WSET Diploma D1 Exercises (Hazards, Pests and Diseases: part 2)

Answer

Phylloxera infests vine roots, feeding on them and causing direct damage. This weakens the vine’s ability to absorb water and nutrients, making it more susceptible to secondary infections, which leads to reduced vigor and, ultimately, vine death.

The most effective solution is to use American vine species as rootstocks. These species develop hard, corky layers around phylloxera eggs, sealing wounds and preventing bacterial or fungal infections. To protect against phylloxera, Vitis vinifera is grafted onto these resistant rootstocks.

Another effective approach is planting on sandy soils, as phylloxera struggles to survive in such conditions, reducing its impact and limiting vine damage.

Grading Criteria

• Impact
  • For pointing out that phylloxera infests vine roots, you get 1 point.
  • For explaining that phylloxera feeds on vine roots and causes direct damage, you get 1 point.
  • For explaining that this weakens the vine’s ability to absorb water and nutrients, you get 1 point.
  • For explaining that this makes the vine vulnerable to secondary infections, you get 1 point.
  • For concluding that this leads to reduced vigor and, ultimately, vine death, you get 1 point.
• How to manage
  • For identifying the use of American vine species as rootstocks as the most effective solution, you get 1 point.
  • For explaining that American vine species develop hard, corky layers around phylloxera eggs, you get 1 point.
  • For explaining that this seals wounds and prevents bacterial or fungal infections, you get 1 point.
  • For explaining the grafting method, in which Vitis vinifera is grafted onto these resistant rootstocks, you get 1 point.
  • For identifying planting on sandy soils as another option, you get 1 point.
  • For explaining that phylloxera struggles to survive in such conditions, reducing its impact and limiting vine damage, you get 1 point.

Answer

Birds and mammals directly damage shoots, leaves, and grapes, creating entry points for bacteria and fungi, which can lead to fruit rot and reduced yields. Isolated vineyards are especially at risk, as they may be the only available food source in the area.

To protect vineyards from birds, growers often install netting, particularly in high-value regions or areas with severe bird pressure. Other methods include bird scarers and sound devices, but these must be rotated regularly to remain effective. Additionally, falcons can be used as a natural deterrent.

For mammals, high fences are the most effective protection.

Grading Criteria

• Impact
  • For pointing out that birds and mammals directly damage shoots, leaves, and grapes, you get 1 point.
  • For explaining that this creates entry points for bacteria and fungi, you get 1 point.
  • For concluding that this leads to fruit rot and reduced yields, you get 1 point.
  • For pointing out that isolated vineyards are especially at risk, you get 1 point.
• How to manage
  • For birds
    • For identifying installing netting, bird scarers, sound devices, falcons as a protecting option from birds, you get 1 point each, for a total 4 points.
    • For explaining that bird scarers, sound devices must be rotated regularly to remain effective, you get 1 point.
  • For mammals
    • For identifying high fences as a protecting option from mammals, you get 1 point.

Answer

Powdery mildew, caused by Erysiphe necator, is a fungal disease that appears as dull gray patches on leaves, which darken as the infection progresses. It can damage young shoots, inflorescences, and grapes, causing berries to split at véraison, making them more susceptible to other infections. This disease reduces yield, accelerates sugar accumulation while slowing the ripening of tannins and aromas, and raises pH levels, potentially leading to winemaking challenges.

To manage powdery mildew, grape growers typically maintain an open canopy to improve airflow and reduce leaf density. Sulfur sprays are commonly applied from a few weeks after budburst until véraison. Systemic fungicides can also be used, but their application should be limited to prevent resistance development.

