Hazards

Question 1

Drought

Answer 1

Need min 500mm in cool and 750mm/yr in warm climates of water

Lack of water clauses stomata to close to limit water loss, which reduce photosynthesis. Growth and ripening could be impaired. Prolonged and vine could lose leaves and die.

Management Options:

Where allowed, irrigation systems should be considered as part of initial setup. Can be fitted after but harder. Some EU appelations do not allow or only in specific cases (emergencies, establishing young vines)

Drought resistant rootstocks such as V. rupestris and V. berlandieri parentage (110R and 140R).

Drought tolerant grapes like Garnacha

Question 2

Excess Water

Answer 2

Can lead to too much vegetative growth whcih can compete with grape ripening and shaded canopy

Rainfall can make canopy fungal disease prone from humidity.

Soils tat aren’t free draining can cause water logging of roots, reducing oxygen available, slowing growth and eventually killing.

Water logging can also compact soils amking them hard to work and having uncontrolled water runoff

Plant on slopes, free draining soils or construct drainage systems

Question 3

Untimely Rainfall

Answer 3

Excess during pollination and fruit set can lead to millerandage and/or coulure reducing crop size and lowering quality.

Rain in summer can reduce rate of ripening

Heavy rain close to harvest can lead to swollen grapes (reducing concentration) and to splitting which leads to gray rot.

Also makes vineyard work hard

Management: choice of site, condition of soil, choice of cover crops, drainage. Monitor weather to determine harvest.

Question 4

Freeze

Answer 4

Temps below -20C can seriously damage or kill a vine.

If grafted that is the most at risk part of the vine (if above the surface). Canes and cordons are next. Frost can kill canes, cordons, or whole vine.

Most impact in areas with strong continental climates; Canada, Washington, China

Site selection: hillsides are up to 5C warmer than valley floor. Near large or deep bodies of water benefit from moderating effect, where snow settles thickly as snow can insulate

Choice of varieties: Some are more resilient (Cab Franc, Riesling), American and Mongolian (V. amurensis) are very winter hardy. Concord can withstand up to -30C

Protecting: Build up soil around graft (hilling up), burying vines (costly and labor intensive), prune to have several trunks if one dies.

Question 5

Frost

Answer 5

Occur when cold air (0C) collect at ground level, freezing water in the vine’s growing buds and shoots. Cold winds blowing after budburst also very dangerous. If this happens to high water content plant parts it can kill them.

Two Types: Advective frosts caused by large volumes of cold air moving in from very cold areas.

Radiative frosts are result of heat being lost on still cool nights. Earth is heated by sun during the day and releases at night. That loss depends on cloud cover. Windless nights allow a layer of freezing cold air to develop just above the surface. As cold air is denser it will collect in valleys.

Reduce Risk: Site selection avoiding frost pockets and choose hillsides where cold air can drain away. Delay pruning to postpone budburst to warmer months, choosing a late budding variety, training high off the ground, bare soil b/n vines which absorb more heat during day and radiate at night.

When frost threatens: Water sprinklers (aspersion); as water freezes around plant releases latent heat protecting plant (equipment & water; only method working for advective); Wind machines pull warmer air from above to ground level (only if there is an inversion layer of warm air), helicopters; Oil or propne gas burning heaters (smudge pots) and wax candles (bougies) but high cost of labor and fuel and environment.

Question 6

Hail

Answer 6

Pellets of frozen rain that can cause serious damage.

Can rip and damage young shoots and leaves, Ripening grapes can become a point of entry for rot or other diseases

Yields can be reduced in current and future growing seasons. If early vine may be able to reshoot.

In general unpredictable though Argentina and Burgundy often.

Rockets of silver iodide in clouds to induce rain vs hail

Nets over the fruit zone. But shades so only good for high sun areas like Mendoza vs Burgundy

Have a number of spots to spread the risk

Crop insurance against hail

Question 7

Sunburn

Answer 7

Happens in prolonged hot weather and sun exposure

Grape transpiration is much more limited and therefore less effective than leaf transpiration. Hence grapes can reach higher temperatures and become burnt.

