Hazards, Pests and Diseases Flashcards
Describe Freeze and explain how to manage
Hazard
Fully dormant vines are quite hardy and can tolerate winter freeze. But, if temp fall below -20 the vine can be seriously damaged or killed. If grafted onto rootstocks, the graft is the part that is most at risk (if it is above the surface of the ground). Canes and cordons are next at risk. Frost can kill canes or cordons or kill all parts of the vine above the ground, leading to the need to replace the vine.
Areas with strong continental climates are most affected; Canada, Washington State and China
Management options:
- Site selection;
Hillsides can be up to 5 degrees warmer than the valley floors.
Vineyards near large or deep bodies of water benefit from a moderating effect (for example large lakes in North America)
Vines should be planted where snow settles most thickly, as a deep layer of snow protects the vine
- Choice of varieties;
Some varieties are more resistent against winter freeze than others (cab franc / riesling)
Some American (Concord -30) and Mongolian vine species (V. amurensis) are extremely winter hardy, as are hybrids that have these species as a parent
- Protecting vines;
Building up soil around the vine graft (hilling up) is common practice in regions with cold winters, as the soil underground is only af ew degrees below freezing
Buying vines is another approach in the most extreme climates. Costly, a lot of labour every year
Vines can also be pruned to have several trunks so those killed in winter can be replaced
Describe Frost (2) and explain how to manage
Hazard
Occurs when cold air below 0 collects at ground level, freezing water in the vine’s growing buds and shoots. Cold winds blowing across the vineyard after bud burst are also very dangerous. If the freeze event happens to newly buds or young shoots that have high water content, it kills them. The damage and impact on yields can be enormous.
Cool climate areas are vulnerable though te vine respons to regular low temp by not growing until a mean air temp of 10 is reached. Warmer areas are vulnerable because the vines begin to grow and will be damaged if there is a drop in temp. if buds and young shoots are killed, the vine puts out more shoots from secondary buds, which are less fruitful and will take longer to ripen
- Advective frost, caused by large volumes of cold air moving in from very cold areas
- Radiative frost, result of heat beging lost on still, cool nights. The earth is heated by the sun during the day and releases it during the night. The amount of heat lost depends on the level of cloud cover. Windless nights will allow a layer of freezing cold air to develop just above the surface of the soil. As cold air is denser than warm air, this freezing cold air will collect in Valley bottoms.
Management options:
- Reducing the risk;
In site selection, frost pockets (places where cold air collects) must be avoided and hillside sites where cold air can drain away should be chosen
Delaying pruning postpones budburst into warmer months and choosing a variety that buds late (riesling) can help
Vines trained high of the ground offer more protection, as the coldest air is near the ground
Having bare soil between the vines absorb more heat during the day and rebates this heat during the night
- When frost threatens;
If the vineyard already has an irrigation system, water sprinklers (aspersion) can be installed. As water freezes around the parts of the plant, it releases latent heat, protecting the plant. The system must be kept on until temp rise. Cost are for the equipment and the water use. Running cost are lower than wind machines or heaters, but not if the cost of water is high.
Wind machines (4-7 m high) pull water air form above down to ground level, and raising the temp These are effective when there is an inversion layer, a warm zone of air 10 m above the ground. The investment is considerable and warranted when there is a 20% chance of a damaging reading frost in any one year. Helicopters can be used to create the same effect, it is expensive, but may be worth it if the risk is severe but short term
Heaters (smudge post) and wax candles (bougies) can be placed in vineyards and lit when there is a risk of frost. Disadvantages are the high cost of fuel and labour, low heating efficiency and contribution to air pollution
Describe Hail and explain how to mange
Hazard
Can cause damage to vines at various stages of development. Hailstones can damage and rip young shoots and leaves. Ripening grapes can also be damaged and become a point of entry for diseases, and yields can be reduced in the first and following season. If damaged is caused early in the season, the vine may be able to reshoot from existing buds. Hail is unpredictable, although in some regions in Argentina and in Burgundy they have suffered repeatedly.
Management options;
- Rockets may be fires into thunderclouds, seeding them with silver iodide to cause rainfall rather than hail
- In areas with regular hailstorm (Mendoza) some grape growers net the fruit zone of the vines to protect the ripening grapes. This creates some shading and can therefor only be used where there are high sunlight levels and is therefor more appropriate in Argentina than in Burgundy
- As hail damage can be very selective, in high risk areas growers may seek to have an number of plots in different areas to ensure continuity of production
- Growers may have to consider the additional cost of crop insurance against hail
Describe Sunburn an explain how to mange
Hazard
Vines need sunlight for photosynthesis, which enables vines to ripen grapes. But, if prolonged hot weather, sun exposed grapes can be sunburnt. Grape transpiration is much ore limited and therefore less effective than leaf transpiration. As a result, grapes can reach higher temperatures than the leas and become sunburnt. There is a higher risk on vines already in a situation of water stress.
Sunburn leas to soar on the grapes skin, and in extreme cases to the death of the grapes.
Sunburn has a negative impact on grape quality, issues are browing of there grape, a bitter taste, and increased susceptibility to rot. Therefore, sunburnt grapes typically need to be removed by sorting, which reduces yields.
