Pseudomonas Syringae

Bacterial Disease

Pseudomonas Syringae

Bacterial Disease

Pseudomonas Syringae

Bacterial Disease

Introduction

Angular leaf spot, caused by Pseudomonas syringae pv. lachrymans, is a bacterial disease affecting cucurbits such as cucumber, squash, melons, and pumpkins. It can cause up to 40% yield loss, making fruits unmarketable.

Favorable Conditions for Disease Development

• Temperature:
  • Optimal range: 15–25°C (best growth around 22°C).
  • Growth inhibited at higher temperatures.
• Humidity:
  • High humidity (70–80%) promotes bacterial spread and infection.
• Low Temperatures:
  • Cool, damp conditions in early spring increase disease severity.
• Plant Susceptibility:
  • High humidity + optimal temperatures = increased infection risk.

Symptoms of Angular Leaf Spot

• Leaves:
  • Small, circular spots that develop into angular, water-soaked lesions.
  • In wet weather, bacterial ooze forms, drying into a whitish crust.
  • Infected areas turn gray, shrink, and tear away, leaving irregular holes.
  • Yellow margins are seen in susceptible cultivars; resistant varieties have smaller lesions without yellowing.
• Fruit:
  • Small, superficial spots that turn white and crack open.
  • Secondary infections lead to fruit rot.
  • Severe infections cause fruit drop in young cucurbits.
• Vines & Growth Tips:
  • Indeterminate cucurbits can outgrow the infection by producing new growth.
  • Severe infections can lead to yellow, water-soaked, stunted growing tips.

Disease Management Strategies

• Cultural Practices:
  • Use disease-free seeds and resistant cultivars.
  • Avoid overhead irrigation to reduce leaf wetness.
  • Rotate crops to break bacterial survival cycles.
  • Remove and destroy infected plant debris.
• Chemical Control:
  • Copper-based bactericides can help limit spread but are most effective when applied preventively.

Conclusion

Angular leaf spot thrives in cool, humid conditions and can cause significant damage to cucurbits. Proper cultural management and timely intervention are key to minimizing its impact.