Horticulture

Mango Root Rot and Damping-off Disease Management: Symptoms, Treatment, Chemical, Biological, and Organic Control

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The Mango Root Rot & Damping-off Disease caused by the fungus Rhizoctonia solani is a significant problem in mango cultivation worldwide. The disease affects mango plants of all ages, causing severe damage to the root system, reducing growth, and even causing the death of the plant. Rhizoctonia solani can also cause damping-off disease in seedlings, leading to the rotting of the stem at the soil line and the death of the plant.

Mango Root Rot and Damping-off Disease Management

The disease can be challenging to control, and prevention is key to minimizing the risk of infection. This disease can be spread through the soil, infected plant debris, and contaminated tools, making it essential to adopt integrated disease management strategies to control its spread. Effective management of Mango Root Rot and Damping-off Disease is critical to maintaining the productivity and sustainability of mango orchards.

To effectively manage this disease, it is important to understand its disease cycle, the mode of disease spread, and the best methods for controlling it. This article will provide an overview and discussion of the Mango Root Rot & Damping-off Disease in Mango crops, including its symptoms, identification techniques, and control.

Mango Root Rot and Damping-off Disease Management

The Causal Organism of Mango Root Rot & Damping-off Disease

  • Rhizoctonia solani is a filamentous, soil-borne fungus that belongs to the Family Ceratobasidiaceae of Order Cantharellales of the Phylum Basidiomycota.
  • The mycelium is white to light brown and can grow several centimeters long. The hyphae are septate, which helps the fungus grow and spread rapidly.
  • The fungus also produces sclerotia, dark, rigid structures that can persist in the soil for several years, even without a host plant.
  • The fungus reproduces by producing small, round spores called conidia on conidiophores, which emerge from the mycelium and are released into the soil and can infect nearby plants.
  • The fungus has a characteristic “shoestring” appearance, with long, thin hyphae that resemble shoelaces.

The Disease Cycle of Mango Root Rot & Damping-off Disease

The disease cycle of the Mango Root Rot & Damping-off Disease, Rhizoctonia solani, in Mango Crops starts as the sclerotia, which are hard, dark structures that can persist in the soil, infected plant debris or on tools used in the field. It can infect mango plants at any growth stage, from seedlings to mature trees. The fungus infects the plant’s roots, often through wounds or cracks in the bark.

Once inside the plant, the fungus colonizes the root system, causing root rot and damping off, which results in the death of the plant. The fungus produces enzymes that break down the plant tissues, which provide nutrients for the fungus to grow and spread. The fungus hyphae spread through the soil and can infect nearby plants.

The pathogen reproduces by producing small, round spores called conidia, which are released into the soil and can infect nearby plants. The spores are produced on short stalks, called conidiophores, which emerge from the mycelium. The fungus can also reproduce by producing fruiting bodies called sclerotia, which contain masses of hyphae and can remain dormant in the soil until favorable conditions occur.

Occurrence of Mango Root Rot & Damping-off Disease in Mango Crop

  • Location of Mango Root Rot & Damping-off disease: This disease occurs in mango crops in India, Africa, Bangladesh, Sri Lanka, Thailand, Indonesia, Vietnam, the Philippines, the United States, Mexico, Brazil, Colombia, Peru, and Australia.
  • Host range: The most common crops affected by Rhizoctonia solani are mango, beans, rice, potato, cotton, sugar beet, peanuts, soybeans, and tomatoes.

Favorable Conditions for Mango Root Rot & Damping-off Disease Spread in the Field

  • Environmental factors such as high humidity, cloudy atmosphere, and high soil moisture can contribute to the development of this disease.
  • It thrives in warm soil conditions, with temperatures between 20-25°C. When the soil temperature is below 18°C or above 30°C, the fungus may not grow or cause damage.
  • Excess soil moisture caused by overwatering, heavy rainfall, or poorly drained soils creates an ideal environment for the fungus to grow.
  • The pathogen prefers slightly acidic to neutral soils with pH 5.5-7. Soils that are too acidic or alkaline may not be suitable for the fungus.
  • It can persist on crop residues in the soil for several years, a source of infection for subsequent crops.
  • Soil compaction reduces soil aeration and drainage, creating an environment conducive to the pathogen’s growth and spread.
  • Nutrient deficiencies, especially phosphorus, can make the plants more susceptible to Mango Root Rot and Damping-off Disease.

