Late blight

Pathogen Overview:

• Type: Phytophthora infestans is an oomycete, a group of fungus-like microorganisms.
• Common Name: It is commonly known as the late blight pathogen.
• Hosts: Primarily affects plants in the Solanaceae family, with a significant impact on potato and tomato crops.

2. Symptoms:

• Foliar Lesions: Initial symptoms include the appearance of water-soaked lesions on leaves.
• Lesion Progression: Lesions rapidly expand, turning dark brown to black, often with a fuzzy or moldy appearance.
• Stem and Fruit Infection: In addition to leaves, stems and fruits can also be infected, leading to rotting.

3. Disease Cycle:

• Survival: The pathogen can survive in infected plant debris, tubers, or as specialized structures called oospores.
• Infection: Infection occurs through spores (sporangia and zoospores) produced on infected tissues.
• Spread: Spores are easily spread by wind, rain, or through contaminated tools, leading to new infections.
• Favorable Conditions: Wet and humid conditions, typical of cool climates, favor the development of late blight.

4. Historical Significance:

• Irish Potato Famine: Phytophthora infestans played a crucial role in the Irish Potato Famine in the mid-19th century, leading to devastating losses and significant social and economic impacts.

5. Identification:

• Lesion Appearance: Identification involves recognizing the characteristic water-soaked lesions that progress to dark, moldy spots.
• White Fungal Growth: Under humid conditions, a white, cottony fungal growth may be visible on the undersides of leaves.
• Potato Tubers: Tuber infections result in a brownish rot that can extend into the flesh.

6. Management:

• Resistant Varieties: Planting potato and tomato varieties with genetic resistance to late blight is a key management strategy.
• Fungicides: Application of fungicides, especially during periods of high disease pressure, can help control the pathogen.
• Crop Rotation: Avoiding consecutive cultivation of solanaceous crops in the same field can reduce the risk of disease recurrence.
• Sanitation: Proper disposal of infected plant debris and culling of infected tubers contribute to disease management.

7. Importance:

• Economic Impact: Late blight caused by Phytophthora infestans can result in significant economic losses due to crop damage and decreased yield.
• Global Distribution: The pathogen is widespread and can affect potato and tomato crops in various regions worldwide.