Grading Criteria

• What powdery mildew is
  • For pointing out that powdery mildew is a fungal disease, you get 1 point.
  • For pointing out that powdery mildew is caused by Erysiphe necator, you get 1 point.
  • For explaining that powdery mildew appears as dull gray patches on leaves, which darken as the infection progresses, you get 1 point.
• Impact
  • For pointing out that this can damage young shoots, inflorescences, and grapes, you get 1 point.
  • For explaining that this causes berries to split at véraison, you get 1 point.
  • For explaining that this makes them more susceptible to other infections, you get 1 point.
  • For concluding that this disease reduces yield, accelerates sugar accumulation, slowing the ripening of tannins and aromas, and raises pH levels, you get 1 point each, for a total 4 points.
• How to manage
  • For identifying maintaining an open canopy as a management option, you get 1 point.
  • For explaining that this improves airflow and reduces leaf density, you get 1 point.
  • For identifying sulfur sprays as a management option, you get 1 point.
  • For explaining that these are commonly applied from a few weeks after budburst until véraison, you get 1 point.
  • For identifying systemic fungicides as a management option, you get 1 point.
  • For explaining that their application should be limited to prevent resistance development, you get 1 point.

Answer

Downy mildew, caused by Peronospora, is a fungal disease that appears as white, downy growth on the underside of leaves and yellow, circular “oil spots” on the surface. If left unchecked, it leads to defoliation, which can drastically reduce yields. While downy mildew can also affect grapes, the primary concern is the loss of foliage.

To manage the disease, grape growers commonly use copper-based sprays, such as Bordeaux mixture, though their effectiveness diminishes after 20mm of rainfall. Other fungicides may be applied as needed. Additionally, ensuring good drainage and maintaining an open canopy to improve air circulation and reduce humidity are key preventive measures.

Grading Criteria

• What downymildew is
  • For pointing out that downy mildew is a fungal disease, you get 1 point.
  • For pointing out that downy mildew is caused by Peronospora, you get 1 point.
  • For explaining that downy mildew appears as white, downy growth on the underside of leaves and yellow, circular “oil spots” on the surface, you get 1 point.
• Impact
  • For pointing out that this leads to defoliation, you get 1 point.
  • For explaining that this defoliation drastically reduces yields, you get 1 point.
  • For explaining that the impact on grapes is limited, you get 1 point.
• How to manage
  • For identifying the use of copper-based sprays as a management option, you get 1 point.
  • For pointing out that these copper-based sprays are called Bordeaux mixture, you get 1 point.
  • For explaining that their effectiveness diminishes after 20mm of rainfall, you get 1 point.
  • For identifying the use of other fungicides as a management option, you get 1 point.
  • For identifying ensuring good drainage and maintaining an open canopy as a management option, you get 1 point.
  • For explaining that this improves air circulation and reduces humidity, you get 1 point.

Answer

Gray rot, caused by Botrytis cinerea, is a fungal disease that appears as gray mold on grapes, often causing them to shrivel or split, making them more vulnerable to secondary infections. It reduces both yield and wine quality. If the fungus infects flowers, it can remain dormant and reappear after véraison.

To manage gray rot, grape growers can select resistant grape varieties with thick skins. Protecting grapes from pests is also crucial to prevent skin damage. Preventive measures include maintaining an open canopy and removing leaves around grape clusters to improve airflow. Fungicides are typically applied at key stages: the end of flowering, grape formation, bunch closure, and véraison. Additionally, biological control methods, such as Bacillus subtilis, are being explored as alternative treatments.