Damage Symptoms of Mango Root Rot & Damping-off Disease

  • The disease is characterized by sudden defoliation after the seedlings emerge from the soil.
  • In seedlings, the first symptom is damping-off, which results in the rotting of the stem at the soil line, leading to the death of the plant.
  • In prolonged wet weather conditions, the pathogen infects the crop beneath the ground level in circular patches. These patches grow and show girdling effects at the base of the seedlings.
  • In mature trees, the first symptoms are usually observed in the root system, with a reduction in root growth and the appearance of blackened roots.
  • Infected trees may also show stunted growth, wilting, and yellowing of leaves, reducing fruit yield and quality.

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Mango Flowers

Percentage of Yield Loss Due to Mango Root Rot & Damping-Off Disease in Mango Crop

  • The disease can cause 2-10% yield losses in the United States. In Mexico, yield losses are 15-30%. In India, the yield losses are 10-50%. In Bangladesh, the losses are 20-30%. In Sri Lanka, the losses are 10-30%. In China, a 5-10% yield loss is seen.
  • In Africa, yield losses are 10-50%. In the Philippines, it is 30%. In Thailand, it is 40%. In Brazil, it is 50%. In Australia, the losses are 5-30%. The Economic Threshold Level is determined at 10-20% of the affected crop.

Cultural Control Measures of Mango Root Rot & Damping-Off Disease

  • Planting disease-free mango seedlings is an essential cultural control measure to prevent the spread of the disease.
  • Pruning is an important cultural practice that can improve tree vigor, reduce shading, and increase fruit quality. Pruning tools should be disinfected between cuts to prevent the spread of the disease.
  • Proper sanitation practices like removing and destroying diseased plant material and pruning mango trees to improve air circulation.
  • Proper fertilization management can help improve the vigor and health of the mango trees, making them less susceptible to Mango Root Rot and Damping-off Disease.
  • Rhizoctonia solani thrives in poorly drained soils. So avoid planting mango trees in low-lying areas prone to waterlogging, and ensure the soil has proper drainage.

Biological Control Measures of Mango Root Rot & Damping-Off Disease

  • Trichoderma spp., Bacillus spp., and Pseudomonas fluorescens work by colonizing the mango root zone and competing with Rhizoctonia solani for nutrients and space.
  • Mycorrhizal fungi can form a symbiotic relationship with mango roots, increasing their disease resistance and improving nutrient uptake.

Chemical Control Measures of Mango Root Rot & Damping-Off Disease

  • Spray Carbendazim, Thiophanate-methyl, and Metalaxyl to the soil or foliage to control the fungus spread.
  • Seed & seedling treatment – Treat the seeds and seedlings with Captan or Thiram before planting to prevent disease incidence.
  • Soil fumigation – Soil fumigation involves using chemicals such as methyl bromide or chloropicrin to kill soil-borne pathogens.

Organic Control Measures of Mango Root Rot & Damping-Off Disease

  • Bio-fumigation involves growing and incorporating certain plants, such as mustard and radish, into the soil to release volatile compounds that suppress the growth of Rhizoctonia solani.
  • Composts and organic amendments such as animal manure, crop residues, and green manure can enhance soil microbial activity and suppress the growth of Rhizoctonia solani.
  • Copper-based fungicides, such as copper hydroxide, copper sulfate, and copper oxychloride, disrupt fungal cell membranes, inhibit their growth, and control the disease. These should be sprayed before the flowering and fruiting phases of the tree.
  • Plant extracts, such as extracts from neem, ginger, garlic, and turmeric leaves, are used as a foliar spray or incorporated into the soil to suppress the disease.

Preventive Measures for Control of Mango Root Rot & Damping-off Disease

  • Choose a site with good drainage and avoid planting in areas prone to flooding or waterlogging.
  • Avoid overwatering as it can lead to waterlogging and favor the growth of Rhizoctonia solani. Also, avoid overhead irrigation as it can spread the pathogen from plant to plant.
  • Planting healthy and disease-free mango seedlings is essential to prevent the spread of the disease.
  • Solarization involves covering the soil with a transparent plastic sheet to trap heat and increase soil temperature to kill fungi and other soil-borne pathogens.
  • Crop rotation is essential to reduce the buildup of soil-borne pathogens that can cause the disease.
  • Regularly monitoring the crops for signs of disease will help to find and manage the disease early before it spreads.

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Mangoes

Conclusion

The Mango Root Rot & Damping-off Disease caused by Rhizoctonia solani is a serious problem that can cause significant yield losses in mango crops. Integrated Disease Management (IDM) approach is the most effective way to manage the disease. IDM involves using a combination of cultural, biological, chemical, and preventive control measures to reduce the impact of the disease.

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Author: Reddy

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