality - browning of the grape - a bitter taste - increased susceptibility to rot (due to skin damage)

Question 36

Five management options for sunburn:

Answer 36

1. Row orientation and aspect can reduce the impact of the hottest afternoon sun.
2. Canopy management techniques to adjust the amount of direct sun exposure.
3. If a heatwave is forecast, additional irrigation, where allowed, may be applied to reduce water stress and sunburn.
4. Special agricultural sunscreen spray can be applied
5. Vines can be shaded with a cloth or net.

Question 37

Three ways that wineries and vineyards can prepare for the risk of fire:

Answer 37

1. Installing fire detectors and sprinklers.
2. Installing and maintaining a water tank.
3. Providing employee training for action in the event of an emergency.

Question 38

Describe smoke taint and its effects.

Answer 38

• ‘Smoky’ or ‘plastic’ aromas in the final wine
• The effect on fruit increases in the period from véraison onwards.
• These compounds only become aromatic through the fermentation process.
• The strength of the aroma can increase during the ageing of wine and during bottle ageing

Question 39

Four management options for smoke taint

Answer 39

1. Tested analytically and/or by micro-vinifications in the days leading up to harvest
2. Hand harvesting, gentle or whole bunch pressing, lower fermentation temperatures and reduced maceration times.
3. Flash détente and reverse osmosis can also help, but will not remove the taint completely.
4. Blending with unaffected wines.