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Summary D1 | Pests and Hazards
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Complete summary, accurate to textboox, of D1 chapter 8 pests and diseases.
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8. HAZARDS, PESTS AND DISEASESManagement Options
Water: 500 mm in cool climates / 750 mm in warm climates à lack causes the vine to 1. If allowed, irrigation systems should be considered in the initial design of the
close the stomata in order to limit water loss, which reduces photosynthesis. The vineyard – some EU appellations only allow emergency irrigation
growth can be impaired, grape size is reduced and ripening slows down à unripe 2. Drought-resistance rootstocks (e.g. 110R and 140R from V. rupestris and V.
DROUGHT grapes and lower yields à If prolonged, vines lose their leaves and die. berlandieri parentage)
In regions that depend on irrigation, if drought continues over several years, water 3. Drought-tolerant variety (e.g. Garnacha)
may become so scarce that its use for irrigation is not allowed à entire vineyards (e.g.
high-volume Olifants River, South Africa) can be lost.
o Summer à too much vegetative growth, which can compete with grape ripening If it’s a regular hazard, then the planning of the vineyard must address it:
and fruit is too shaded less ripeness) 1. Planting on slopes
EXCESS OF o Prone to fungal diseases (high humidity) 2. Free-draining soils
WATER o Waterlogging (little oxygen available) à compaction of the soil à difficult to work 3. Drainage system
and uncontrolled water run-off
o During pollination and fruit set: risk of millerandage of coloure Nothing can be done, but choice of site, condition of the soil, whether or not to grass
UNTIMELY o Summer: reduce the rate of fruit ripening land, adequacy of drainage can mitigate.
RAINFALL o Heavy close to vintage: grapes swollen with water, splitting à grey rot / working Monitoring weather forecast: to early harvest or taking the chance
the harvest difficult (e.g. in using mechanical harvesters or pickers accessing the site
on clay soils
Hazards Fully dormant vines are relatively hard and can tolerate quite severe frost à if T fall 1. Site selection: hillside up to 5°C warmer than valley floor / large bodies of water
below –20°, the vine can be seriously damaged or killed by winter freeze. have moderate effects / thick snow settlement to provide insulation
If grafted vines, the rootstock is the part most at risk, then canes or cordons. 2. Choice of varieties: e.g. Cabernet Franc or Riesling, more resilient / American and
FREEZE Strongly continental climates are the most affected areas (e.g. Canada, Washington Mongolian vine species (V. amurensis) are winter hardy à e.g. Concord variety
State, China) (American hybrid) can withstand T down to nearly –30°C.
3. Protecting vines: hilling up (building up soil around the vine graft to help insulate)
/ burying vines: can be some of the costliest operations in the vineyard / vines
pruned to have several trunks so that can be replaced
Occur when cold air below 0°C collects at ground level, freezing water in the vine’s Reducing the risk:
growing buds and shoots / col winds after budburst are also very dangerous à if • In site selection must avoid frost pockets (places where cold air collects) and choose
freeze event happens to newly burst or young shoots that have a high-water content, it hillside sites
kills them à more shoots from secondary buds (less fruitful and will take longer to • Delay pruning postpones budburst into warmer months
ripen à more likely to be affected by rain or autumn frost) • Choosing a variety that buds late (e.g. Riesling)
a) Cool climate areas are vulnerable: the vine responds to regular low T by not • Vines trained high to offer more protection
FROSTS growing until a mean air T of 10°C is reached
• Having bare soil between the vines absorbs more heat during the day and radiates it
b) Warmer areas are vulnerable: the vine begins to grow and will be damaged in
there is a T drop during the night
When frost threatens:
Two types of frost:
1. Water sprinklers (aspersion): as water freezes around the parts of the plant, it
1) Advective frosts: caused by large volumes of cold air moving from very cold
releases latent heat, protecting the plant. The running costs can be much lower than
areas
wind machines or heaters, although not if the cost of water is high. Only method that
2) Radiative frosts: result of heat being lost on still, cool nights, which allow a layer
can be used to combat advective frosts.
of freezing cold air to develop just above the surface of the soil
2. Wind machines: large fans (4–7 m high) that pull warmer air from above down to
ground level, thereby raising T. Effective when these is an inversion layer, a warm
, FROSTS zone of air 10 m above the ground. Their investment is warranted if there is a chance
of a damaging radiation frost once every five years.
Helicopters may be used to create the same effect, worth it if the risk is sever but
short term.
3. Oil or propane gas burning heaters (smudge pots) and wax candles (“bougies”):
high cost of fuel and labour, low heating efficiency and contribution to air pollution.
Pellet of frozen rain that can cause severe damage to vines at various stages of • Rockets may be fired into thunderclouds, seeding them with silver iodide to cause
development à can damage and rip young shoots and leaves / ripening grapes can rainfall rather than hail
HAIL both be damaged and become a point of entry for botrytis and other diseases / yields • Netting à it creates some sharing, so it can be used only where there are high
can be seriously reduces sunlight levels
• Seek to have a number of plots in different areas: hail damage can be very selective
• Additional cost of crop insurance
Grape transpiration is much more limited, and therefore less effective, than leaf o In designing new vineyards, row orientation and aspect can reduce the impact of the
Hazards transpiration à grapes can reach higher T and the leaves and become burnt à scars hottest afternoon sun (avoid east-west row orientation)
on the skins and eventual death. o Amount of direct sun exposure can be adjusted (e.g. partially shading the fruit zone)
Higher risk on vines already in a situation of water stress. o If a heatwave is forecast, additional irrigation may be applied (where allowed)
SUNBURN Negative impact on grape quality: o Special agricultural sunscreen spray can be applied or vines can be shaded with a
• Browning of the grape cloth or net
• Bitter taste
• Increased susceptibility to rot
Typically need to be removed by sorting, which reduces yields
Vineyards that are near woodland, pastures or other crops may be more at risk as they • Installing fire detectors and sprinklers
FIRE provide fuel for the fire. Cover crops and organic mulches can also provide fuels, • Installing and maintaining a water tank
whereas fire spreads less easily though bare, cultivated soils. • Providing employee training for action
Smoke in the vineyard during the growing season can result in “smoky” or “plastic” ~ Affected must can be tested analytically and/or by micro-vinifications (to release
aromas in the final wine à the effect on fruit increases in the period from véraison the smoke aromas)
SMOKE onwards as aroma compounds in smoke can be absorbed by the grapes à these ~ It is thought that the smoke aroma precursors are present on the inside of the skin of
TAINT compounds bind with sugars and from aroma-less precursors, that become aromatic grapes, how the grapes are handled can reduce the effects à hand harvesting, gentle
only though fermentation. or whole bunch pressing, lower fermentation T, reduced maceration times.
The strength of the aroma can increase during ageing and bottle ageing, as further ~ Flash détente and reverse osmosis can also help, but will not remove it totally
aroma precursors break down and become aromatic ~ Blending with unaffected wines
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