Hazards, Pests and Diseases Flashcards
What is the minimum amount of rainfall needed in cool climates and warm climates?
500mm per year for cool climates and 750mm per year for warm climates.
How does a lack of water affect grape quality and yields?
Causes vine to close stomata which reduces photosynthesis as Co2 cannot enter the stomata to be used for photosynthesis. If this continues over an extended period of time- the growth of plant is impaired, grape size is reduced and ripening slows which leads to potentially unripe grapes and lower yields- even leading to vines losing their leaves and dying.
What management options can grape growers use to manage the hazard of drought?
- Where allowed consider irrigation systems as part of initial design
- If panting- consider drought resistant rootstock ( ie from V Rupestris and V. Berladieri)
- Choose a drought- tolerant variety like Grenache.
How can excess water in summer negatively affect grape quality and yields?
- Lead to too much vegetative growth which can compete with grape ripening and also shad fruit which will also result in less ripeness
- Rainfall can make the canopy prone to fungal diseases because of high humidity (potentially crop loss due to things like downy mildew).
- If soils aren’t free draining- waterlogging may occur reducing the amount of oxygen available to the roots- slowing down growth and eventually killing the vine.
How can one manage Excess of water in the vineyard?
- Planting on a slope where possible
- Planting on free-draining soil to improve drainage
- Constructing a drainage system
What is Phylloxera?
An aphid-like insect that feeds and lays eggs on roots and grapevines.
How is phylloxera spread?
Sometimes through crawling however mostly via humans on the roots of young vines, in soil, on equipment like leaf trimmers and also irrigation water.
How does Phylloxera harm vines?
By damaging the roots, reducing the uptake of nutrients and water. The damaged roots are also vulnerable to bacteria and fungi. These attacks lead at first to a weakened vine (growth and yields) and then to the death of vines.
What a symptoms of a phylloxera infestation
- 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 of the leaves
- Slow stunted shoot growth and leaf yellowing appears in around 3 years, the plant dies after around 5 years
What Management Options are there for a Phylloxera infestation of a vineyard?
- The use of American vine species rootstock hybrids and grafting vitus vinefera species vines via grafting.The species for hard, corky layers surrounding the eggs, sealing wounds and preventing invasion by cateria or fungi.
- It was noted that although especially V. berlandieri, V. riparia and V. rupestris, offer most protection- when used as single variety rootstocks they had little lime tolerance- so vines suffered from chlorosis turning the leaves yellow- halting photosynthesis and reducing yields and quality. But with rootstock hybrids- between various American species the rootstocks created to balance protection from phylloxera and resistance to lime in soil.
What Management Options are there for a Phylloxera infestation of a vineyard?
- The use of American vine species rootstock hybrids and grafting vitus vinefera species vines via grafting.The species for hard, corky layers surrounding the eggs, sealing wounds and preventing invasion by cateria or fungi.
- It was noted that although especially V. berlandieri, V. riparia and V. rupestris, offer most protection- when used as single variety rootstocks they had little lime tolerance- so vines suffered from chlorosis turning the leaves yellow- halting photosynthesis and reducing yields and quality. But with rootstock hybrids- between various American species the rootstocks created to balance protection from phylloxera and resistance to lime in soil.
- The use of rootstocks derived from American species enables the development of many rootstocks with comple parentage, that can deal with a nuber of problems- phylloxera, nematodes, extremes of soil PH, water stress, salinity and control the vigour of the vine.
- Grape growers get professional advice on the choice of rootstock and grape variety to match the appropriate rootstock to the vineyard soil, the pests to be combated and the level of vigor desired.
- Planting on woodstocks is significantly more expensive than on the vines own roots but has become the standard part of the cost of establishing a vineyard. Technically there are parts of the world where phylloxera has not entered spread yet and are still planted on their own rootstocks where one could make a calculated risk to plant on vines own roots but most don’t take this risks.
What are Nematodes and how do they damage vines?
