RED ROT IN SUGARCANE

 

RED ROT IN SUGARCANE

(Source:https://agritech.tnau.ac.in/crop_protection/sugarcane_diseases/sugarcane_d4.html)

INTRODUCTION TO RED ROT IN SUGARCANE:

Red rot is a devastating fungal disease affecting sugarcane, caused by Colletotrichum falcatum. It poses a significant threat to sugarcane production worldwide, leading to substantial reductions in crop yield and sugar recovery. The disease was first identified in India in the late 19th century and has since spread to several other sugarcane-growing regions globally. Red rot can cause large-scale destruction in sugarcane fields if not properly managed, making it one of the most serious diseases in the sugar industry.

CAUSING ORGANISM:

    Colletotrichum falcatum.

GENERAL CHARACTERS:

·         Conidia: Cylindrical to curved, 10-20 µm long, 3-5 µm wide, colorless to light brown.

·         Appressoria: Flattened, circular to oval, 10-15 µm in diameter, usually colorless or light brown.

·         Hyphae: Filamentous, 2-5 µm in diameter, colorless to pale.

·         Mycelium: Dense mat of interconnected hyphae, colorless or pale.

BIOCHEMICAL  TEST:

·         Lactophenol Cotton Blue Staining: Blue-stained structures.

·         Germination Test: Germ tubes and appressoria formation.

·         Oxidase Test: Usually negative (no color change).

·         Catalase Test: Positive (bubbles produced).

·         Urease Test: Usually negative (no pink color).

·         Siderophore Production Test: Halo formation around colonies.

·         Growth on Different Media: Cottony or powdery colonies.

·         Cellulase Production Test: Clear halo around growth.

·         Chitinase Production Test: Clear zone around growth.

SYMPTOMES OF RED ROT:

a. External Symptoms

Externally, red rot-infected sugarcane plants display:

• Yellowing of Leaves: The leaves of affected plants begin to yellow, especially the upper ones. This may be followed by wilting and drying out.
• Discoloration and Shriveling of Stalks: The stalks take on a dull appearance and may shrink or shrivel as the disease progresses.
• Cracks in Rind: The rind of infected sugarcane stalks may crack in advanced stages, sometimes accompanied by exudation of reddish sap from the cracks.
• Dieback of Top: As the disease advances, the tops of the cane may dry out or die.

b. Internal Symptoms

Internally, the disease manifests with:

• Red Discoloration: When infected canes are split open, a distinct red discoloration is seen in the tissues, often forming alternating red and white patches, resembling a mosaic.
• Acidic Odor: An unpleasant sour smell can emanate from the infected tissues, a characteristic sign of red rot.
• Rotting of Nodes: The infection typically begins at the nodes and progresses through the internodes, resulting in rotting and breakdown of the vascular system.

DISEASE LIFE CYCLE OF RED ROT:

(Source:https://www.researchgate.net/figure/The-transmission-pathway-of-sugarcane-mosaic-disease_fig2_354679121)

Red rot is primarily spread through infected seed cane. The fungus Colletotrichum falcatum survives in plant debris and soil, where it overwinters between crop cycles. During planting, infected cuttings spread the fungus to new plants. The fungus typically enters the plant through wounds, often at the nodes, and colonizes the vascular tissue. It produces spores that are disseminated by wind, water, and even through farm machinery. The spores germinate under favorable conditions, leading to new infections in nearby plants.

EPIDEMIOLOGY AND SPREAD:

The spread of red rot occurs mainly through the use of infected seed cane and can be exacerbated by environmental factors such as humidity and rainfall. The fungus is capable of surviving in crop residues and soil for extended periods, contributing to its persistence. Secondary infection occurs when spores are transported by water, insects, or tools, infecting neighboring plants. The disease can also be spread through human activities such as improper sanitation practices, like reusing infected cuttings or using contaminated equipment.

ENVIRONMENTAL CONDITIONS FAVOURING RED ROT:

Red rot thrives in warm, humid conditions, which are typical in many sugarcane-growing regions. Optimal temperatures for the fungus range between 25°C and 30°C (77°F and 86°F). High rainfall and poor drainage in fields create favorable conditions for the disease to flourish, as excess moisture promotes fungal growth and spore dispersal. Stressed plants due to drought or nutrient deficiency are also more susceptible to red rot.

ECONOMIC IMPACT OF RED ROT:

Red rot can have a severe impact on sugarcane production, leading to significant financial losses for farmers and the sugar industry. Infected plants typically yield less sugarcane, and the quality of the juice is also compromised, reducing the overall sugar content. In severe cases, entire fields may be lost, necessitating costly replanting. Additionally, the disease increases the cost of production as farmers are forced to invest in control measures such as resistant varieties, fungicides, and sanitation practices. Losses in sugar recovery can affect the entire supply chain, from producers to sugar processors.

MANAGEMENT AND CONTROL STARATEGIES:

Cultural Practices:

• Crop Rotation: Rotate sugarcane with non-host crops to reduce fungal populations.
• Sanitation: Remove and destroy infected crop residues to prevent reinfection.
• Field Drainage: Improve drainage to reduce waterlogging, which favors fungal growth.

Seed Treatment:

• Hot Water Treatment: Immerse seed canes in hot water to kill the fungus.
• Fungicidal Treatment: Treat seed canes with fungicides to protect them from infection.

Chemical Control:

• Fungicide Sprays: Apply fungicides like Mancozeb, Carbendazim, and Chlorothalonil to control red rot infections.
• Insect Pest Management: Control insect pests to prevent entry points for the fungus.

Biological Control:

• Trichoderma Species: Use beneficial fungi like Trichoderma to compete with the red rot pathogen.

Use of Resistant Varieties:

• Resistant Varieties: Plant sugarcane varieties bred for resistance to red rot.

Integrated Disease Management (IDM):

• Combination of Strategies: Combine various control methods to achieve the most effective results.

CONCLUSION:

Red rot remains a major problem in sugarcane production worldwide. However, effective management strategies can significantly reduce its impact. Farmers can use a combination of cultural practices, chemical and biological controls, seed treatments, and resistant varieties to combat red rot. Ongoing research and breeding programs are developing new ways to fight the disease. Regular monitoring, proper sanitation, and an integrated approach to disease management are essential for maintaining healthy sugarcane crops and ensuring sustainable production.