Higher risk on vines already water stressed

Leads to scars on the skin and eventually to death of the grapes

Negative impact on quality; Browing of grape, bitter taste, susceptibility to rot (skin damage); Typically remove via sorting

Row orientation can reduce (no east west orientation facing south all day); adjust direct sun through canopy management (partially shade fruit zone); Irrigation where allowed during a heat wave (reduce water stress), agricultural sunscreen spray or cloth/net shading)

Question 8

Fire

Answer 8

Serious hazard in hot and dry climates.

Climate change has seen an increase in warm weather and fires.

Australia, California, Chile

Often difficult to prvent, but vineyards near forested areas may be more at risk and provide fuel.

Cover crops and organic mulches may also be fuel, whereas bare vineyards provide less fuel.

Damage property, equipment, irrigation systems, vines, trellising

Smoke taint can be a major issu

Management: Install fire detectors and sprinklers, install a water tank, employee training

Question 9

Smoke Taint

Answer 9

Smoke in the vineyard during the growing season can result in smoky or plastic aromas in final wine.

The impact increases post veraison

The grapes absorb the smoke aroma compounds, which bind with sugars and form aroma-less precursors which become aromatic through the fermentation process.

Can increase in strength during aging as further precursors break down and become aromatic.

Management: Musts can be tested analytically or micro vinification leading up to harvest to identify extens; as precursors are on inside of skin, hand harvesting, gentle pressing, low ferentation temps, and reduced maceration can limit; flash detente and reverse osmosis can help but not entirely

or just blend

Question 10

Pests

Answer 10

Organisms that harm the vine and impact wine production negatively

Some compete for water and nutrients, while some attack the vine.

Must evaluate seriousness of attack and how to react.

Question 11

Phylloxera

Answer 11

Aphid like insect that feeds and lays eggs on vine roots.

Most commonly spread by humans (young vine roots, soil, equipment, irrigation water).

Damages roots and hence uptake of nutrients and water. Damaged roots are also susceptible to attack by bacteria and fungi. Vine weakens and eventually dies.

Symptoms: Roots are covered in insects and eggs, swelling on older roots, pale green leaf galls on underside, slow stunted shoot growth and leaf yellowing in Y3, Death in Y5

Identified in Europe in 1863 inroduced from US likely on imported vines. Destroyed 2/3 of vineyard area in late 19th century

Management: Immune on sandy soils

American species V. berlandieri, V. rupestirs, V. riparia are immune forming hard corky areas that surround eggs, seal wounds and prevent invasion by bacteria or fungi. But they smell bad. So grafting the solution

But grafting onto a single variety didn’t work in the calcareous soils of EU as they have little lime tolerance. Vines suffered from chlorosis, leaves yellowed, photo stopped, yields and quality suffered. Created hybrid rootstocks! Balance phylloxera and lime resistance

This enabled the creation of many rootstock hybrids that can deal with lots of problems. Phylloxera, nematodes, extreme soil pH, salinity, water stress, vigor control

Sig more expensive but the standard

Question 12

Nematodes

Answer 12

Microscopic worms that are very common in soil

Cause damage by feeding off roots reducing yield and vigor. Can cause slow gradual decline.

Others transmit diseases; fanleaf virus is spread by dagger nematode

Two common are dagger and root-knot. Can be already in the soil or spread by unclean nursery stock, irrigation water, vehicles.

Management: cannot be eliminated

Soil samples are taken to determine the number and type

Fumigate the soil: Chemicals in the past but now banned. Plow in mustard which contains compounds that work as biofumigants and can kil them

Best is to use a resistant root stock and ensure the plants have been heat treated to kill nematodes. Ramsey and Dog Ridge; V. champini

Question 13

Grape Moths

Answer 13

Feed on flowers and grapes

Many species have several generations per season attacking flowers in spring and grapes later.

Wounds are prone to bacterial or fungal attacks. Can result in sig crop loss.

Ligh brown apple moth in Australia; European grape vine moth in southern europe and grape berry moth in central and eastern NA.

