Red Rot of Sugarcane
Causal Organism:
- Name: Colletotrichum falcatum
- Classification:
Symptoms:
- Initial Symptoms:
- Red lesions on the leaf midribs.
- Wilting and yellowing of leaves, especially the older ones.
- Advanced Symptoms:
- Red discoloration of the internodes in the sugarcane stem.
- Presence of white patches across the red discoloration, giving a red-and-white streaked appearance.
- Spongy, water-soaked, and rotten internodes emitting a sour smell.
- Necrotic streaks extending through the nodes and internodes.
- Longitudinal splitting of canes, leading to a hollow stem.
Etiology:
- Pathogen Characteristics:
- Colletotrichum falcatum produces conidia that are spindle-shaped, hyaline (colorless), and single-celled.
- The fungus thrives in warm and humid conditions, which are typical in sugarcane-growing regions.
- The pathogen can survive in infected cane debris and soil.
Disease Cycle:
1. Primary Inoculum:
- Overwinters in infected plant debris and soil.
- Conidia are produced from the primary inoculum.
2. Dissemination:
- Spread by wind, rain splashes, irrigation water, and mechanical means (tools, animals, humans).
3. Infection:
- Conidia land on the sugarcane plant and germinate under favorable conditions (high humidity, temperature around 25-30°C).
- The fungus penetrates the plant through wounds or natural openings like stomata.
4. Colonization:
- Once inside the plant, the fungus produces mycelium, which spreads through the vascular system, leading to blockage and symptom development.
5. Secondary Spread:
- Occurs via conidia produced on infected plants, continuing the disease cycle.
Management:
Managing red rot of sugarcane requires an integrated approach involving the use of healthy planting material, crop rotation, resistant varieties, physical removal of infected plants, and appropriate chemical treatments. Regular monitoring and early detection are critical to effectively control the spread of this devastating disease.
1. Cultural Methods:
- Selection of Healthy Setts: The best way to control red rot is to select setts for planting from healthy plants in a disease-free area.
- Crop Rotation: Rotate the red rot affected field with rice for one season and other crops for two seasons.
- Resistant Varieties: Grow recommended resistant and moderately resistant varieties such as Co 86032, Co 86249, CoSi 95071, CoG 93076, CoC 22, CoSi 6, and CoG 5.
2. Physical Methods:
- Removal of Affected Clumps: Remove the affected clumps at an early stage and perform soil drenching with Carbendazim 50 WP (1 gm in 1 liter of water).
- Set Treatment: Dip the cut ends and entire setts in a fungicide solution, such as one percent Bordeaux mixture.
- Destruction of Infected Material: If the disease is noticed in the field, collect and destroy the infected leaves and canes by burning.
3. Chemical Methods:
- Sett Treatment: Adopt sett treatment with Carbendazim before planting (Carbendazim 50 WP, 0.5 gm in 1 liter of water, or Carbendazim 25 DS, 1 gm in 1 liter of water) along with 2.5 kg of urea in 250 liters of water.
- Fungitoxic Chemicals: Use fungitoxic chemicals like Bavistan, Benomyl, Topsin, and Aretan at 0.1 percent for 18 minutes at 52ºC for dipping setts to achieve almost complete elimination of rot infection.
Smut of Sugarcane
Causal Organism:
- Name: Sporisorium scitamineum (formerly known as Ustilago scitaminea)
- Classification:
- Kingdom: Fungi
- Phylum: Basidiomycota
- Class: Ustilaginomycetes
- Order: Ustilaginales
- Family: Ustilaginaceae
- Genus: Sporisorium
- Species: scitamineum
Symptoms:
1. Whip-like Structure: The most distinctive symptom is the formation of a black, whip-like structure called a "smut whip" or "smut sori" emerging from the spindle leaves or the growing points of the cane. This whip can reach up to 50 cm in length.
2. Stunted Growth: Affected plants exhibit stunted growth due to the disruption of the apical meristem.
3. Thin Stalks: The cane stalks become thin and often have reduced internodal lengths.
4. Leaf Symptoms: Leaves may become narrow, curled, and show chlorosis (yellowing).
5. Galls: In some cases, galls or swellings may appear on the nodes of the cane.
6. Reduced Yield: Infected plants show a significant reduction in sugar content and overall yield.
Etiology:
- Pathogen: Sporisorium scitamineum produces teliospores, which are thick-walled resting spores. These spores are the primary means of survival and spread of the fungus.
- Dispersal: The teliospores are dispersed by wind, rain, irrigation water, and contaminated tools and equipment. They can also spread through infected seed pieces used for planting.
- Germination: The teliospores germinate in the presence of moisture and produce basidiospores, which then infect the young shoots of sugarcane.
