Ch 8 Hazards, Pests and Diseases Flashcards
Hazards, Pests, Diseases
What are the 9 main hazards?
Water related:
* drought
* too much water
* untimely rainfall
* freeze
* frost
* hail
Heat/light related
* Sunburn
* Fire
* Smoke taint
Hazards, Pests, Diseases
What is minimum amt of water needed by vines (cool vs warm climate)?
Cool - min 500mm
Warm - min 750mm
Hazards, Pests, Diseases
How does drought affect vines?
What are management options for drought?
Effect on vine:
○ Stomata on underside of leaves close to conserve water-> reduced phs -> impact size of vine, reduced grape size, ripening slows = lower yields and unripe grapes
○ If prolonged -> vines lose leaves and die
○ If extreme, regions that rely on irrigation may be restricted -> can kill entire vineyards (Olifants River SA)
Management Options: ○ Irrigation - consider as part of vineyard establishment; can be installed later but much more \$\$/complex; restricted in parts of EU ○ Drought-resistant rootstock (at vineyard estab) - ex v rupestris and v berlandieri 110R and 140R ○ Drought tolerant grape var (Garnacha)
Hazards, Pests, Diseases
What are impacts of too much water?
What are management options?
By timing/season
Impacts:
○ Summer - excessive vine growth -> compete with grape ripening and too much shade
○ Fungal disease pressure - high humidity
○ Waterlogging - non free-draining soils -> reduce amount of 02 avail to roots = slow growth and can eventually kill vine; compaction of soil -> hard to work and uncontrolled runoff
Management options:
* If in area of regular high rain -> plan when planting vineyard -> slope or free-draining soil or by making drainage system
Hazards, Pests, Diseases
What are impacts of untimely rainfall at key parts of growing cycle?
What are management options?
Timing impacts:
○ During pollination -> coulure or millerandage = reduced yields and can lower quality
○ Summer - slow fruit ripening
○ Harvest - heavy rain -> swollen grapes = lower quality, diluted sugar levels; grapes split = grey rot; makes harvest more difficult (esp machines on clay soils)
Management options:
○ Nothing can be done about timing of rain; but choice of site, condition of soil, grass the land bet vines, ensure some drainage
○ Monitor weather forecasts - early harvest -> less ripe fruit or take chance on weather improving
Hazards, Pests, Diseases
What are concerns about freezing conditions, what areas most impacted?
What are management options?
Concerns/areas impacted:
○ Temps <-20°C can damage or kill vines
○ Graft site most at risk in freeze (if above ground), canes/cordons next at risk
○ Frost can kill canes or cordons and/or kill all parts of vine above ground = reduced yield = replace vine
○ Areas with strong continental climates most affected - Canada, Washington, China
Management options:
* Site selection - Hillsides can be up to 5°C warmer than valleys, sites near large or deep bodies of water get moderated, plant vines where snow most accum -> snow insulates vine
* Grape Variety - plant freeze resistant var - Riesling/CS; some S Amer and Mongolian (v amurensis) and hybrids are very winter tolerant (e.g. Concord - v labrusca - can tolerate to -30°C
* Protect vines - build up soil around graft (hilling up); bury vines in extreme cond (costly/labor intensive); prune vines to have several trunks -> if some killed, can be replaced
Hazards, Pests, Diseases
How/when do frosts happen?
What is the impact and how does it vary cool vs warm climate?
○ Happen when cold air <0°C collects at ground level -> freezes water in vine’s growing buds and shoots; cold winds blowing thru vineyard also dangerous
○ If happens to newly burst buds or young shoots -> kills them = major impact on yields
○ Cool climate - they are vulnerable, tho vines delay budburst and growth until temps reach avg air temp >10°C
○ Warm climate - vine starts to grow and impacted if temps drop; if buds/shoots killed->vine puts out more shoots from secondary buds->less fruitful and take longer to ripen = potential problems in fall from rain or frost)
Hazards, Pests, Diseases
What are the 2 types of frost and how do they happen?
What are the 2 categories of management action?