Management: Biological controls like bacterium Bacillus thuringiensis producing substances toxic to the moths; pheremone capsules to disrupt mating (sexual confusion), natural predators (parasitic wasps, green lacewings, some spiders)

Insecticides

Question 14

Spider Mites

Answer 14

Species differ from region to region. Pacific in California, Red and Yellow in Europe

Feed on surface cells of leaves, leading to discoloration, reduction in photo, delaying ripening and reducing yields.

Thrive in dry dusty condition and are most damaging when vines are already water stressed.

Management: Use water sprinklers or cover crops / mulch to reduce dust to make it inhospitable

Ecourage predatory mites by planting host species

Pesticides may kill them. Some specific sprays for distinct species but costly

Question 15

Birds

Answer 15

Can destroy an entire crop

Isolated vineyards that are the only source of food are particularly threatened.

Eat grapes, physical damage that allows fungi and bacteria in leading to rot and disease. Starlings are one species

Management: Netting can be justified for high value like Mornington or where birds are a major threat

Bird scarers or noises but must be rotated regularly to avoid getting used to.

Falcons can be used

Question 16

Mammals

Answer 16

Eating shoots, leaves, grass, breaking grape skins and allowing fungi and bacteria to enter leading to rot, damaging trellising

Deer, rabbits, kangaroos, raccoons, boar, baboons

Fencing high and low enough

Question 17

Powdery Mildew

Answer 17

Caused by fungus Erysiphe necator also called Oidium tuckeri

Specific to grapevines with American less vulnerable. Introduced to Europe in mid 1800’s and now one of most widespread diseases in world

Chard, Cab Sauv more prone while Pinot Noir and Riesling less

Over winters in buds and canes. Attacks young green parts. Impacted parts will have dull gray patches that turn black. Can damage shoots, inflorescenses, grapes reducing yield. Grapes can split at veraison and let in other infections.

Growht rate determined by temp with optimum at 25C and thrives in shade. Doesn’t need high humidity.

Management: Open canopy to reduce shade; sulfer prevents and treats (spray after budburst up to veraison, earlier better); fungicides but can become resistant so limited usage.

Question 18

Downy Mildew

Answer 18

Mildew caused by Peronospora, a water mold that lives within vine tissue not on surface.

Introduced from NA in last part of 1800’s and now common in most wine regions.

Attacks green parts, espec young leaves and flowers reducing yields by defoliating the vine.

Grapes can also be impacted but less of a deal than defoliation

Needs rainfall and warm temps (20C) to spread. Warm springs and warm stormy summers are high risk.

Yellow circular oil spots and then white downy fungal growth on underside of leaves.

Management: Copper salt sprays (Bordeaux mixture a combo of copper sulfate and lime). This only works until 20mm of rain has fallen. Only option for organic farmers but worries about copper build in soil; Fungicides, Drainage and open canopy that dries quickly

Question 19

Gray Rot

Answer 19

Botrytis Cinerea is a fungus that can cause sig damage to fruit. Loss of yield and drop in quality (color, body, aroma / flavor).

Affected fruit needs to be selected out at harvest.

Grapes are vulnerable if there are any points of entry (grapes have rubbed against each other or punctured by birds / insects)

If flowers are impacted, the fungas can stay dormant in the grape and reemerge after veraison.

Varieties with tight bunches or think skins are most at risk. Semillon, Sauvignon Blanc, Pinot Noir and others.

Common in all wine regions. Spores are present and become active in rainfall or high humidity.

Management: small grapes with thick skins (Petit Verdot) are less susceptible, protect from pests, open canopy, remove leaves around bunches, sulfur and copper are ineffective, other fungicides can work applied at key points (when flowering is nerly complete, at end of grape formation, at bunch closure (when grapes get large enough to touch each other), and veraison.; but can develop resistance, antagonistic bacteria (Bacillus, subtilis).

Question 20

Eutypa Dieback

Answer 20

Aka dead arm is a fungal disease that leads to rotten wood and can affect whole vineyards.

Reduces yields significantly and kills vines over a 10 year period if not addressed.

Spores are spread by wind over long distances. Infection occurs through pruning wounds in moderate temperatures and especially during rain.

