8. Hazard, Pests and Diseases

• Shedding netting improves fruit quality.
• Fruit quality can be improved via shading, canopy adjustment, and irrigation.
• Potential hazards include pests and diseases, specifically bacterial diseases.
• Challenges like hazards, pests and diseases impact nearly all the world’s vineyards.
• These can substantially reduce yields and negatively affect fruit quality.
• Prevention and management can significantly increase annual costs.

Drought

• Vines need sufficient water (500 mm/year in cool climates, 750 mm/year in warm regions) to grow and produce high-quality fruit.
• Lack of water causes vines to close stomata, reducing photosynthesis and impairing growth.
• Grape size decreases, ripening slows, and eventually, leaves drop, and the vine dies.
• Prolonged drought leads to water scarcity, making irrigation unviable and potentially destroying entire vineyards like in the Olifants River region of South Africa.

Drought Management Options

• Integrate irrigation systems into the initial vineyard design where allowed.
• Select drought-resistant rootstocks when planting new vineyards like V. rupestris and V. berlandieri (110R and 140R).
• Opt for drought-tolerant varieties such as Garnacha.

Excess Water

• Too much summer water leads to excessive vegetative growth and shaded fruit, resulting in less ripeness.
• High humidity from rainfall promotes fungal diseases.
• Waterlogging from poorly drained soils reduces root oxygen, slowing growth and potentially killing the vine, which can lead to soil compaction and uncontrolled water runoff.

Excess Water Management

• Plant on slopes or free-draining soil where possible to address excess rainfall.
• Use drainage systems to improve drainage.

Untimely Rainfall

• Excess rainfall during pollination reduces crop size and quality causing millerandage or coulure.
• Summer rain slows fruit ripening.
• Pre-véraison water deficiency aids grape ripening by slowing shoot tip growth.
• Heavy rainfall near vintage causes grapes to swell, diluting the must and leading to splitting and grey rot.
• Harvesting becomes difficult, especially on clay soils, hindering machine use.

Untimely Rainfall Management

• Site selection includes climate and slope considerations, soil condition, and drainage to mitigate rain effects.
• Winemakers might harvest early with less-ripe fruit or risk losing the crop, based on weather forecasts.

Freeze

• Dormant vines are hardy but can be damaged or killed if temperatures drop below -20°C / -4°F.
• Grafts are most at risk, followed by canes or cordons.
• Frost kills plant parts, potentially requiring vine replacement.
• Areas with continental climates like parts of Canada, Washington State, and China are most affected.

Freeze Management Options

• Site Selection:

  • Hillside sites are warmer than valley floors by up to 5°C / 9°F.
  • Vineyards near large bodies of water benefit from temperature moderation.
  • Plant vines where snow settles thickly for insulation.

• Variety Choice:

  • Select freeze-resilient varieties such as Cabernet Franc or Riesling.
  • American and Mongolian vine species (V. amurensis) and their hybrids are very hardy.

• Vine Protection:

  • Hilling up soil around the vine graft insulates it.
  • Burying vines is effective but costly.
  • Prune vines to have multiple trunks for replacement if some die.

Frosts

• Frosts occur when air below 0°C / 32°F collects, freezing buds and shoots.
• Cold winds after budburst are dangerous, killing newly burst buds with high water content, significantly impacting yields.
• Vines in cool climates delay growth until temperatures reach 10°C / 50°F. The warmer areas are damaged if temperatures drop after growth begins.
• Killed buds lead to less fruitful secondary shoots with delayed ripening.
• Advective frosts are caused by cold air masses, and radiative frosts result from heat loss on still nights.

Frost Management Options

• Risk Reduction:
  • Avoid frost pockets and select hillside sites.
  • Late pruning delays budburst.
  • Choose late-budding varieties like Riesling.
  • Train vines high off the ground where it is warmer.
  • Keep soil bare to absorb and radiate more heat.
• Threat Response:
  • Use water sprinklers to release latent heat as water freezes.
  • Wind machines pull warmer air from above.
  • Helicopters can mix air layers but are expensive.
  • Use Oil or propane heaters/wax candles but these have high costs and cause air pollution.

Hail

• Hail can severely damage vines and ripening grapes, creating entry points for botrytis and other diseases.
• Yields can be reduced in subsequent seasons.
• Early-season damage allows vines to reshoot.
• Hail is unpredictable but some regions (Argentina, Burgundy) suffer repeatedly.
• Netting can protect against hail.

Hail Management Options

• Rockets with silver iodide can induce rainfall instead of hail.
• Netting protects fruit zones in high-sunlight areas like Mendoza.
• Have multiple plots in different areas to ensure production continuity.
• Consider crop insurance.

Sunburn

• Excessive sunlight can cause sunburn on grapes, especially with water stress.
• Grapes, having limited transpiration, overheat and burn.
• Sunburn scars the fruit, leading to grape death, reduced quality, browning, bitter taste, and increased rot susceptibility.
• Affected grapes need to be sorted out, which reduces yields.