2 types of frost:
○ Advective - caused by large vol of cold air moving in from cold areas
○ Radiative - heat lost on still, cool nights ->amt of heat lost depends on cloud cover (cloudless loses more heat) and wind (windless lets freezing air dev above surface -> freezing cold air collects in valley bottoms since cold air heavier than warm
Management actions:
* actions that reduce the risk
* actions that address frost when it happens
Hazards, Pests, Diseases
What is advective frost?
Frost that forms when cold air mass from very cold areas moves over region
Hazards, Pests, Diseases
What is radiative frost and what factors effect it?
Frost that forms due to heat lost on still, cool nights
* amt of heat lost depends on cloud cover (cloudless night cool faster) and wind (lack of wind lets freezing air develop just above land surface)
* freezing air collects in valley bottoms since cold air is heavier than warm
Hazrds, Pests and Diseases
How do vines react to frost and what is the impact?
Vines grow shoots from secondary buds
* Less fruitful
* Take longer to ripen
Hazards, Pests, Diseases
What are management actions to proactive reduce risk of frost?
○ Site selection - avoid areas with frost pockets and choose hillsides where cool air drains away
○ Delaying pruning - postpones budburst to warmer months; if buds at end of canes get frosted they can be
removed
○ Choose late bud var (Riesling)
○ Train vines high - above cold air near ground
○ Have bare soil bet vines (vs cover crop) -> absorbs more heat during day and radiates heat at night
Hazards, Pests, Diseases
What are 3 management actions to reduce impact once frost happens?
- Water sprinklers
- Wind machines
- Heaters/smudge pots
Hazards, Pests, Diseases
How do sprinklers reduce impact of frost?
What is another term for sprinklers?
Considerations - adv/disadv
What type of frost is this the only solution for?
Other term - aspersion
How sprinklers work:
§ as water freezes around plant (going from liquid to solid), it releases latent heat; must be kept on until temps rise
§ Can be used as part of irrigation, or put out to deal with frost conditions
§ Cost - equipment and water; cheaper than wind machines or heaters
§ ONLY option for advective frost
Hazards, Pests, Diseases
How do wind machines reduce the impact of frost?
What conditions are necessary for them to be effective?
What are economic considerations?
§ 4-7m high fans pull warmer air from above down to ground, raising temp
§ Effective when there is inversion layer - warm zone of air 10m above ground +3-5°C
§ Cost effective when there is risk of damaging radiative frost every 5yrs (20% chance in any one yr); signif initial investment; can also use helicopters - very expensive but can be worth it in extreme sit
Hazards, Pests, Diseases
How do heaters/smudge pots/wax candles work?
What are economic and other considerations?
§ Oil or gas heaters and wax candles put in vineyard when risk of frost.
§ High labor cost, cost of fuel, low heating efficiency, contributes to air pollution
Hazards, Pests, Diseases
What is hail?
How does it impact vines?
What are the implications (early vs late season)?
What are management options?
○ Pellets of frozen rain
○ Damage and rip young shoots and leaves, ripening grapes can be damaged and allow bot and other diseases
○ Significant yield impacts in first and following seasons; also lower quality fruit due to vine shift focus back to re-growth (if hail in early spring)
○ If early in season, vine may be able to re-shoot from existing buds
○ Hail is generally unpredictable, but Burg and parts of Argentina susceptible
Management options: ○ Rockets with silver iodide fired into clouds to cause rain vs hail ○ Net the fruit zone in areas with regular hail - creates shading so only used in areas with high sunlight -> better in Argentina than Burg ○ Plant grapes in multiple areas since hail damage usually very localized ○ Crop insurance
Hazards, Pests, Diseases
What is sunburn?
What are its impacts?
What are management options?
○ Prolonged hot weather can cause grape sunburn -> since grape transpiration much less effective at temp regulation than leaf transpiration -> grapes get hot and get burnt
○ Higher risk if vines have water stress
○ Causes scars on skin of grapes -> can kill grapes
○ Negative impact on quality - browning of grape = bitter taste; inc risk of rot due to skin damage => need to be removed = reduced yields
Management options:
○ Vineyard design - row orientation and aspect reduce hot afternoon sun exposure - avoid e/w exposure in N hemi
so grapes on S side not exposed to sun all day
○ Canopy management - shade fruit zones in hot regions
○ Heatwave forecast - additional irrigation if allowed -> reduce water stress
○ Special agriculture sunscreen spray
○ Shade vines with net