Affected vines display stunted shoot growth and yellow leaves. Grenache, Cab Sauv, and Sauv Blanc most susceptible. Widespread but prevalent in South Australia, south west France, California

Management: Difficult to control, late pruning and fungicide on pruning wounds; cut back impacted trunks to 5 - 10cm beyond symptom area and fungicide; burn dead wood to avoid spread; Bacillus subtilis may be effective. Remove vine and replant or retrain from a sucker (shoot at base) which is two years of lost productivity.

Question 21

Phomopsis Cane and Leaf Spot

Answer 21

Fungal disease that causes a reduction in yield.

Prevelent in years with cool wet springs followed by humidity and moderate temps. Infected canes whiten and break off easily. Shoots from these canes develop brown cracks at bases.

Grenache very; Cab Suav less

Management: fungicides 3 wks after bud burst and then every two weeks if wet conditions continue; diseased and dead wood removed during pruning and burnt, canopy management to improve air flow.

Question 22

Esca

Answer 22

Complex fungal disease caused by a group of organisms prevalant in warmer drier climates (southern europe and california).

Enters through pruning wounds. Sympoms are tiger striping of leaves, spotting inside the wood.

Reduces yield and leads to death in a few years.

Management: No chemical controls; prevention via disease free stock, less detrimental pruning techniques, not pruning in rain, removing pruning materials immeidately, disinfecting pruning wounds,. Research into Bacillus subtilis

Question 23

Pierce’s Disease

Answer 23

Bacterial disease that quickly kills vines.

Originated in Americas impacting southern USA and Central America, present in California.

Bacterium lives in the sap channels, which it clogs leading to grape shrivelling, dropping leaves, and death of the vine in one to five years.

Symptoms are unclear so vine must be lab tested. Spread by sharpshooter insect. Glassy winges sharpshooter has lead to rapid spreading from the 1980’s on. Chard and Pinot Noir more susceptible.

Management: No chemical control for bacterium; control by reducing vectors: remove vines near rivers where blue-green sharpshooter lives, insecticides, wasps that feed on eggs of sharpshooters; strict quarantine for plant movement; work is being done to develop Pierce’s disease resistant vines.

Question 24

Grapevine Yellows

Answer 24

Group of diseases caused by a type of bacteria.

Serious threat as no treatment exists. Spread by vectors including leaf hoppers and by nurseries selling untreated stock.

Most common type in Europe is flavescence doree, which spread through much of France in second half of 1900’s. No also in Germany, southern Europe, NY state and in a diff form Australia.

Delayed budburst, drooping posture because new shoots fail to become woody, and yellowing caopy (white grapes) or red (black grapes). In some strains the vine dies in others it can recover.

Bacteria can also live on cover crops. Chard and Riesling most vulneralbe. Drastically reduced yields and lower quality (high acidity and low sugar content of grapes)

Management: No control agains the bacteria, control the vector: insecticides for leafhoppers and remove plants that host them, bathe pruning wood in hot water to kill it in nurseries.

Question 25

Fanleaf Virus

Answer 25

Group of diseases (aka Fanleaf degeneration) found around the world

Early shoot growth is stunted, canes grow in distorted ways, leaves are pale, malformed and look like a fan.

Effects vary from little impact to losing most of the crop in susceptible varieties like Cab Sauv.

Spread wildly following move to grafted vines and inadvertant use of infected material. Also spread slowly by dagger nematode.

Management: No cure for disease; eventually impacted vines will need to be removed; soil tests done before planting to detect dagger; and only use virus tested planting materials.

Question 26

Leafroll Virus

Answer 26

Group of diseases present around the world.

Spread by grafting and mealy bugs (Sough Africa, Mediterranean, Argentins, California).

Doesn’t kill but reduces yield by up to half and negatively impacts quality. Slows down growth of roots and shoots. surviving fruit may take several additional weeks to ripen and have more acidity, less color and lower sugar levels. Overall health impacted as vine stores less carbohydrates.

Downward rolling of leaves in autumn and turn red (black varieties) or yellow (white).

Symptoms not always clear so must be lab tested. Some vines and rootstock carry the disease without symptoms.

Management: No cure; remove infected plants; nursery screening. Mealy bugs like humidity so open canopies can reduce; encourage natural predators (ladybugs, lacewings)