Nematodes are microscopic worms- are very common in soils but too small to see by the naked eye. Some cause damage by feeding off the vine roots, significantly reducing yields and vigour. They can cause slow, gradual decline. Others transmit viral diseases- for example fanleaf virus is spread by the dagger nematode.
What are the main management options for nematodes?
Soil samples are taken and anylyzed in a lab to determine the number and type of nematodes present. There are unfortunately very few options to combat nematodes but they include:
- Fumigate the soil. Chemicals used to be used but these are now banned in most regions. Another method is to plough in a cover crop of mustard plans, which contain compounds that work as biofumigants, killing nematodes
- For most the best solution is the use of nematode resistant rootstocks having ensured that plants brought from nurseries have been heat treated to kill nematodes. Examples of neamtode-resistance rootstocks include Ramsey and Dog Ridge (both vitus Champini).
How do moths damage the vines? What are 2 types of grape moth?
By feeding on flowers and grapes. Many have multiple generations- attack flowers in spring and then grapes later in the year. The wounds created by the attack are then vulnerable to further attack from bacteria and fungi- including botrytis and significant crop losses can result.
The light brown apple moth in Australia,European grapevine smoth in Southern Europe and the Grape Berry Moth in central and eastern North america.
What are some management options for Grape Moths?
- Biological controls: including the bacterium Bacillus thuringiensis (which producers substances that are toxic to the moths), the use of pheromone capsules to disrupt mating (sexual confusion) and natural predators (parasitic wasps, green lacewings, some spider species)
- Insecticides can be used
What are some detrimental spider mite species? How do they damage the vine?
- pacific spider mite (destructive in california)
- Red Spider Mite and two forms of yellow spider mite ( in Europe)
They feed on the surface cells of leaves which leads to discoloration of the leaves, a reduction in photosynthesis, delayed ripening and a reduction in yields. They thrive in dusty conditions and are most damaging when vines are already water stressed.
What are the management options for Spider Mites?
- Make the environment inhospitable by the use of water sprinklers and or/cover crops or mulches 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 in the vineyard. but this can add to costs.
How do birds damage vines and what is an example of a bird species that often attack vineyards?
Birds can be a serious threat to vine growers as they eat the grapes themselves as a food source. Isolated vineyards that may be the only food source are particularly in danger of being attacked by local birds.
Starlings are a species of bird that often attack vineyards (ie in the Hilltops region as an example).
How can grape growers manage the threat of birds to vineyards?
- The cost of total netting can be justified in high value areas (for example- Mornington Peninsula in Australia) 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
How do mammals from negatively grape growing?
Mammals can do damage in vineyards by eating shoots, grapes and leaves, by breaking the skins of grapes, and thereby making them vulnerable to rot, and by damaging structures like trellising. Thus they reduce yield, low the quality and introduce extra costs in repairing the damage.
How can one manage mammals attacking the vineyard?
Fencing around the vineyard area is the main viable option to keep the mammals out of the vineyard but these have to be sufficiently high and sunk into the soil to stop burrowing animals. Some wine growers have experimented with introducing predatory birds like owls to manage smaller mammals like rodents and voles. In Margaret river kangaroos are a real threat as they can eat shoots before harvest and a lot of grapes and damage to sprinkler systems. Because kangaroos are not a threatened species they can be hunted and killed as a measure.
What is Powdery Mildew? And how does it attack vineyards?
Grapevine powdery mildew is caused by the fungus Erysiphe necator which is commonly called Oidium Tuckeri. The fungus is specific to grapevines and is one of the most widespread vine diseases around the world. Some varieties are more susceptible than others, for example Chardonnay and Cabernet Sauvignon, while Pinot Noir and Riesling are less prone to attack.
Powdery mildew overwinters (waiting or passing until winter is over) in buds and on canes. It then attacks young, green parts of the vine. Affected parts of the vine show as dull grey patches and become black patches as they advance. Patches can damage young shoots, inflorescences and grapes, reducing yield. Grapes can also split at veraison and become targets for other infections.
What are the symptoms of Downy Mildew?
Yellow circular ‘oil spots’ and then white, downy fungal growth on the underside of the leaves.