Grading Criteria

• What gray rot is
  • For pointing out that gray rot is a fungal disease, you get 1 point.
  • For pointing out that gray rot is caused by Botrytis cinerea, you get 1 point.
  • For explaining that gray rot appears as gray mold on grapes, you get 1 point.
• Impact
  • For pointing out that this causes grapes to shrivel or split, you get 1 point.
  • For explaining that this makes them more vulnerable to secondary infections, you get 1 point.
  • For explaining that this reduces both yield and wine quality, you get 1 point.
  • For concluding that if the fungus infects flowers, it can remain dormant and reappear after véraison, you get 1 point.
• How to manage
  • For identifying the selection of resistant grape varieties as a management option, you get 1 point.
  • For explaining that resistant grape varieties usually have thick skins, you get 1 point.
  • For identifying the protection of grapes from pests as a management option, you get 1 point.
  • For explaining that this prevents skin damage, which can lead to gray rot infection, you get 1 point.
  • For identifying the maintenance of an open canopy and the removal of leaves around grape clusters as a management option, you get 1 point.
  • For explaining that this improves airflow, you get 1 point.
  • For identifying the application of fungicides as a management option, you get 1 point.
  • For explaining that fungicides are applied at the end of flowering, grape formation, bunch closure, and véraison, you get 1 point.
  • For identifying biological control methods, such as Bacillus subtilis, as a management option, you get 1 point.

Answer

Eutypa dieback, caused by Eutypa lata, is a fungal disease that stunts shoot growth and causes leaves to turn yellow in spring. The infection leads to wood rot, resulting in dead or weakened vine arms and significant yield reduction. If left untreated, the disease can kill vines over a 10-year period and spread throughout the vineyard via airborne spores.

To manage Eutypa dieback, growers prune late in the season and apply fungicide to pruning wounds. In severe cases, they may retrain the vine from a sucker or remove and replant it entirely. Cutting back infected trunks 5–10 cm beyond visible symptoms and treating the wounds with fungicide is also an effective strategy. Finally, burning dead wood helps prevent the spread of spores. In some cases, biological controls are also used.

Grading Criteria

• What Eutypa dieback is
  • For identifying Eutypa dieback as a fungal disease, you get 1 point.
  • For stating that Eutypa dieback is caused by Eutypa lata, you get 1 point.
  • For explaining that Eutypa dieback stunts shoot growth, you get 1 point.
  • For explaining that Eutypa causes leaves to turn yellow in spring, you get 1 point.
• Impact
  • For identifying that Eutypa dieback leads to wood rot, you get 1 point.
  • For explaining that this results in dead or weakened vine arms, you get 1 point.
  • For explaining that this leads to significant yield reduction, you get 1 point.
  • For pointing out that if left untreated, the disease can kill vines over a 10-year period, you get 1 point.
  • For stating that it spreads throughout the vineyard via airborne spores, you get 1 point.
• How to manage
  • For identifying late-season pruning as a management strategy, you get 1 point.
  • For recognizing the application of fungicide to pruning wounds as a management method, you get 1 point.
  • For explaining that in severe cases, vines may be retrained from a sucker or completely removed and replanted, you get 1 point.
  • For identifying the practice of cutting back infected trunks 5–10 cm beyond visible symptoms, you get 1 point.
  • For explaining that pruning wounds should be treated with fungicide, you get 1 point.
  • For stating that burning dead wood helps prevent the spread of spores, you get 1 point.
  • For noting that biological controls are also used, you get 1 point.

Answer

Phomopsis cane and leaf spot, caused by Phomopsis viticola, is a fungal disease that leads to whitening and brittleness of infected canes, making them prone to breaking. Affected shoots develop brown cracks at their bases, and the leaves also show signs of infection. Over time, the disease weakens vines, reduces yields, and compromises overall vine health.

To manage Phomopsis cane and leaf spot, growers apply fungicides three weeks after budburst and continue every two weeks if wet conditions persist. Pruning to remove diseased and dead wood, followed by burning or burying the cuttings, is an effective control method. Additionally, proper canopy management improves airflow and reduces humidity, helping to prevent the spread of the disease.

