Model Answer
0 min readIntroduction
Plant diseases pose a significant threat to global food security, causing substantial economic losses in agriculture. Sugarcane and potato are two economically important crops vulnerable to devastating diseases. Red rot, caused by a fungal pathogen, severely impacts sugarcane yield and quality. Similarly, Late blight of potato, historically responsible for the Irish Potato Famine, continues to be a major constraint in potato production worldwide. Understanding the etiology, symptoms, and effective control measures of these diseases is crucial for sustainable agricultural practices.
Red Rot of Sugarcane
Red rot is a systemic vascular wilt disease affecting sugarcane, caused by the fungus Colletotrichum falcatum. It is considered one of the most destructive diseases of sugarcane globally.
Causal Organism
Colletotrichum falcatum is an ascomycete fungus. It exists in soil and plant debris, infecting sugarcane through wounds or natural openings. Different physiological races of the fungus exist, contributing to its widespread prevalence and ability to overcome host resistance.
Disease Symptoms
- Early Symptoms: Reddish-brown discoloration of the internodes, often starting from the base of the stalk.
- Advanced Symptoms: Internal tissues become reddish-brown, extending upwards. The affected stalks become hollow and brittle.
- Leaf Symptoms: Yellowing and drying of leaves, starting from the lower ones.
- Other Symptoms: Reduced germination of setts (seed pieces), stunted growth, and reduced sugar content in the cane.
Disease Control Measures
- Use of Resistant Varieties: Employing sugarcane varieties resistant to prevalent races of C. falcatum is the most effective control measure.
- Seed Treatment: Treating setts with fungicides like carbendazim or propiconazole before planting.
- Crop Rotation: Rotating sugarcane with non-host crops can reduce the inoculum build-up in the soil.
- Sanitation: Removing and destroying infected stalks to minimize the spread of the pathogen.
- Balanced Fertilization: Providing adequate nutrition to enhance plant vigor and resistance.
- Biological Control: Utilizing bio-agents like Trichoderma species to suppress the growth of the pathogen.
Late Blight of Potato
Late blight is a devastating disease of potato and tomato, caused by the oomycete Phytophthora infestans. It gained notoriety for causing the Irish Potato Famine in the mid-19th century.
Causal Organism
Phytophthora infestans is an oomycete, often mistakenly referred to as a fungus. It thrives in cool, moist conditions and spreads rapidly through airborne spores.
Disease Symptoms
- Leaf Symptoms: Irregular, water-soaked lesions on leaves, which quickly enlarge and turn brown to black. A white, fuzzy growth (sporulation) is often visible on the underside of the leaves in humid conditions.
- Stem Symptoms: Dark brown, water-soaked lesions on stems, leading to girdling and collapse.
- Tuber Symptoms: Irregular, reddish-brown lesions on tubers, which can extend deep into the flesh. Affected tubers rot rapidly, often with a secondary bacterial infection.
Disease Control Measures
- Use of Resistant Varieties: Planting potato varieties with resistance genes to P. infestans.
- Prophylactic Fungicide Application: Applying protectant fungicides like mancozeb or copper-based fungicides before the onset of the disease.
- Systemic Fungicide Application: Using systemic fungicides like metalaxyl or dimethomorph when disease symptoms appear.
- Crop Rotation: Rotating potatoes with non-host crops.
- Proper Ventilation: Ensuring good air circulation in potato fields to reduce humidity.
- Removal of Infected Plants: Promptly removing and destroying infected plants to prevent further spread.
- Seed Potato Certification: Using certified disease-free seed potatoes.
Comparative Table: Red Rot vs. Late Blight
| Feature | Red Rot of Sugarcane | Late Blight of Potato |
|---|---|---|
| Causal Organism | Colletotrichum falcatum (Fungus) | Phytophthora infestans (Oomycete) |
| Affected Plant Parts | Stalks, leaves | Leaves, stems, tubers |
| Primary Symptoms | Reddish-brown discoloration of stalks | Water-soaked lesions on leaves and tubers |
| Favorable Conditions | Warm, humid weather | Cool, moist weather |
Conclusion
Both Red Rot of Sugarcane and Late Blight of Potato represent significant challenges to agricultural productivity. Effective disease management relies on an integrated approach combining resistant varieties, cultural practices, and judicious use of fungicides. Continuous monitoring, early detection, and prompt implementation of control measures are crucial for minimizing yield losses and ensuring sustainable production of these vital crops. Research into novel disease resistance genes and environmentally friendly control strategies remains a priority.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.