Hazards Flashcards
(74 cards)
What is the minimum amount of rainfall vines need in cool and warm climates?
Cool climates- 500mm
Warm climates- 750mm
What happens to the vine if there is drought?
Leaves close their stomata- reduces photosynthesis.
If continues- grape size reduced, ripening slows down= unripe grapes and lower yields.
If prolonged- grapes lose their leaves and die
What are the ways of managing drought?
Irrigation
Rootstocks- V.berlandier/ v.rupestris parentage. eg 110R/140R.
Drought tolerant varieties eg garnacha
What does an excess of water do?
Too much vegetative growth- shades grapes from sun= less ripening and competes for sugars and nutrients
High humidity= fungal disease
Water logging= reducdes ox to roots= death.
Water logging- compaction of soils- hard to work
How does one manage an excess of water?
Slopes
Free draining soils
Construction of drainage system
What happens there is freeze?
-If temp falls below -20, vines dies.
-If vine grafted onto root stock, graft most at risk.
-Frost can kill cordons/canes= reduced yield and kill whole vine.
Canada, Washington State, China most at risk
How can one manage freeze?
1.Site selection
-hillsides can be 5 degrees warmer than valley floor
-near large bodies of water, eg large lakes in North America- moderates temp
-plant vines where snow settles most thickly= deep layer of snow provides insulation
2. Choice of varieties
-cab franc/Riesling
-American and Mongolian varieties do well, or a hybrid of one of these. eg V. amurersis
-eg concord variety
3. Protecting the vines
-burying the vines- costly (China)
-hilling up the vines- soil insulates the vine
-vines can be pruned to have several trunks, so those killed in winter can be replaced
What causes frosts and what does it do?
-When cold air below 0 degrees collects at ground level, freezing water in vines growing buds and shoots.
-If happens to newly burst buds/young shoots- kills them
-cool climes vulnerable- vine doesn’t grow until 10 degrees
warm climates vulnerable- vine starts growing- damaged with drop in temp.
If buds and shoots killed, secondary buds= less fruitful and longer to ripen= more likely affected by rain/autumn frosts.
What are advective frosts?
Large vols of cold air moving in from v cold areas
What is radiactive frosts?
-Heat being lost on still, cool nights.
-earth heated by sun during day, radiates during night.
-amount of heat lost depends on cloud cover.
-windless nights= layer of freezing cold air to develop above surface of soil
-cold air dense than cold air- collects in valleys
How can you reduce the risk of frosts?
-Site selection- hillsides, avoid frost pockets.
-Delaying pruning- warmer months.
-Late budding varieties- eg riesling
-High training- cold air at ground
-Bare soil between the vines- not cover crops= absorbs heat during day, radiates at night
What can you do when frost threatens?
1.Sprinklers- as water freezes around part of vine, releases latent heat, protecting vine. Must be kept on until temp rises.
-Running cost lower than wind/heaters- but not if cost of water high.
-only method to combat advective frost.
2. Wind machines- pull warm air from above down to ground level= raising temp
-effective where inversion layer of air 10m above ground
-initial cost
3. Oil/propane gas.
Disads- cost of labour and fuel, and for environment, not that effective, air pollution.
What effect does sunburn have to the grapes?
Grape transpiration more limited than leaf transpiration= grapes can reach higher temp= sunburn.
Browning, bitter taste, increased susceptibility to rot (skin damage)
= needs sorting =reduces yields
How can you manage sunburn?
- Row orientation and aspect. In n hemisphere, avoid E-W orientation or else southern side gets sunlight all day, and intense in the afternoon.
- Irrigation
3.Canopy management - Agricultural sunscreen/cloth/net
What is most at risk of fires?
Cover crops, mulches, woodlands, pastures= fuel to the fire
How can you manage fire risk?
Smoke detectors
Employee training
Installing and maintaining water tank
What happens to the grapes during smoke taint?
-effect on the fruit occurs from veraison onwards
-aroma compounds in smoke absorbed by grapes
-once in the grapes, compounds bind with sugar and aroma less precursors= compounds only become aromatic through ferm process
-strength of aroma can increase during ageing of wine and during bottle ageing
What are the management options for smoke taint?
- Affected must test analysis and/or micro-vinification to release smoke aroma in days leading up to harvest- establish extent of problem.
- Smoke precursors present in skins= handle carefully.
-hand harvest
-whole bunch pressing
-low ferm temps
-reduced maceration times
3.Flash detente, reverse osmosis. = helps but doesn’t remove completely
What are nematodes?
Microscopic worms
What damage to nematodes do?
Feeding off vine roots- significantly reducing yields and vigour
Transmit viral diseases- eg fanleaf virus spread by nematode
How are nematodes spread?
Unclean equipment, irrigation water, machinery
Unclean nursery stock
How can nematodes be managed?
Fumigate the soil
Plough mustard cover crops- contains biofumigant- kills nematodes
Rootstocks- Dog ridge and Ramsey
Plants from nurseries need to be heat treated to kill the nematodes
What do grape moths do?
-Feed on flowers in spring, and grapes later on in year.
=Wounds cause bacteria and fungi- crop loss
What are some examples of grape moths?
Light brown apple moth- Australia
European grapevine moth
