Cercospora Leaf Spot in Pepper: A Brief Overview

Introduction:
Cercospora leaf spot is a fungal disease primarily affecting the foliage of pepper plants. Although it typically does not cause significant yield losses, it can reduce fruit size and quality. Understanding the symptoms, favorable conditions, spread, and survival mechanisms of the disease can help in effective management.

1. Symptoms:

• Circular lesions with white centers, creating a characteristic "frog-eye" appearance on leaves.

• Lesions commonly appear along the leaf mid-vein, causing blighting.

• Water-soaked and yellowing regions may develop as the disease progresses.

• Lesions can girdle stems; however, fruits are generally unaffected.

2. Favorable Conditions:

• Temperature: Optimal conditions around 23°C.

• Humidity: Relative humidity between 77-85%.

• Moisture: Prolonged rainfall, wet weather, and overhead irrigation favor disease development.

• Night Temperature: Above 16°C encourages disease spread.

• Daytime Temperature: Ideal range of 25-35°C
  

Unfavorable Conditions:

• Low Temperature: Fungal growth is limited below 5°C or above 35°C .

• Low Humidity: Disease does not develop below 90% relative humidity.

• Leaf Wetness: Infection reduces significantly if leaf wetness is less than 11 hours at temperatures below 15°C.

3. Spread and Survival:

• Spread: Fungus spreads via water, rain, wind, leaf-to-leaf contact, tools, implements, and workers.

• Survival: Survives in plant debris and on seeds.

• Inoculum Source: Primary inoculum originates from infected crop residues; the fungus can also survive on numerous weed hosts.

4. Disease Development:

• Initial Infection: Spores penetrate leaves directly, requiring water for germination.

• Lesion Progression:

  • Circular spots with light gray centers and reddish-brown margins.

  • Later turn tan with dark rings and yellowish halos, resembling a "frog-eye."

  • Affected centers dry and drop out with age.

  • Multiple spots cause yellowing, defoliation, and potential sunscald on exposed fruits.

• Stem and Petiole Infection: Spots appear oblong on stems and petioles.

5. Key Insights:

• Survival Duration: Fungus survives at least one season in infected debris.

• Moisture Dependency: Heavy dew can suffice for fungal germination.

• High-Risk Period: Warm temperatures (20-25°C) combined with excessive moisture are most conducive to disease.

Conclusion:
Effective management of Cercospora leaf spot involves monitoring environmental conditions, minimizing leaf wetness, and reducing initial inoculum through proper sanitation and crop rotation practices. Understanding the disease's lifecycle helps mitigate its impact on pepper crop yield and quality.