Grading Criteria

• What Phomopsis cane and leaf spot is
  • For identifying Phomopsis cane and leaf spot as a fungal disease, you get 1 point.
  • For stating that it is caused by Phomopsis viticola, you get 1 point.
  • For explaining that the disease causes infected canes to whiten and become brittle, making them prone to breaking, you get 1 point.
  • For explaining that affected shoots develop brown cracks at their bases, you get 1 point.
  • For explaining that the disease also causes visible symptoms on leaves, you get 1 point.
• Impact
  • For identifying that Phomopsis cane and leaf spot weakens vines over time, you get 1 point.
  • For explaining that this results in reduced yields, you get 1 point.
  • For explaining that it compromises overall vine health, you get 1 point.
• How to manage
  • For identifying the application of fungicides three weeks after budburst as a management strategy, you get 1 point.
  • For explaining that fungicide applications should continue every two weeks if wet conditions persist, you get 1 point.
  • For identifying pruning to remove diseased and dead wood as a management method, you get 1 point.
  • For explaining that pruning cuttings should be burned or buried to prevent further infection, you get 1 point.
  • For identifying proper canopy management as a preventive measure, you get 1 point.
  • For explaining that improved airflow and reduced humidity help prevent the spread of the disease, you get 1 point.

Answer

Esca, caused by multiple fungi, is a fungal disease characterized by tiger-striping on leaves and dark spots inside the wood. It reduces yield and can kill vines within a few years.

There is no chemical control available, so prevention is the primary management strategy. One key approach is using disease-free planting stock. Implementing less damaging pruning techniques is also crucial, including avoiding pruning in the rain, promptly removing prunings from the vineyard, and disinfecting pruning wounds. Research on biological control agents is ongoing.

Grading Criteria

• What Esca is
  • For identifying Esca as a fungal disease, you get 1 point.
  • For stating that Esca is caused by multiple fungi, you get 1 point.
  • For explaining that the disease is characterized by tiger-striping on leaves, you get 1 point.
  • For explaining that Esca causes dark spots inside the wood, you get 1 point.
• Impact
  • For identifying that Esca reduces yield, you get 1 point.
  • For explaining that the disease can kill vines within a few years, you get 1 point.
• How to manage
  • For identifying that there is no chemical control available, you get 1 point.
  • For pointing out that making prevention the primary management strategy, you get 1 point.
  • For recognizing the use of disease-free planting stock as a preventive measure, you get 1 point.
  • For identifying the importance of less damaging pruning techniques, you get 1 point.
  • For explaining that avoiding pruning in the rain helps prevent infection, you get 1 point.
  • For explaining that promptly removing prunings from the vineyard is an effective management practice, you get 1 point.
  • For explaining that disinfecting pruning wounds helps reduce the risk of infection, you get 1 point.
  • For noting that research on biological control agents is ongoing, you get 1 point.

Answer

Pierce’s disease is caused by the bacterium Xylella fastidiosa and spread by sharpshooter insects. When a vine becomes infected, its sap channels become clogged, leading to leaf drop and grape shriveling. Eventually, the vine dies.

There is no known cure. To manage the disease, grape growers can reduce the sharpshooter population by removing vines near rivers, which serve as a habitat for blue-green sharpshooters, applying chemical insecticides, and introducing parasitic wasps that prey on sharpshooter eggs. Strict quarantine measures are also essential to prevent the disease from spreading.

Grading Criteria

• What pierce’s disease is
  • For pointing out that Pierce’s disease is a bacterial disease, you get 1 point.
  • For pointing out that Pierce’s disease is caused by Xylella fastidiosa, you get 1 point.
  • For pointing out that Pierce’s disease is spread by sharpshooter insects, you get 1 point.
• Impact
  • For pointing out that the vine’s sap channels become clogged, you get 1 point.
  • For explaining that this leads to leaf drop and grape shriveling, you get 1 point.
  • For explaining that the vine eventually dies, you get 1 point.
• How to manage
  • For explaining that there is no known cure, you get 1 point.
  • For identifying reducing the sharpshooter population as a protective measure, you get 1 point.
  • For explaining that the sharpshooter population is reduced by removing vines near rivers, you get 1 point.
  • For explaining that rivers serve as a habitat for blue-green sharpshooters, you get 1 point.
  • For identifying applying chemical insecticides and introducing parasitic wasps that prey on sharpshooter eggs as management options, you get 1 point each, for a total of 2 points.
  • For identifying strict quarantine as a management option, you get 1 point.