Sunburn Management Options

• Orient rows to reduce afternoon sun exposure, particularly in hot Northern Hemisphere regions where east-west rows should be avoided.
• Adjust sun exposure via canopy management to partially shade the fruit zone.
• Use supplemental irrigation to reduce water stress during heatwaves.
• Apply agricultural sunscreen or shade with cloth/netting.

Fire

• Fire is a serious hazard in hot, dry countries and is increasing due to climate change.
• Vineyards near woodland or pastures are more at risk as these provide fuel.
• Cover crops and organic mulches can also provide fuel, while bare soil slows fire spread.
• Fire damages property, equipment, and vines and creates smoke.

Fire Management Options

• Wineries/vineyards in fire-prone areas should install detectors/sprinklers.
• Establish and maintain a water tank.
• Train employees in emergency procedures.

Smoke Taint

• Smoke exposure during growing season can cause smoky/plastic aromas in the final wine.
• The effect on fruit increases from véraison onward, as aroma compounds from smoke are absorbed and bind with sugars, forming aroma-less precursors.
• The aroma strength increases during fermentation and aging as precursors break down.

Smoke Taint Management Options

• Test affected musts by micro-vinifications to assess the problem.
• Handle grapes gently: hand-harvest, whole bunch press, lower fermentation temperatures, reduce maceration times, reduce compound uptake.
• Flash détente and reverse osmosis can help but not eliminate the taint.
• Blend affected wines with unaffected wines.

Pests and diseases

• Pests are organisms negatively impacting vine and grape production by competing for resources or directly attacking the vine and grapes.
• Evaluate the seriousness and economic cost of pest attacks when deciding on the measures needed.
• Major pests/diseases often originate from importing insects/fungi into areas where vines lack natural resistance. Grafting American rootstocks onto European vines helps combat pests due to natural resistance.

Phylloxera

• Phylloxera is an aphid-like insect that damages grapevine roots, spreading via crawling, human activity and irrigation water.
• Damaged roots reduce water/nutrient uptake and are more vulnerable to secondary attack, can cause vine decline and death.
• Signs of phylloxera infestation include vines dying in patches, insects/yellow eggs on roots, swellings on older roots, pale leaf galls and stunted shoot growth.

Phylloxera Management Options

• Sandy soils are immune to phylloxera, but this isn't helpful for other soil types.
• Using American vine species V. berlandieri, V. riparia and V. rupestris provides protection by forming corky layers around eggs.
• Grafting European varieties onto American rootstocks helps avoid undesirable aromas from the resistant vines.
• Rootstock hybrids balance phylloxera protection and lime resistance.
• Rootstocks derived from American species address pests, nematodes, soil pH, and water stress.
• Grape growers should seek advice on rootstock/variety choice to suit vineyard soil.
• Planting on rootstocks is expensive but is a standard vineyard establishment cost.

Nematodes

• Nematodes are microscopic worms common in soils that can damage vine roots and reduce yields.
• Nematodes can transmit viral diseases, such as transmitting fanleaf virus by the dagger nematode.
• Types include root-knot and dagger nematodes are common. Present in the soil already or can be spread by unclean nursery stock, irrigation water or vehicles, and can only be managed and cannot be eliminated.

Nematodes Management Options

• Soil samples are taken to determine nematode type and numbers.
• Limited options are avaliable to combat them.
• Fumigate the soil after ploughing in a cover crop of mustard plant, but chemicals previously used for this method are now banned in most regions.
• Use nematode-resistant rootstocks from heattreated plants.
• Examples include Ramsey and Dog Ridge (both Vitis champini).

Grape Moths

• Grape moths damage vines by feeding on flowers and grapes, with multiple generations per season. Wounded flora create openings for bacteria and fungi that causes crop losses.
• Common types are light brown apple moth (Australia), European grapevine moth (southern Europe), and grape berry moth (North America).

Grape Moths Management Options

• Biological controls: Bacillus thuringiensis (toxic to moths), pheromone capsules (disrupt mating), and natural predators (parasitic wasps, green lacewings, and some spider species).
• Insecticides

Spider Mites

• Spider mites damage vines with detrimental results, the species differs by region.
• Pacific spider mite is destructive in California, while the red spider mite and two forms of yellow spider mite cause damage in Europe.
• They feed on leaves causing discoloration, reduced photosynthesis, late ripening, and yield reduction.
• Spider mites are further damaging in dusty conditions and cause the greatest damage to vines that are already water-stressed.

Spider Mites Management Options

• Inhospitable environment creation by water sprinklers and/or cover crops or mulches for dust reduction.
• Plant host species, beneficial pesticides, and other strategic sprays to encourage predatory mites that feed on spider mites
• General pesticides may kill beneficial predatory mites
• Specific sprays can be applied to kill only the mites that are problematic in the vineyard, but this can add to costs.

Birds

• Birds in vineyards damage grape crops, isolated vineyards are at higher risk.
• In addition to physical damage, the activity of birds allows bacteria and fungi to enter bunches and leads to rot. Starlings are one species that is aggressive towards vineyards.

Birds Management Options

• Total netting can protect high-value crops when birds are a major threat.
• Other methods for vineyards include bird scarers or noisemakers that must be rotated regularly to avoid birds getting used to them. Falcons are sometimes used to deter unwanted bird visitors.