Management options:
- In designing a new vineyard, row orientation and aspect can reduce the impact of the hottest afternoon sun. Example, in hot regions in the Northern-Hemisphere, east-west row orientations should be avoided so that grapes on the south side of the row are not subject do day-long sun and intense afternoon sunshine
- The amount of direct sun exposure can be adjusted through canopy management techniques. Growers may chose to partially shade there fruit zone in hot regions
- If a heatwave is forecasted, additional irrigation (if allowed) may be applied to reduce water stress and sunburn
- Special agricultural sunscreen spray can be applied or the vines can be shaded with a cloth or net
Describe Fire and explain how to manage
Hazard
Serious hazard in hot and dry countries, Australia, California and Chile have suffered in recent years
Fires may occur outside of human control and therefor are often difficult to prevent. However, vineyards near woodland, pastures or other crops may be more at riks as the provide fuel for fire. Cover crops and organic mulches can also proved fuel, whereas fire cannot spread through bare, cultivated soils.
Damage may be to property, equipment and irrigation systems, and to the vines and trellising. Smoke taint that these fires create is a major issue for the wine quality
Management options:
- Installing fire detectors and sprinklers
- Installing and maintaining a water tank
- Providing employee training for action in the event of an emergency
Describe Smoke Taint and explain how to mange
Hazard
Smoke, caused by fire, in the vineyard during the growing season can result in ‘smoky’ or ‘plastic’ aromas in the final wine, the effect on the fruit increases in the period from verasion onwards. Aroma compounds in smoke can be absorbed by the grapes.
Once in the grapes these compounds often bind with sugars and form aroma-less precursors. These compounds then only become aromatic during the fermentation process.
Management options:
- Affected must can be tested analytically and/or by micro-vilifications (to release smoke aromas) in the days leading up to harvest to establish the extent of the problem (and hence what action is needed)
- As the smoke aroma precursors are present on the inside of the skin of the grapes, how the grapes are handled can reduce the effect of smoke taint
- Hand harvesting, gently or whole bunch pressing, lower fermentation temp and reduced maceration times can reduce the uptake of the compounds
- Flash detente and reserve osmosis can also help, but will not remove the taint completely
- Winemaker may be able to reuse affected wines by blending with unaffected wines
Describe Drought and explain how to manage
Hazard
Vines need water to grow and produce good quality fruit and to produce yields that make grape growing financially viable.
Te amount of water needed is a min of 500 mm per year in cool climates and at least 750 mm in warm regions.
A lack of water causes the vine to close the stomata on their leaves in order to limit water loss. This reduces photosynthesis, if this continues, the growth of the plant slows down, grapes size is reduced and ripening slows down. Which potentially leads to unripe grapes and lower yields. If prolonged vines will lose their leaves and eventually die.
In regions that depend on irrigation, if drought continues over several years, water may become so scares that the use of water for irritations is not allowed. A a result entire vineyards can be lost (Olifants River, South Africa)
Management options:
- Where allowed, irrigations systems should be considered as part of the initial design of the vineyard. This can be fitted in later, but this can be much more difficult because of potential disruption to the vineyard fo laying pipes.
- If a vineyard is being planted, drought-resistance should be high priority. Choosing a drought resistant rootstock from V. rupestris and V. berlandieri parentage (110R and 140R) and a drought tolerant variety (Garnacha) is sternly advised
Describe Excess of Water and explain how to manage
Hazard
An excess of water in summer can lead to too much vegetative growth, which can compete with grape ripening and also mean fruit is too shaded; both leading to less ripeness.
Rainfall can also make the canopy prone to fungal diseases because of high humidity
If soils are not free draining, waterlogging may occur, reducing the amount of oxygen available to the roots, slowing down growth and eventually killing the vine.
If there is excessive rainfall on regular basis, planting on slopes or free draining soil, to improve drainage, or the construction of a drainage system should be considered before establishing the vineyard
Describe Untimely Rainfall and explain how to manage
Hazard
Excess rainfall during pollination and fruit set can lead to millerandage or coulure, reducing the size of the crop and potentially also lowering quality
Rain in mid-season can also reduce the rate of ripening fruit. Mild water deficiency before veraison reduces the growth of shoot tips, allowing the grapes to ripen mor satisfactorily
Heavy rainfall close to vintage can lead to the grapes being swollen with water (reducing concentration of must and with it the quality of the wine) and to grapes splitting, leading to grey rot. It also makes working in the vineyard very difficult, difficulty using mechanical harvesters or accessing the vineyard if on clay soils.
Management options:
- Nothing can be done about the incidence or amount of rainfall. However, issues such as choice of site (climate, slope) condition of the soil and the adequacy of drainage can mitigate some effects of untimely rainfall
- Monitoring weather forecasts; in case of forecast of heavy/prolonged rain, winemakers have to weigh up the options of early harvest with potential less-ripe fruit, or taking the chance of weather improving in time for a successful latter harvest or lossing part of all the crop.
