8 - HAZARDS, PESTS & DISEASES Flashcards
What are the three effects of Hazards, pests and diseases on all of the world’s vineyards?
- Substantially reduced yields
- Negative effect on fruit quality
- Are expensive to manage/prevent
What are the eight hazards that can effect vineyards?
- Drought
- Excess of water
- Freeze
- Frost
- Hail
- Sunburn
- Fire
- Smoke taint
How much annual rainfall do cool climates and warm climates need?
Cool climates - 500mm
Warm climates - 750mm
What happens to a vine in drought? (x3)
- Water stress leads to stomata in leaves closing, and photosynthesis halting.
- Vine growth slows, development is reduced, ripening slows
- Eventually leaves fall off and the vine dies.
What are the three management strategies for dealing with drought?
- Irrigation - must be at vineyard establishment, very expensive otherwise
- Select drought resistant rootstocks - rupestris, berlandieri.
- Select drought tolerant varieties - eg Grenache
What happens to a vine that is exposed to excess water? (x6)
- Too much vegetative growth in summer
- Too much shade
- Competition for nutrients
- Increase risk of fungal disease
- Water logging roots in non-free-draining soils. Less oxygen intake, plant dies.
- compacts soil, harder to work.
What are the three management strategies for dealing with excess water?
- Site selection - free drained soil site.
- Plant on slope to assist drainage
- Construct drainage system if necessary
A fully dormant vine is able to resist cold temperatures. But at what temperature is the vine at risk of damage or death during winter dormancy?
Below -20deg C
What parts of the vine are the most, and the second most at risk of winter freeze?
Most at risk - Graft of grafted vines
Second most at risk - Canes and cordon
(all are above ground)
What climates are most at risk of winter freeze? (give two examples)
Strong continental climates.
Eg. China and Canada
What are the four preventative measures that can help to avoid winter freeze?
- Aspect - planting on hillside can be 5C warmer than the valley floor.
- Proximity to water - large bodies of water will help to regulate temperatures (eg Finger Lakes)
- Plant where snow will be deepest as this can protect the vine.
- Choose varieties that can withstand cols temperatures (eg Riesling, Cabernet Franc, or non-Vinifera species or hybrids eg Concord)
What are the three non-preventative management strategies for dealing with winter freeze?
- ‘Hilling up’ - soil around the base of the vine
- Burying the vine - in extreme circumstances, very expensive for labour (eg China)
- Train the vine to have multiple trunks, so that any that are lost can be replaced.
What are the conditions that allow for frost to occur?
Cold air below 0C gathers just above the surface.
What are the effects of frost on the vine?
The cold air temperature freezes the water inside the buds or shoots.
If they are young, their water content is high and they can die.
In relation to frost, what happens to a vine that is planted in a consistently cool area?
The vine will adjust, and won’t start growing until the temperature is at least 10C
What kind of areas are most vulnerable to frost damage?
Moderate or warm climates where the vine has not adjusted, it starts growing and is then damaged.
What are the three problems with secondary shoots that grow after frost damage?
- They are less productive
- They will ripen slower
- They will be more likely to be affected by rain or frost in autumn
What are the two kinds of frost? Describe each one.
- Advective: large volumes of cold air move in from cold areas
- Radiative: result of cool, still nights where the radiant heat from the soil that has accumulated in the day time is lost at night. Collects in valleys when there is no wind.
What are the five methods for reducing the risk of frost damage?
- Site selection - avoid frost pockets.
- Delay pruning - which will delay budburst
- Choose late budding varieties - eg Riesling
- Train vines higher on the trellis where the air is warmer
- Avoid cover crops as bare soil will retain heat better.
What are the three management strategies that can be utilised when frost threatens?
- Sprinklers (aspersion). Preferably from pre existing irrigation systems (drip irrigation is ineffective)
- Wind machines - large fans that pull warm air from the inversion layer (costly, but investment justified if frost risk is 20%). Helicopters do the same thing.
- Oil or propane burners (smudge pots) or wax candles (bougies). Expensive for labour and materials, also fairly ineffectual. Also pollutants.
What is an ‘Inversion Layer’?
A layer of warm air 10m above the ground that can be 3-5C warmer than ground temperature. Large fans (or helicopters) can suck this air down to the ground to combat frost.
What are the effects of hail?
- Damage to young leaves/shoots
- Damage to ripening fruit - increasing fungal disease risk
- Reduced yields in both current and next season
Hail is not very common worldwide, but what are two places that have suffered repeatedly?
- Burgundy (Champagne/Chablis)
2. Argentina (Mendoza)
Hail can be threatening at a number of stages, but when is it most detrimental?
After budburst and during ripening (spring & summer).
Buds can reshoot if the damage is early enough in the season.
What are the four management strategies for dealing with hail?
- Fire rockets with silver iodide into clouds to cause rain instead of hail.
- Net the fruit zone for protection where hail is common. (Mendoza). Not suitable for cooler climates as the nets provide shade.
- Play the odds with planting selection. Hail is selective, so keep continuity of supply by planting across a number of different plots.
- Vineyard insurance against hail. Consider the cost.
What are the conditions that allow for sunburn?
Prolonged hot weather with sun exposed grapes.
Risk increases when vines are already water stressed.
Why do grapes get sunburn but leaves and shoots don’t?
Grape transpiration is less effective that leaf transpiration, meaning that grapes release less water for cooling, and can therefore be a higher temperature than surrounding leaves.
What are the effects of sunburn? (x4)
- Reduced yield as burnt grapes need to removed at sorting.
- Negative impact on quality - browning of the skin, bitter taste
- Leads to scars on the grapes, and even death
- Skin damage leads to increase risk of disease.
What are the four management techniques for sunburn?
- Vineyard establishment - Aspect and orientation. N/S row orientation is best
- Canopy management to increase shading
- Irrigation to relieve water stress in a heatwave
- Agricultural sunscreen, or cloth/net shading
What are the climatic circumstances necessary for fire to occur?
Hot and dry climates,
Warmer, drier weather associated with climate change has increase occurances.
What regions have most recently been at risk from fires?
Australia, California, Chile
What geographical and vineyard features can increase risk of fire?
Close to wooded areas, pastural land or other crops.
Cover crops in the vineyard acting as fuel
What are the effects of fire?
- Total loss of vineyard
- Damage to property, trellising, irrigation
- Long recovery
- Loss of life
- Smoke taint
What are the three preventative management strategies for fire?
- Install detectors/sprinklers
- Install and maintain a water tank.
- Train employees in what to do in the event of a fire.
What are the effects of smoke taint?
- smoky or plastic like flavours
- smoke aroma compounds enter the grape and bind with sugars to form aromaless precursors that are only detectable aromatically after fermentation
- Can get worse with bottle age.
At what stage is smoke taint most detrimental?
During the growing season. Specifically increased from veraison onward
What are the four strategies for management of smoke taint affected grapes?
Note that nothing can remove it completely
- Testing - either analytically or by microferment
- Handling - hand picking, gentle whole bunch press, cooler ferment, less maceration (the compounds are thought to attach themselves to the inside of the skins)
- Flash detente or reverse osmosis.
- Blend with unaffected grapes/musts/wine
What are pests, and how do they interact with the vine?
Pests are organisms that attack the vine and impact it negatively. (INSECTS)
Some compete for water/nutrients.
Some attack the vine directly.
Some are the result of human travel (eg Phylloxera, Downy and Powdery mildew)
Some already exists in the vineyard area.