Grape: Diseases, Symptoms and their Management

April 27, 2023 no responses

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Grapes are one of the most popular fruits in the world. However, like other crops, grapes are susceptible to diseases of grape caused by fungi, bacteria, viruses, and mycoplasma. Grape cultivation is called Viticulture or Viniculture. This post will explain the important diseases of grape, their cause, symptoms and management.

Diseases of Grape

1. Anthracnose / Bird’s Eye Spot

Causal Organism: Fungus; Elsinoe ampelina

Symptoms:

Attack mainly the leaves and young shoots.
Small light brown or greyish-black lesions appear on sensitive stems, young leaves, flowers, and berries.
Affected blooms do not bear fruit.
Rain and humidity are ideal conditions for the disease’s spread.
During October and November, this disease is more prevalent.

Management:

Spraying fungicides like Bordeaux combination @ 0.8%, Copper Oxychloride @ 0.25%, or Carbendazim @ 0.1% on grapevines during the 3-4 leaf stage is effective against this disease.

2. Downy Mildew

Causal Organism: Fungus; Plasmopara viticola

Symptoms:

Light and continuous rainfall or heavy dew, combined with high humidity and low temperatures, promote disease development.
The losses are very high when the clusters are attacked before the fruit set.
Small berries that have been infected become brown and become mummified.

Management:

This disease can be treated with a Bordeaux mixture (1%), Copper Oxychloride (0.2%), Mancozeb (0.2%), Metalaxyl (0.2%), or Fosetyl Al (0.2%).

3. Powdery Mildew

Causal Organism: Fungus; Uncinula necator

Symptoms:

The disease develops under warm and dry conditions.
The disease is distinguished by the development of a white powdery (ash-like) coating on both sides of the leaves, young shoots, and immature berries.
The afflicted leaves turn pale and curl up.

Management:

Powdery mildew can be controlled easily by spraying Wettable Sulphur (1.5kg/200 litres of water).
Systemic fungicides such as Bayleton (1g/litre of water), Calaxin (3-4 ml/10 litres of water), and Benomyl (5g/10 litres of water) provide better and more sustained disease control.

4. Bacterial Leaf Spot

Causal Organism: Bacteria; Xanthomonas campestris

Symptoms:

The disease is more widespread in June-August and again in February-March.
Temperatures between 25 and 30 degrees Celsius and relative humidity levels between 80 and 90% are ideal for disease development.
On the berries, brownish-black lesions appear, which eventually become tiny and shrivelled.

Management:

Streptocycline (500 ppm) is very effective as a prophylactic spray.

5. Black Rot

Causal Organism: Fungus; Guignardia bidwellii

Symptoms:

The disease thrives in warm, damp climates with extended periods of rain and overcast weather.
The disease attacks the leaves, stem, flowers and berries.
The berries that have been impacted shrink and harden into rigid black mummies.

Management:

Spraying a Bordeaux mixture (4:4:100) on new bunches once or twice avoids infection.

6. Dead Arm

Causal Organism: Fungus; Phomopsis viticola

Symptoms:

The disease is most prevalent in South India

Management:

sprayed with Bordeaux mixture (5:5:50) followed by Difolatan (0.2%) or Daconil (0.2%) or Dithane Z-78 (0.2%) at fortnightly intervals till the canes become hard.