Explain Pests
Organisms that harm the vine and impact the production of grapes in a negative way. Some compete for water or nutrients, while others directly attack the vine and/or grapes, affecting yield and quality.
Grape growers have to evaluate the seriousness of the attack and decide whether measures need to be taken. This includes an evaluation of the economic costs of actions taken in relation to the potential damage.
Describe Phylloxera (including symptoms) and explain how to manage
Pest
An aphid-like insect that feeds on and lays eggs on the roots of grape vines. It weakens vine roots and causes swellings and cracks, which ten lead to rot. This insect can spread through crawling and flying and are commonly transported by humans, for example, on the roots of young vines, in soil, on equipment such as leaf trimmers and harvesters.
Phylloxera was identified in Europe in 1863 and was accidentally introduced form the USA, probably on the roots of imported vines. Initially, phylloxera spread rapidly and destroyed two-thirds of the European vineyard in the late nineteenth century. In the 19th century it was noted that vineyards on sandy soil were immune to phylloxera.
The symptoms are:
- Vines die of drought in patches that increase in size year by year
- Vine roots are covered with the insects surrounded by yellow eggs
- Swellings on older roots
- Pale green leaf galls on the under-surface to he leaves
- Slow, stunted shoot growth and leaf yellowing appears around three years, the plant dies after around five years
Management option:
- The use of American vine species proved to be the way ahead (V. berlandieri, V. riparian and V. rupestris offer most protection). These species form hard, corky layers that surround the eggs, sealing the wounds and preventing invasion by bacteria or fungi. However, planting these vines led to different and undesirable aromas in the resulting wines. The solution was to graft European varieties onto American rootstocks. However, grafting onto the rootstocks of single American varieties causes problems in the typically calcareous soils of Europe as these varieties have little lime tolerance. The vines sufferd from chlorides turning the leaves yellow, halting photosynthesis and reducing yields and quality. The solution was to create rootstocks hybrids between the various American species in order to balance the level of protection to Phylloxera and resistance to lime in the soil
- The use of rootstocks derived form American species enabled the development of many rootstocks, often with complex parentage, that can deal with a number of problems - Phylloxera, nematodes, extremes of soil pH, water stress, salinity - and control the vigour of the vine
Planting on rootstocks is significantly more expensive than on the vines own roots, but has become a standard part of the costs of establishing a vineyard
Describe Nematodes and explain how to manage
Pest
Tiny worms, very common in soils, that are usually too small to be seen by the naked eye. Some cause damage by feeding off vine roots, significantly reducing yields and vigour. The can cause slow, gradual decline. Other transmit viral diseases, for example fan leaf virus is spread by the dagger nematode
Two of the most commonly occurring are the root-knot nematode and the dagger nematode. Nematodes are either present in the soil or spread by unclean nursery stocks, irrigation of water or vehicles. Once present, the can only be managed, not eliminated.
Management options:
Soil samples are taken and analyzed in laboratory to determine the number and type of nematode present.
- Leave the soil fallow for a number of years, very expensive as no crop is produced
- Fumigate the soil, chemicals used to be used, but hese are now banned in most regions. Another method is to plough in a cover crop of mustard plant, which contains compounds that work as bio-fumigants, killing nematodes.
- For most, the best solution is the use of nematode-resistant rootstocks
Describe Grape Moths and explain how to manage
Pest
A number of different moths damage the vines by feeding on the flowers and the grapes. May species have several generations per season, attacking flowers in spring and grapes later in the year. The wounds created are then vulnerable to further attacks from bacteria and fungal diseases, including botrytis, which can lead to significant crop losses.
The most common are the light brown apple moth in Australia and the European grapevine moth is southern Europe and the grape berry moth in central and eastern North America.
Management options:
- Biological controls; the Bacillus thuringiensis (produces substance that is toxic to moths), use of pheromone capsules to disrupt mating (sexual confusion) or natural predators (parasitic was, green lacewings or some spider species)
- Insecticides can also be used
Describe Spider Mites and explain how to manage
Pest
The species of spider mites differs from region to region. The Pacific spider is the most destructive in California, while in Europe the red spider and two forms of yellow spider mites can cause damage.
The feed on the surface cells of leaves, leading to discoloration of the leaves, reduction in photosynthesis, delaying ripening and a reduction in yield. They thrive in dusty conditions an are most damaging when vines are already water stressed.
Management options:
- Make the environment inhospitable by the use of water sprinklers and/or cover crops or mucked to reduce dust
- Encourage predatory mites (by planting host species) 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, this can add to costs.
Describe Birds and how to manage
Pest
Birds can ba serious threat to vine growers as they destroy an entire crop of grapes as they ripen. Isolated vineyards that provide the only source of food in an area are particularly in danger. in addition to physical damage to the grapes, bird damage allows bacteria and fungi to enter bunches, which leads to rot. Starling are one species that often attack vineyards
Management options:
- The cost of tall netting can be justified in high value areas (Mornington Peninsula) or where birds are a major threat
- Other measures such as bird scarers or noises can be used, but must be rotated regularly to avoid the birds getting used to them. Falcons are sometimes used to deter unwanted bird visitors
