Red Rot Disease in Sugarcane and Its Management

Red Rot is one of the most destructive diseases affecting sugarcane, primarily caused by the fungus Colletotrichum falcatum (formerly known as Glomerella tucumanensis).

It can severely reduce the yield and quality of sugarcane, which is a crucial crop for sugar production, ethanol production, and other by-products in several tropical and subtropical regions around the world, including India.

The disease occurs in a wide range of sugarcane varieties, affecting both young and mature plants, and it poses a serious threat to the sugar industry in countries like India, where sugarcane is a major crop.

The symptoms of Red Rot are visible as a reddish-brown discoloration on the cane, which leads to internal rot and a significant loss of crop vigor.

Disease Condition

Red Rot is characterized by the presence of reddish or brownish lesions, which initially appear on the stem but can extend to the roots and leaves as the disease progresses.

The fungus typically enters the plant through wounds caused by physical damage, pest activity, or improper handling.

Once inside the plant, it spreads through the vascular system, affecting the cane’s ability to transport water and nutrients.

Symptoms of Red Rot Disease:

1. Wilting of Leaves: Infected plants show signs of premature yellowing and wilting of leaves.
2. Softening of Stems: The internal tissue of the cane becomes soft and spongy, turning dark brown to reddish in color. In severe cases, this leads to complete stem collapse.
3. Sugar Loss: Infected sugarcane can exhibit a significant reduction in sugar content, leading to low-quality cane that is unsuitable for processing into sugar.

Impact of Weather, Soil, and Plant Immunity on Disease Occurrence

The development and severity of Red Rot disease are heavily influenced by environmental factors such as weather conditions, soil quality, and the inherent resistance or immunity of the sugarcane plant itself.

Weather Conditions

Red Rot thrives in humid conditions, especially during the monsoon season, as the high moisture levels favor the growth and spread of the pathogen.

Warm temperatures between 20°C and 30°C are also ideal for disease development.

Extended periods of high rainfall, combined with poor field drainage, create a perfect environment for fungal infections.

Soil Conditions

Poor soil drainage and over-irrigation can contribute to increased soil moisture, which facilitates the spread of Red Rot.

Additionally, soils that are deficient in certain nutrients may weaken plant defenses, making them more susceptible to infection.

Acidic soils and soils that lack proper aeration can also exacerbate the conditions under which Colletotrichum falcatum thrives.

Plant Immunity

Some sugarcane varieties have better natural resistance to Red Rot, largely due to their ability to produce stronger cell walls and antimicrobial compounds that inhibit fungal growth.

However, many commercial sugarcane varieties are susceptible to the disease, which makes breeding for resistant varieties a key focus for researchers.

Resistance varies depending on genetic factors, with some varieties being more prone to infection than others.

Pest Management by Chemicals and Why Chemicals Are Not Always Effective

Traditionally, chemical control measures, such as fungicides, have been used to manage Red Rot disease.

Fungicides like Carbendazim and Chlorothalonil have been applied to control the spread of the fungus.

However, the effectiveness of chemical treatments has been limited, and there are several reasons for this:

Challenges with Chemical Control

1. Fungicide Resistance: Overuse of chemical fungicides can lead to the development of resistance in the pathogen, reducing the effectiveness of these treatments over time.
2. Limited Penetration: Fungicides may not penetrate the sugarcane tissues deeply enough to control infections that are already established in the plant’s vascular system.
3. Environmental and Health Concerns: The excessive use of chemicals can lead to contamination of soil and water, affecting the environment and human health. In addition, farmers may face challenges regarding the safe handling and application of these chemicals.
4. Cost Issues: Chemical treatments can be expensive, especially for smallholder farmers in developing countries, where access to high-quality fungicides may be limited.

Due to these limitations, relying solely on chemical control is not considered a sustainable solution for managing Red Rot disease in sugarcane.

Alternate Biological Solutions: Biopesticides and Their Role

Given the shortcomings of chemical control, biological solutions such as biopesticides are increasingly being explored as alternatives to manage Red Rot disease.

Biopesticides include natural organisms, such as beneficial microbes and fungi, that suppress the growth of pathogens or directly outcompete harmful fungi.

Types of Biopesticides

1. Trichoderma Species: Fungi such as Trichoderma viride and Trichoderma harzianum are widely used as biocontrol agents. They work by colonizing the plant’s root system and competing with pathogens for nutrients and space. These fungi can also produce enzymes that break down the cell walls of harmful fungi like Colletotrichum falcatum, inhibiting their growth.
2. Bacillus Species: Bacillus subtilis and Bacillus amyloliquefaciens are known for their ability to produce antimicrobial compounds that target plant pathogens.
3. Other Microbial Products: Various microbial inoculants and formulations, such as Pseudomonas fluorescens and Azospirillum brasilense, have been studied for their ability to suppress fungal growth and enhance plant immunity.

Effectiveness of Biopesticides and Microbial Products for Seed Treatment and Soil Drenching

Research has shown that biopesticides, when applied as seed treatments or soil drenches, can significantly reduce the incidence of Red Rot disease in sugarcane.

Seed Treatment

• Biopesticides such as Trichoderma or Bacillus species are applied to the seeds or seedlings before planting. These treatments form a protective barrier around the seeds, reducing the likelihood of fungal infections taking root.
• Seed treatments not only prevent initial infection but also enhance seedling growth and development, improving overall plant health and yield.

Soil Drenching

• Soil drenching with biocontrol agents involves applying microbial products directly to the soil around the roots of sugarcane plants. This helps to establish a beneficial microbial community in the rhizosphere, which competes with pathogens and prevents their spread.
• Studies have shown that soil drenching with Trichoderma or Bacillus strains significantly lowers the fungal load in the soil and can reduce the incidence of Red Rot in both the roots and stems.

Single-strain microbial products, however, have limitations in terms of their effectiveness across different environments and conditions.

Beston+ is a unique product because it uses multiple strains, making it more effective in boosting phosphorus and potassium uptake, improving the sugarcane plant’s immunity, and working across different varieties, regions, and weather or soil conditions.

In short, Beston+ provides a simple solution to a range of diseases in sugarcane, including Red Rot.

In India, where sugarcane is grown in large areas, biopesticides offer a promising solution for Red Rot management due to their environmental safety and low cost compared to chemical alternatives.

They also fit well into integrated disease management (IDM) practices that combine cultural, chemical, and biological control methods.

Conclusion

Red Rot disease remains a significant threat to sugarcane production in many countries, including India.

While chemical control methods have been used historically, their limitations highlight the need for alternative solutions.

Biopesticides and microbial products offer an eco-friendly, cost-effective, and sustainable alternative for managing Red Rot, especially when used in combination with other integrated management strategies.

Seed treatment and soil drenching with biocontrol agents like Trichoderma and Bacillus species have shown promising results in reducing disease incidence and promoting healthy plant growth.

With continued research and innovation in biocontrol technologies, it is possible to reduce reliance on chemical pesticides and create a more resilient and sustainable sugarcane industry.