8.1 Hazards Flashcards
Name the 9 main hazards.
- Drought
- Excess of Water
- Untimely Rainfall
- Freeze
- Frosts
- Hail
- Sunburn
- Fire
- Smoke Taint
What is the minimum amount of water vines need per year in cool climates?
500 mm per year
What is the minimum amount of water vines need per year in warm climates?
750 mm per year
What happens when vines do not get enough water?
- 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
What could happen in regions that depend on irrigation if drought continues over several years? Give an example of where this has happened.
- Water may become so scarce that the use of water for irrigation is not allowed
- Entire vineyards can be lost
- Example: Olifants River region of South Africa
Name some management options for drought.
- Irrigation systems
- drought-resistance should be high on the list of priorities in choosing a rootstock
- Choose a drought-tolerant variety
Name a drought-tolerant variety.
Garnacha
Name a drought-resistance rootstock.
rootstocks from V. rupestris and V. berlandieri parentage
e.g. 110R and 140R
Why could an excess of water become a hazard?
- Too much vegetative growth Which leads to: 1. Competition with grape ripening 2. Fruit is too shaded 3. Less ripeness
- High humidity
Which leads to:
1. Fungal diseases - Poor drainage, waterlogging
Which leads to:
1. Prohibits oxygen from getting to the roots
2. Slows growth
3. Can kill the vine
4. Difficult to work / uncontrollable water run off
Name some management options for excess of water.
- planting on a slope
- planting on free-draining soil
- construction of a drainage system
What could happen if there is excess rainfall during pollination and fruit set?
- millerandage or coulure
- reducing the size of the crop
- potentially lowering quality
What could happen if there is excess rainfall during the mid-season? Why?
- 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.
What could happen if there is heavy rainfall close to the vintage?
- 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)
Name some management options for untimely rainfall.
Mitigation:
- Choice of site (climate in general, slope)
- Condition of the soil
- adequacy of drainage
- Monitoring weather forecasts (early harvest)
Below what temperature can the vine can be seriously damaged or even killed by winter freeze?
−20°C / −4°F
What part of the vine is most at risk from water freeze? What is second?
- If vines are grafted onto rootstock, the graft is the part of the vine that is most at risk (if it is above the surface of the ground).
- Canes or cordons
What types of climates are most affected by freeze? Give 3 examples.
- Strongly continental climates
- Examples: Canada, Washington State, China
Name 3 very general management options for freeze.
- Site selection
- Choice of varieties
- Protecting vines