Disease Cycle:
1. Survival: The teliospores survive in the soil, on plant debris, or in infected seed cane.
2. Germination and Infection: Under favorable conditions, teliospores germinate and produce basidiospores, which infect the meristematic tissues of young sugarcane shoots.
3. Colonization: The fungus colonizes the internal tissues of the host plant, especially the growing points.
4. Smut Whip Formation: As the fungus grows, it induces the formation of the smut whip, which contains masses of teliospores.
5. Dispersal: The smut whip ruptures, releasing teliospores into the environment, thus completing the cycle.
Management:
Cultural Method:
1. Resistant Varieties: Grow resistant and moderately resistant varieties such as Co 86249, CoG 93076, CoC 22, CoSi 6, and CoG 5.
2. Ratooning Management: Discourage ratooning of diseased crops having more than 10% infection.
3. Companion Cropping: Grow Cajanus cajan (pigeon pea) as a companion crop between rows of sugarcane to substantially reduce the secondary spread of the disease.
Physical Method:
1. Seed Treatment: Treat seed setts with Aerated Steam Therapy (AST) at 50°C for 1 hour or in hot water at 50°C for 30 minutes, or at 52°C for 18 minutes.
2. Roguing: Remove smut whips using gunny bags or polythene bags, dip them in boiling water for 1 hour, and uproot and burn diseased clumps.
Chemical Method:
1. Fungicide Treatment: Treat setts with fungicides such as Triadimefon (1 gm in 1 liter of water) or Carbendazim (1 gm in 1 liter of water) for 10 minutes.
2. Spot Treatment: Spray infected stools with a small amount of a 10% solution of Roundup using a small handheld sprayer.
3. Severe Infestation: In severe cases, spray the entire block with glyphosate (360 g/L) at 5-7 liters per hectare.
Wilt of sugarcane
Causal Organism
- Causal Organism: Fusarium sacchari
- Classification:
- Kingdom: Fungi
- Phylum: Ascomycota
- Class: Sordariomycetes
- Order: Hypocreales
- Family: Nectriaceae
- Genus: *Fusarium*
- Species: *F. sacchari*
Symptoms
- Initial Symptoms: The disease often begins with the yellowing and wilting of the lower leaves, which gradually spread upward.
- Leaf Symptoms: Infected leaves display a pale green or yellowish coloration, with the midrib and veins turning red or brown.
- Stem Symptoms: In the stem, the disease manifests as red or brown streaks, and the vascular bundles often turn brown, a sign of the systemic spread of the fungus.
- Other Symptoms: Plants may exhibit stunted growth, reduced tillering, and in severe cases, complete wilting and death. Internally, the pith tissue may become reddish-brown and desiccated.
Etiology
- Pathogen Characteristics: Fusarium sacchari produces both macroconidia and microconidia. The macroconidia are sickle-shaped and multi-septate, while microconidia are smaller and typically single-celled.
- Survival and Spread: The fungus survives in soil and plant debris and can spread through infected planting material, water, soil movement, and tools.
Disease Cycle
1. Primary Infection: The fungus infects sugarcane through wounds or natural openings in roots and lower stems.
2. Colonization: After entry, F. sacchari colonizes the vascular system, obstructing water and nutrient transport.
3. Symptom Development: As the fungus spreads, it disrupts plant physiology, leading to wilting and other symptoms.
4. Secondary Spread: The pathogen produces conidia that can be spread by wind, water, and agricultural practices, leading to new infections.
5. Survival: F. sacchari can persist in soil and plant debris for extended periods, waiting for suitable conditions to infect new plants.
Management
1. Cultural Method:
- Selection of Healthy Seed Setts: Use seed setts from disease-free areas for planting.
- Resistant Varieties: Grow resistant varieties like Co 617 and B.P.17, which are more resistant than other varieties.
- Crop Rotation: Rotate with non-host crops to reduce soil inoculum levels.
- Root Borer Management: Control root borer populations to prevent secondary infections.
- Water Management: Avoid prolonged drought and waterlogging to reduce plant stress and susceptibility.
- Hygienic Practices: Maintain field sanitation by removing and destroying infected plant debris.
2. Chemical Method:
- Minor Element Treatment: Dip the setts in 40 ppm of boron or manganese, or spray the plants with either of these minor elements to reduce disease intensity.
- Fungicide Treatment: Treat seed setts with Bavistin (carbendazim) at 0.1% before planting.
- Root Zone Application: Apply carbendazim at 2 g/liter of water in the root zone area and repeat the application at 15-day intervals.
Pokkah Boeng of Sugarcane
Causal Organism
- Causal Organism: Pokkah boeng of sugarcane is caused by fungi from the genus *Fusarium*, specifically *Fusarium moniliforme* (now classified as *Fusarium verticillioides*).