Answer

Grapevine yellows is a bacterial disease caused by Phytoplasma and spread by leafhoppers. It delays budburst, causes shoots to droop, and turns the canopy yellow or red, depending on the grape variety. The disease significantly reduces yields and lowers grape quality by limiting sugar accumulation and increasing acidity. Some strains can even lead to vine death.

There is no known cure, but growers can manage the disease by controlling leafhopper populations through insecticide applications, removing host plants (including certain cover crops), and following best nursery practices. One effective method is hot water treatment, where pruning wood is bathed in hot water to eliminate the bacteria.

Grading Criteria

• What grapevine yellows is
  • For pointing out that grapevine yellows is a bacterial disease, you get 1 point.
  • For pointing out that grapevine yellows is caused by Phytoplasma, you get 1 point.
  • For pointing out that grapevine yellows is spread by leafhoppers, you get 1 point.
• Impact
  • For pointing out that it delays budburst, causes shoots to droop, and turns the canopy yellow or red, you get 1 point each, for a total of 3 points.
  • For explaining that this reduces yields and lowers grape quality, you get 1 point.
  • For explaining that the decline in grape quality is primarily due to limited sugar accumulation and increased acidity, you get 1 point.
  • For explaining that some strains can even lead to vine death, you get 1 point.
• How to manage
  • For explaining that there is no known cure, you get 1 point.
  • For identifying controlling leafhopper populations as a protective measure, you get 1 point.
  • For identifying insecticide applications, removing host plants, and following best nursery practices as options for controlling leafhopper populations, you get 1 point each, for a total of 3 points.
  • For identifying hot water treatment as a protective measure, you get 1 point.
  • For explaining that hot water treatment involves bathing pruning wood in hot water to eliminate bacteria, you get 1 point.

Answer

Leafroll virus is caused by the Grapevine Leafroll-associated Virus spread by grafting and by mealy bugs. It leads to the downward rolling of leaves in autumn, turning the leaves of black grape varieties red and those of white grape varieties yellow. The virus also slows root and shoot growth, significantly reducing yields by up to 50%. Infected vines store less carbohydrate, which weakens overall vine health and delays ripening. Grapes affected by leafroll virus tend to have higher acidity, lower sugar levels, and reduced color intensity.

There is no known cure. To manage the disease, grape growers should remove and replace infected vines with virus-free stock, while nurseries should screen vines for infections. The most common protective measure is controlling mealybugs, the primary virus vector, by maintaining an open canopy to reduce humidity and encouraging natural predators.

Grading Criteria

• What leafroll virus is
  • For pointing out that leafroll virus is a viral disease, you get 1 point.
  • For pointing out that leafroll virus is caused by Grapevine Leafroll-associated Virus, you get 1 point.
  • For explaining that leafroll virus is spread through grafting and by mealybugs, you get 1 point.
• Impact
  • For pointing out that it causes the downward rolling of leaves in autumn, you get 1 point.
  • For explaining that this turns the leaves of black grape varieties red and those of white grape varieties yellow, you get 1 point.
  • For pointing out that this slows root and shoot growth, you get 1 point.
  • For explaining that this reduces yields by up to 50%, you get 1 point.
  • For pointing out that infected vines store less carbohydrate, you get 1 point.
  • For explaining that this weakens overall vine health and delays ripening, you get 1 point.
  • For pointing out that grapes affected by leafroll virus tend to have higher acidity, lower sugar levels, and reduced color intensity, you get 1 point.
• How to manage
  • For explaining that there is no known cure, you get 1 point.
  • For identifying removing and replacing infected vines with virus-free stock, controlling mealybugs, and maintaining an open canopy, and encourages natural predators as protective measures, you get 1 point each, for a total of 4 points.
  • For explaining that an open canopy reduces humidity, you get 1 point.