Mammals

• Mammals in vineyards create damage, such as deer, rabbits, kangaroos, raccoons, wild boar, and baboons, reducing yield, devaluing the grapes and increasing repair costs.

Mammals Management Options

• The erection of fencing, high and buried, is a viable deterrent structure to control common, regional mammals, such as deer, rabbits, kangaroos, raccoons, wild boar and baboons.

Powdery Mildew

• Grapevine powdery mildew is caused by the fungus Erysiphe necator(Oidium tuckeri), specific to grapevines, with American species less vulnerable than V. vinifera
• As one of the most widespread vine diseases around the world, powdery mildew overwinters in buds and on canes, attacking young, green parts of the vine.
• Chardonnay and Cabernet Sauvignon are more susceptible to powdery mildew. Less prone to attack is Pinot Noir and Riesling.
• Affected parts are shown as dull showing grey or black patches that can damage young shoots, inflorescences and grapes, split fruit and create a target for infections. Thriving in shady conditions, powdery mildew requires an environment determined by temperature, specifically around 25°C (77°F)

Powdery Mildew Management Options

• Prioritize creating an open canopy that is not dense with leaves
• Apply sulfur early and often to attack spread, typically before Veraison
• Sysemtic fungisides can be effective in penetrating the green tissue of thr vine, but can cause resistance within the crop

Downy Mildew

• Downy mildew is caused by Peronospora, a water mould, and introduced from North America in the last quarter of 1800s
• Found in cooler conditions where it attacks green parts of the plant, yields are reduced as a result of defoliation, caused by rainfall and temperatures around 20°C / 68°F
• Oil spots are a great indicator of high risk periods such as warm springs and hot to stormy summers, also white fungal growth is common underside of leaves

Downy Mildew Management Options

• Treat affected vines with sprays from copper salts by using Bordeaux's mixture
• Fungicides can be used in combination with good drainage and open canopies to decrease the spread

Grey Rot

• Grey rot(Botrytis cinerea) greatly devalues fruit with loss of flavor, aroma, body, and coloring
• Seperating unharvestable fruit that are are greatly vulnerable at points of entry is important
• Flowers that affected can remain in dormant and re-emerge Spores are typically present and activated at high volumes in the periods of rainfall/ high humidity

Grey Rot Management Options

• Selecting small grape varieties with thicker skins and protecting against pests greatly reduces splitting of crop
• Canopy openings will reduce the spread, with the aid of antifungal bacterial removals for both sulfur and copper
• Apply all treatments for when flowering is nearly completed at bunch closure through Veraison

Eutypa Dieback

• Eutypa dieback or death arm greatly affects grapes in periods of high temperatures by greatly reducing yields, caused by spores that can spread through wind
• The effects commonly stem from pruning during the wrong stages so effects can be seen through shoots and leave that appear distorted

Eutypa Dieback Management Options

• Pruning and cutting trees 5-10 cm can be effective against spreading while also burning any wood material
• Bactillus Subtillus can aid in biological control
• Training or removal from the base is more efficient but commonly affects yields

Phomopsis cane and Leaf Spot

• Disease in grapes when there is a reduce amount of yields, commonly found with humidity and moderate temperatures.
• New growths and canes can whiten for develop cracks.
• Treatment can aid in combat but symptoms are prevalent.

Phomopsis cane and Leaf Spot Management options

• Apply fungiicdes regularly while also pruning bad or prune dead wood
• Improve techniques of airflows through out the crop

Esca

• Esca is an organisms that are present in warmer and drier climates.
• Commonly enters the vineyards through pruning, which causes tiger stripes.
• The results lead to the plants death in a manner of years.

Esca Management

• Research in biological agents aid in help, there are common controls though, sourcing bettering stock aid.

Pierce's Disease

• It is a disease within the sap channels in vines that originated on the American continent
• The bacterium causes shrivelling leads to a vine's death
• Symptoms tested are varied because they are unclear

Pierce's Disease Management

• Removing any plants in close proximity for vector management can aid with was ps
• Strict regulations is needed to avoid more bacteria spreading

Grape Vine Yellows

• Grapevine yellows is causes by bacteria transferred by leaffoppers
• Can be seen and transfered by disease stock
• Can be seen by delayed budburst and drooping postures

Grape Vine Yellows Management

• The focus should be vector control by the removal of host plants
• Sanitzation best practices should be enforced

Fanleaf Virus

• Fanleaf or Fanleaf Degenation, this is one of the long standing diseases known around the world
• Malformed roots and stunted growth are easily noticeable to the roots Most of the crops are greatly affected with the use of infected root stock

Fanleaf Virus Management

• The crop need to be replaced and removed at all cause
• Before replanting the area, testing should be completed

Leafroll Virus

• Affects and can lower value within a single area over time by the spread of grafting
• Reduction in root and shoot growth is common

Leafroll Virus Management

• Replacement of root stock is needed prevent infection, as they are are able to be screened
• Mealy Bugs can be used but open canopies are highly recommended to help aid the process