Wine Wednesday Quick Quiz Answers

Here are the correct answers for the Quick Quiz:

QUESTION 1 ANSWER

Which of these pests are characterised by:

‘They can transmit plant viruses and cause direct damage by feeding on vine leaves, resulting in reduced photosynthesis and grape quality’

  • Grapevine Leafhoppers
  • Grape Berry Moth
  • Spider Mites
  • Grape Phylloxera

Adult grape leafhoppers are pale yellow, with red markings on the wings. They are about 1/8 of an inch in length and somewhat wedge-shaped. Immature forms are pale green or greenish-white and lack the markings and wings of the adult. This insect becomes active about the time grape leaves are half-extended.

Adults and nymphs feed on leaves by puncturing the leaf cells and sucking out the contents. Each puncture causes a white blotch to appear on the leaf. Feeding causes leaves and fruit to appear stippled with many tiny white spots. Eventually, these spots turn brown and may cause leaves to drop prematurely. Leaves may become pale yellow in color and assume a sickly appearance. Feeding by leafhoppers may reduce the photosynthetic capacity of the plant, and the quality and quantity of the fruit may be affected. Nymphs and flying adults may be noticeable on the undersides of leaves. Some species are a vector for Pierce’s disease. Certain cultivars of grapes are more susceptible to damage from this pest than others. Wine and table grapes are generally more susceptible, particularly those that mature later in the season.

QUESTION 2 ANSWER

Which of these diseases is characterised by:

This fungal disease causes grey mould on grape clusters, leading to fruit degradation and potential loss.

  • Botrytis Bunch Rot
  • Black Rot
  • Pierce’s Disease
  • Downy Mildew

Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as ‘botrytis bunch rot’; in horticulture, it is usually called ‘grey mould’ or ‘gray mold’.

The fungus gives rise to two different kinds of infections on grapes. The first, grey rot, is the result of consistently wet or humid conditions, and typically results in the loss of the affected bunches. The second, noble rot, occurs when drier conditions follow wetter, and can result in distinctive sweet dessert wines, such as Sauternes the Aszú of Tokaji or Grasă de Cotnari. The species name Botrytis cinerea is derived from the Latin for ‘grapes like ashes’; although poetic, the ‘grapes’ refers to the bunching of the fungal spores on their conidiophores, and ‘ashes’ just refers to the greyish colour of the spores en masse. The fungus is usually referred to by its anamorph (asexual form) name, because the sexual phase is rarely observed.

QUESTION 3 ANSWER

Which of these diseases is characterised by:

A group of viruses that induce the rolling and reddening of grapevine leaves, resulting in reduced sugar accumulation in grapes

  • Leaf Roll Virus
  • Black Rot
  • Powdery Mildew
  • Pierce’s Disease

Grapevine leafroll-associated virus (GLRaV) is a name for a group of viruses that infect grapevine.

Obscure mealybugs (Pseudococcus viburni) feed on the phloem of vines and woody-stemmed plants, especially pear and apple trees and grape vines. Some individuals are vectors for infectious pathogens and can transmit them from plant to plant while feeding; mealybug-spread grapevine leafroll associated virus type III (GRLaV-3), in particular, has wreaked havoc among the grapes of New Zealand, reducing the crop yield of infected vineyards by up to 60%.

The biggest problems in Grapevine Leafroll Disease are reduced grape yield, altered grape ripening, and altered grape chemistry.: 623  Leafroll viruses are associated with rugose wood condition of grapevine.

QUESTION 4 ANSWER

Which of these diseases is characterised by:

A fungal disease that affects leaves and young shoots, causing yellowing, spotting, and reduced growth

  • Downy Mildew
  • Botrytis Bunch Rot
  • Esca
  • Leaf Roll Virus

Downy mildew refers to any of several types of oomycete microbes that are obligate parasites of plants. Downy mildews exclusively belong to the Peronosporaceae family. In commercial agriculture, they are a particular problem for growers of crucifers, grapes and vegetables that grow on vines. The prime example is Peronospora farinosa featured in NCBI-Taxonomy and HYP3. This pathogen does not produce survival structures in the northern states of the United States, and overwinters as live mildew colonies in Gulf Coast states. It progresses northward with cucurbit production each spring. Yield loss associated with downy mildew is most likely related to soft rots that occur after plant canopies collapse and sunburn occurs on fruit. Cucurbit downy mildew only affects leaves of cucurbit plants.

 

QUESTION 5 ANSWER

Which of these diseases is characterised by:

This bacterial disease is spread by certain insects and causes leaf scorching, wilting, and eventual vine death

  • Pierce’s Disease
  • Powdery Mildew
  • Spider Mites
  • European Grapevine Moth

Pierce’s disease is a bacterial disease caused by Xylella fastidiosa. This bacterium lives in the water-conducting system (xylem) of the grapevine and is spread from plant to plant by sap-feeding insects. Glassy-winged sharpshooter, an exotic plant pest is a key vector.

Xylella fastidiosa affects a wide range of plants. Symptoms are called Pierce’s disease in grapevines, leaf scorch in almonds and oleander, phony peach disease in peach, leaf scald in plum and variegated chlorosis in citrus.

The characteristic symptom of Pierce’s disease in grapevines is leaf scorch. Leaves become yellow around the leaf margins or between the veins. The outer leaf area may dry suddenly while the rest of the leaf remains green. Affected leaves are less vigorous and smaller than healthy leaves.

Leaves dry progressively over a period of days to weeks. Concentric zones of discoloured and dead tissue are seen. The whole leaf may shrivel and drop leaving only the leaf stalk attached.

Diseased stems often mature irregularly, with patches of brown and green tissue. These are known as ‘green islands’.

Flower clusters on infected vines may set berries but these usually dry up before reaching maturity.

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WEDNESDAY WINE CLUB
LEADERBOARD

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Rank
Name
Total
2 Aug
9 Aug
16 Aug
23 Aug
30 Aug
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The Team at The Wednesday Wine Club