D8: Hazards, Pests and Diseases Flashcards
Name 9 hazards which can have an impact on grape growing
- drought
- excess water
- untimely rainfall
- freeze
- frosts
- hail
- sunburn
- fire
- smoke taint
DROUGHT
what is the minimum amount of water a vine needs in a) cool climate and b) warm climates?
Cool: 500mm
Warm: at least 750mm
DROUGHT
what happens to the vine with lack of water?
- stomata closes in order to limit water loss
- this reduces photosynthesis which then stops the plant growing. This impacts the size of the grapes and ripening also slows
- causes unripe grape
- if has lack of water for too long, vines lose their leaves and die
DROUGHT
What can happen to vineyards where water is scarce and irrigation is limited? Give examples
- can lose whole vineyards
EXAMPLE: Olifants River in South Africa
DROUGHT
What are the management options for drought?
- irrigation (where permitted)
- drought resistant rootstock (e.g. 110R or 140R)
- drought tolerant grapes (e.g. garnarcha)
Name two drought resistant rootstock
100R and 140R
Name a drought tolerant grape variety
Garnacha
EXCESS WATER
Excessive water can lead to…
1) excessive vegetative growth
- too shady, too much competition for nutrients
- leads to less ripeness
2) fungal disease due to high humidity
3) waterlogged soils
EXCESS WATER
What is the impact of waterlogged soils?
- reduces oxygen in soil
- slows growth
- eventually kills the vine
- causes compaction in soil so difficult to work and can cause uncontrolled water run off
EXCESS WATER
What are the management options for Excess Water?
- slope planting
- free draining soils
- construction of drainage systems
UNTIMELY RAINFALL
What two conditions can this cause during pollination and fruit set?
- coulure
- millerandage
- reduces crop size and lowers quality
UNTIMELY RAINFALL
What else does this impact?
- rate and ripening of fruit as you want some water deficiency before veraison
UNTIMELY RAINFALL
What can happen if there is rainfall before harvest
- swollen and splitting grapes
- rot
- also makes machine harvesting difficult
UNTIMELY RAINFALL
What are the management options?
- think about site choice, soil and drainage adequacy
- monitoring weather around the harvest
FREEZE
At what temperature can a vine be killed or damaged?
- below -20 degrees/-4 Fahrenheit
FREEZE
What part of the vine is most at risk?
- graft
- then canes/cordons
FREEZE
What three places are most at risk
- Canada
- Washington State
- China
FREEZE
What are the management options?
- site selection
- hillsides are warmer than plains
- near a body of water
- plant where deep snow settles as protects vine
- varieties
- resilient (cab franc, riesling)
- winter hardy (Concord - tolerant up to -35 degrees or other mongolian varieties)
- protection
- hilling up/building soil around vine graft
- burying vines (often seen in China)
- prune vines to have several trunks so can replace any that are killed
FROSTS
What happens when freeze occurs?
- when cold air below zero degrees collects at ground level, it freezes water in vines growing buds and shoots
- will kills any newly burst buds or young shoots which have a high water content
- impacts yield and quality
FROSTS
Where is the risk highest for frost?
- areas with cool and warm climates
- if buds are killed, secondary buds take much longer to grow and establish
FROSTS
What are the two different types of frost which can occur?
ADVECTIVE FROSTS
- large volumes of cold air moving in from very cold areas
RADIATIVE FROSTS
- result of heat being lost on still, cool nights.
- allows for layer of freezing, cold air to develop just above the surface of soil.
- collects in valley bottoms
FROSTS
What are the management options?
- site selection (avoiding frost pockets)
- delay pruning so as to delay budburst
- chose late budding varieties
- train vines high
- have bare soil between vines so as to radiate heat at night
FROSTS
What can you do when frost threatens?
- water sprinklers: as water freezes around the plant, it releases latent heat and protects the plant
- wind machines: pulls warm air from above down to the ground level
- needs INVERSION LAYER: warm air zone 10m above ground
- expensive but main cost is upfront
- oil or propane heathers: placed around vineyards and lit when risk of frost
- costly, labour intensive and not environmentally friendly
HAIL
What damage can hail do to a vineyard?
- damage and rip young shoots and leaves
- damage grapes and become entry points for botrytis and disease
- reduce yield at the time and in future seasons