Hazards

Question 1

Name the 9 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 1

What is the minimum amount of water vines need per year in cool climates?

Answer 1

500mm per year

Question 2

What is the minimum amount of water vines need per year in warm climates?

Answer 2

750mm per year

Question 3

What happens when vines do not get enough water?

Answer 3

• 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 4

What are management options for drought?

Answer 4

1. irrigation systems
2. drought-resistant rootstock
3. drought-tolerant varieties

Question 5

What is a drought-tolerant variety?

Answer 5

Garnacha

Question 6

What is a drought-resistant rootstock?

Answer 6

Rootstocks from V. rupestris and V. berlandieri parentage (e.g. 11R and 140R)

Question 7

What are hazards associated with excess water?

Answer 7

• too much vegetative growth
• high humidity
• poor drainage, waterlogging

Question 8

What are problems associated with vegetative growth?

Answer 8

1. competition with grape ripening
2. fruit is too shaded
3. less ripeness

Question 9

What is a problem associated with high humidity?

Answer 9

Fungal disease

Question 10

What are problems associated with poor drainage and waterlogging?

Answer 10

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 11

Name some management options for excess of water

Answer 11

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

Question 12

What are problems associated with excess rainfall during pollination and fruit set?

Answer 12

• millerandage or coulure
• reducing the size of the crop
• potentially lowering quality

Question 13

What are problems associated with excess rainfall during the mid-season?

Answer 13

• can reduce the rate of ripening of fruit
• mild water deficiency before veraison reduces the growth of shoot tips, allowing the grapes to ripen more satisfactorily

Question 14

What are 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

What are management option 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

What are low temps at which the vine can be seriously damaged, or even killed by winter freeze?

Answer 16

-20C/-4F

Question 17

What are the 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

What are types of climates that are most affected by winter freeze?

Answer 18

Continental climates, e.g. Canada and China

Question 19

What are general management options for freeze?

Answer 19

1. site selection
2. choice of varieties
3. protecting vines

Question 20

What are decisions made during site selection to combat freeze?

Answer 20

1. hillside sites can be up to 5C/9F 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

What are 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 labor 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

What are climates prone to spring frosts?

Answer 23

• wide range of climates
• cool climate areas are vulnerable, though the vine responds to regular low temps by not growing until a mean air temp of 10C/50F 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

What are 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, cold 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

What are 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

What are three actions growers can take to mitigate the effects of frost?

Answer 28

1. water sprinklers (aka aspersion) 2. wind machines 3. oil or propane gas burning heaters and wax candles

Question 29

Describe how water 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, 4-7m high, pull warmer air from above down to ground level, raising the temp - effective where there is an inversion layer, a warm air zone 10 m above hte ground (+3-5C/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 vineyard around the vines

Question 32

What are ways that hail can affect 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

What are two regions that suffer badly from hail?

Answer 33

Argentina Burgundy

Question 34

What are 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 risk of hail

Question 35

What is the 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, increases susceptibility to rot (due to skin damage)

Question 36

What are five management techniques 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

Where are three regions where fire is a vineyard hazard?

Answer 37

Australia California Chile

Question 38

What are three ways that wineries and vineyards can prepare for the risk of fire?

Answer 38

1. installing fire detectors and sprinklers 2. installing and maintaining a water tank 3. providing employee training for action in the even of an emergency

Question 39

Describe smoke taint and its effects.

Answer 39

- smoky or plastic aromas in the final wine - the effect on fruit increases in the period from veraison onwards - these compounds only become aromatic through the fermentation process - the strength of the aroma can increase during the aging of wine and during bottle aging

Question 40

What are four management options for smoke taint?

Answer 40

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 temps, and reduced maceration times 3. flash detente and reverse osmosis can also help, but will not remove the taint completely 4. blending with unaffected wines