Hazards Flashcards
Drought
Impact on vine/grapes:
1) lack of water = stomata’s close = reduced photosynthesis =
reduced grape size & slows ripening = reduced yield & unripe grapes
Management:
1) irrigation
2) drought resistant rootstocks
3) drought tolerant varietals
- minimum water needed: 500mm in cool climates, 750mm in hot climates
- over time can kill vine
Excess Water
Impact on vine/grapes:
1) too much vegetative growth = competition with grapes & increased shade
2) waterlogged roots = starves roots of oxygen = slows growth / death of vine
3) compaction, difficulty to work, uncontrollable water run-off
4) risk of fungal disease
Management:
1) planting on slope or free-draining soil
2) construct a drainage system
Untimely Rainfall
Impact on vine/grapes:
1) during pollination = millerandage & collure = reduction of yield and quality
2) during summer = reduced rate of ripening
3) close to harvest = swollen berries/ dilution and grape splitting/ risk of grey rot, makes harvest difficult
Management:
1) choice of site/ free-draining soil
2) grass between vine rows
3) monitoring weather forecasts
Freeze
Impact on vine/grapes:
1) graft, canes, and cordons are most at risk = decreased yields
Management:
1) site selection (hillsides, near bodies of water, plant where snow piles up for insulation)
2) resistant varieties or hybrids
3) “hilling up” or burying the vine
4) train multiple trunks so if any die the vine lives on
- occurs below 0C/32F
- under -20C/-4F can damage vines
- under -25C/-13F will kill vines
Frosts
(advective vs radiative)
Advective: large bodies of cold air moving in from cold areas
Radiative: result of heat being lost from the ground on windless, cool nights
Impact on vine/grapes:
1) if buds and shoots are killed the vine must rely on secondary buds = less fruitful and take longer to ripen
Management:
1) avoid frost pockets
2) delay pruning to delay budburst
3) late budding varieties
4) train vines high off the ground
5) have bare soil between vines as it holds warmth
6) sprinklers (advective)
7) wind machines (radiative)
8) oil/propane gas burners (radiative)
Hail
Impact on vine/grapes:
1) rip shoots and leaves
2) damage berries = allow for diseases
(If damage is early enough vine may be able to reshoot from existing buds)
Management:
1) netting
2) crop insurance
3) having vineyards in multiple locations
4) rockets that line clouds with silver iodide, causing ran rather than hail
Sunburn
Impact on vine/grapes:
1) scars on grape skin = increased disease risk
2) browning of grapes = bitter taste and increased disease risk
Management:
1) sorting = reduced yields
2) row orientation and aspect (NH never plant east-west)
3) canopy management to provide shade
4) additional irrigation before a heatwave
5) chemical agricultural sunscreen
Fire
Impact on vine/grapes:
1) destruction of vineyard, winery, etc
2) smoke taint that binds with grape sugars to form aroma less precursors that only become aromatic through fermentation = ‘smoky’ or ‘plasticy’ aromas
Management:
1) avoid planting near forests or woodlands
2) don’t use cover crops
3) fire detectors/ sprinklers
4) install a water tank
5) test effected musts with microvinifications to gauge extent of the problem
6) winemaking to avoid skin extraction = hand harvest, gentle press, low fermentation temps, reduced macerations
7) corrective winemaking = flash détente and reverse osmosis
Flash detente
- destemmed grapes are quickly heated to 85-90C/ 185-194F then rapidly cooled under vacuum
- a 2 minute process
- it bursts the cells in the grape skins, allowing for rapid extraction of anthocyanin and flavors
Reverse osmosis
- a form of cross-flow filtration
- removes a flavorless permeate of water and alcohol, distilled to remove alcohol then blended back
