Black spot, grape anthracnose

Causal Agent: Elsinoë ampelina is a fungal pathogen that causes downy mildew in grapevines (Vitis vinifera) and related species.

Symptoms:

1. White Downy Growth:

   • Development of white to grayish downy growth on the undersides of leaves, usually visible during humid conditions.

2. Yellow Lesions:

   • Yellow lesions on the upper surfaces of leaves corresponding to the areas with downy growth underneath.

3. Reduced Photosynthesis:

   • Severe infections can lead to reduced photosynthetic activity and overall decline in plant health.

4. Fruit Infections:

   • In some cases, downy mildew can also affect grape clusters, causing lesions on berries and affecting fruit quality.

Identification:

1. Downy Growth:

   • The characteristic white to grayish downy growth on the undersides of leaves is a key identification feature.

2. Lesions on Leaves:

   • Yellow lesions on the upper leaf surface often aligning with the downy growth beneath.

Conditions Favoring Disease:

1. Humid Conditions:

   • Moisture Requirements: Downy mildews, in general, thrive in humid conditions, and their development is favored by rain or high humidity.

2. Moderate Temperatures:

   • Optimal Growth Conditions: Moderate temperatures, typically ranging from 10 to 25 degrees Celsius (50 to 77 degrees Fahrenheit), are conducive to the growth of Elsinoë ampelina.

Management:

1. Fungicides:

   • Application of fungicides, especially those effective against downy mildews, can be part of an integrated disease management strategy.

2. Cultural Practices:

   • Proper vine spacing, pruning, and canopy management to enhance air circulation can help reduce humidity and minimize disease spread.

3. Resistant Varieties:

   • Planting grapevine varieties that exhibit resistance or tolerance to downy mildew.

4. Avoiding Overhead Irrigation:

   • Minimizing water on foliage, especially through the use of drip irrigation, can reduce the risk of downy mildew.

Note: Downy mildew caused by Elsinoë ampelina can lead to significant economic losses in grape production. Integrated disease management, including the use of resistant varieties and timely fungicide applications, is crucial for effective control.