Late Blight in Potatoes: Symptoms, Causes and Management

• September 06 2023, by Agriplex India
• 6 min reading time

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late blight, caused by the notorious pathogen Phytophthora infestans, is one of the most destructive diseases in potato farming. It is responsible for devastating crop losses and the Irish Potato Famine in the 1840s. In this comprehensive blog, we will explore late blight in potatoes, including its symptoms, underlying causes, strategies for effective management, and answers to frequently asked questions.

Table of Contents:

1. Understanding Late Blight in Potatoes
2. Symptoms of Late Blight
3. Factors Responsible for Late Blight
4. Life Cycle of Disease
5. Effective Management Strategies
6. Frequently Asked Questions (FAQs)

1. Understanding Late Blight in Potatoes

Late blight, scientifically known as Phytophthora infestans, is a highly destructive fungal-like pathogen that primarily affects potatoes and tomatoes. It thrives in cool and wet conditions, making it a significant concern for potato farmers, especially in regions with temperate climates.

2. Symptoms of Late Blight

Recognizing the symptoms of late blight in potatoes is crucial for early detection and effective management. Here are the key indicators of late blight in potato crops:

• Water-Soaked Lesions: Small, dark-green, water-soaked lesions initially appear on the leaves, typically with a pale halo around them.

• Leaf Yellowing: As the disease progresses, the infected areas turn brown or black, and the leaves yellow, leading to rapid foliage deterioration.

• White Fungal Growth: In humid conditions, a white, cottony fungal growth may develop on the underside of infected leaves.

• Tuber Lesions: Late blight can also affect potato tubers, causing dark, firm, and irregularly shaped lesions. These lesions make the tubers inedible and unsuitable for the market.

3. Factors Responsible for Late Blight

Understanding the contributing factors can help in effectively managing late blight in potato:

• Environmental Conditions: Cool and moist conditions are ideal for late blight development. It thrives in temperatures ranging from 10°C to 20°C and is particularly problematic during periods of high humidity and frequent rainfall.

• Susceptible Potato Varieties: Some potato varieties are more susceptible to late blight than others. Choosing resistant or tolerant potato varieties can reduce the risk.

• Infected Seed Potatoes: Planting infected seed potatoes is a common source of late blight outbreaks. Ensure that your seed potatoes are certified disease-free.

• Crop Residue Management: Leftover infected plant material in the field can serve as a source of inoculum for future infections. Properly dispose of infected crop debris.

4. Life Cycle of Disease

Understanding how late blight spreads is important:

1. Overwintering: Late blight survives in infected potato remains and soil.

2. Spring Germination: It starts growing in spring when it's cool and humid.

3. Spore Production: Spores spread through wind and water.

4. Infection: Spores enter healthy potato leaves.

5. Lesion Development: Greenish-black spots grow on leaves.

6. Secondary Infections: Spores from infected leaves infect nearby plants.

7. Tuber Infection: Tubers can also get infected.

8. Continued Spread: Late blight spreads quickly in cool, wet weather.

9. Repeating the Cycle: The disease cycle continues all season.

4. Effective Management Strategies

Managing late blight in potatoes requires a proactive approach. Here are strategies to effectively control and prevent late blight outbreaks:

• Resistant Varieties: Select potato varieties known for their resistance or tolerance to late blight.

• Crop Rotation: Avoid planting potatoes in the same field consecutively. Rotate with non-host crops to break the disease cycle.

• Fungicides: When conditions are conducive to late blight development, consider using fungicides. Consult local agricultural experts for recommendations and proper application timing.

Here are the top Fungicides  for Potato Late Blight 

1) Acrobat - Acrobat Fungicide works by a combination of systemic and contact action. The active ingredients difenoconazole and mefenoxam are absorbed by the plant and move throughout the tissues, protecting within.

2) Antracol - Antracol fungicide is a highly effective and versatile crop protection solution that plays a vital role in safeguarding agricultural yields and ensuring healthy plant growth. It contains Propineb as an Active Ingredient

3) Amistar Top - Amistar Top Fungicide is a co-formulation of azoxystrobin and difenoconazole. It is used to control a variety of fungal diseases in a range of crops, including vegetables, rice, cotton, citrus, and tree nuts. It

4) Saaf - UPL Saaf is a combination of two active ingredients: carbendazim and mancozeb. Saaf works by a combination of systemic and contact action

5) Bavistin - Bavistin is a versatile fungicide that can be used for a variety of crops and contains Carbendazim 50%WP as an active ingredient

• Sanitation: Remove and destroy infected plant material promptly to prevent the disease from spreading within the field.

• Timely Irrigation: Avoid overhead irrigation, especially in the evening, to minimize leaf wetness duration.

• Monitoring: Regularly inspect your potato crop for symptoms, and if late blight is detected, take immediate action.

• Late Blight Prediction Tools: Some regions offer late blight prediction tools to help farmers time fungicide applications more effectively.

• Storage Practices: Store harvested potatoes in a cool, dry environment to prevent late blight infections on tubers.

5. Frequently Asked Questions (FAQs)

Q1: Can late blight be controlled without using chemicals? A1: While chemical fungicides are effective, you can employ organic practices like crop rotation, resistant varieties, and sanitation to reduce the risk of late blight.

Q2: Are there any early warning signs for late blight outbreaks? A2: Keep an eye on local weather forecasts, especially for cool, wet conditions. Also, monitor your crop regularly for symptoms.

Q3: Can infected potatoes be salvaged for consumption? A3: Infected potatoes are not safe for consumption. The lesions on tubers can produce toxins harmful to humans.

Q4: How long can late blight spores survive in the soil? A4: Late blight spores can persist in the soil and infect crop debris for several weeks to months, depending on environmental conditions.

Q5: What's the best way to dispose of infected plant material? A5: Burn or bury infected plant material away from potato fields to prevent further contamination.

In conclusion, late blight remains a formidable adversary for potato growers. However, with a proactive approach that includes selecting resistant varieties, employing proper sanitation, and, when necessary, judicious use of fungicides, you can protect your potato crop from this devastating disease. Remember, vigilance and timely action are your best allies in the battle against late blight.

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Agriculture Blogs Gallery Diseases Early Blight Late Blight

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