Black Rot in Table Grape Vineyards

Definition: Black rot is a common fungal disease that affects table grape vineyards. It is caused by the pathogen Guignardia bidwellii and can cause significant damage to grape crops if not managed properly.

Symptoms

Leaf Symptoms: Infected leaves develop small, dark brown to black circular lesions with yellow halos. As the disease progresses, the lesions expand and may cause defoliation.

Fruit Symptoms: Infected grapes develop small, circular, sunken lesions with dark brown to black centers. These lesions can expand and cover the entire fruit, causing it to shrivel and become mummified.

Disease Cycle

Infection: The black rot pathogen overwinters in infected plant debris, such as fallen leaves and mummified fruit. In spring, spores are released and spread by wind and rain. The spores can infect new growth, flowers, and developing fruit.

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Spread: Once a grapevine is infected, the disease can spread rapidly within the vineyard. Rain and irrigation water can splash spores from infected plant parts to healthy ones, facilitating the spread of the disease.

Secondary Infections: Secondary infections can occur throughout the growing season, leading to multiple cycles of disease development and spread.

Management Strategies

Cultural Practices:

• Prune and remove infected plant material during dormant season to reduce overwintering inoculum.
• Ensure proper spacing between vines to promote air circulation and reduce humidity, which can favor disease development.
• Practice regular canopy management, such as leaf removal, to improve airflow and reduce moisture on leaves and fruit.
• Monitor and control weeds, as they can serve as hosts for the black rot pathogen.

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Chemical Control:

• Apply fungicides according to the recommended schedule and dosage to protect healthy plant parts from infection.
• Rotate fungicides with different modes of action to prevent the development of resistant strains of the black rot pathogen.
• Follow the pre-harvest interval (PHI) guidelines to ensure the safety of grapes for consumption.

Monitoring and Early Detection:

• Regularly scout the vineyard for symptoms of black rot and other diseases.
• Monitor weather conditions, as warm and wet periods favor disease development.
• Implement a monitoring program to track disease progression and make timely management decisions.

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By implementing these management strategies, grape growers can effectively control black rot in table grape vineyards and minimize crop losses.

Keywords: disease, infected, spread, pathogen, symptoms, lesions, development, management, vineyards