- Classification:
- Kingdom: Fungi
- Phylum: Ascomycota
- Class: Sordariomycetes
- Order: Hypocreales
- Family: Nectriaceae
- Genus: Fusarium
- Species: *Fusarium verticillioides*
Symptoms
- Early Symptoms: Initial symptoms include chlorosis (yellowing) of the young leaves. These yellowed leaves may have a distorted and wrinkled appearance.
- Advanced Symptoms:
- The leaves develop necrotic streaks, which are brown to reddish-brown and often run parallel to the veins.
- Leaf tips may become twisted or curled, leading to a characteristic "pokkah boeng" (distorted top) appearance.
- In severe cases, the growing point of the cane (apical meristem) can be destroyed, resulting in a cessation of cane elongation and death of the shoot.
- Internodes may become shortened and malformed.
- Other Symptoms: The stem may show red or brown internal discoloration, and secondary bacterial infections can cause rotting of the tissues.
Etiology
- *Fusarium verticillioides* is a soil-borne pathogen that can survive in crop residues and soil.
- The fungus produces spores (macroconidia, microconidia, and chlamydospores) that spread through water, wind, contaminated tools, and infected planting material.
- Warm and humid conditions favor the growth and spread of the pathogen.
Disease Cycle
- Primary Inoculum: The disease cycle begins with the survival of the fungus in crop residues, soil, and infected planting material.
- Dissemination: The spores are disseminated by wind, rain splash, irrigation water, and mechanical means (e.g., contaminated tools and equipment).
- Infection: Spores infect the young and rapidly growing tissues of sugarcane, especially through wounds or natural openings. The fungus grows intercellularly and intracellularly, leading to the development of symptoms.
- Secondary Spread: The pathogen continues to produce spores on infected plants, which can infect nearby healthy plants, perpetuating the disease cycle.
Management
- Cultural Practices:
- Use disease-free planting material to prevent initial infection.
- Implement crop rotation with non-host crops to reduce soil inoculum levels.
- Destroy crop residues by deep plowing or burning to eliminate sources of the pathogen.
- Ensure good drainage in fields to reduce waterlogging, which favors fungal growth.
- Chemical Control: Fungicides, such as benomyl or carbendazim, can be applied as a preventive measure, especially in nurseries and young crops.
- Biological Control: Employ antagonistic fungi such as *Trichoderma spp.*, which can inhibit the growth of *Fusarium* through competition and mycoparasitism.
- Resistant Varieties: Planting resistant or tolerant varieties of sugarcane can significantly reduce the impact of the disease. Breeding programs aim to develop and promote such varieties.
- Monitoring and Early Detection: Regular field scouting to identify early symptoms and take timely action can help manage the spread of the disease.
Grassy shoot disease (GSD) of sugarcane
Causal Organism
Grassy shoot disease (GSD) of sugarcane is caused by a phytoplasma, specifically a type of bacterium-like organism that lacks a cell wall and is obligate to the plant and insect hosts for survival. Phytoplasmas belong to the class Mollicutes.
Symptoms
General Symptoms:
Excessive Tillering: The most characteristic symptom is the production of numerous thin, grassy shoots due to excessive tillering.
Yellowing: Young leaves exhibit yellowing (chlorosis), particularly at the leaf tips.
Stunted Growth: Infected plants often show stunted growth.
No Cane Formation: There is a significant reduction in cane formation, with affected plants producing very little or no cane.
Leaf Symptoms:
Small and Narrow Leaves: The leaves of infected shoots are smaller, narrower, and pale green to yellow.
Rosetting: Leaf rosettes may form at the top of the shoots.
Root Symptoms:
Poor Root Development: The root system of affected plants is typically poorly developed.
Etiology
Phytoplasma Characteristics:
Phytoplasmas are small (200-800 nm in diameter), pleomorphic, and lack a cell wall.
They are restricted to the phloem tissue of plants and are transmitted by phloem-feeding insect vectors.
Transmission:
The primary vector of GSD phytoplasma is the leafhopper (Pyrilla perpusilla).
Transmission occurs when the leafhopper feeds on an infected plant and then moves to a healthy plant, transmitting the phytoplasma through its saliva.
Disease Cycle
Primary Source of Inoculum:
The disease perpetuates through infected plant material (setts) used for propagation.
Infected perennial grasses and weeds can also serve as reservoirs of the phytoplasma.
Vector Transmission:
Leafhoppers acquire the phytoplasma while feeding on the phloem sap of infected plants.
The phytoplasma multiplies within the leafhopper and is transmitted to healthy plants during subsequent feeding activities.
Plant-to-Plant Spread:
Within the plant, the phytoplasma spreads systemically through the phloem.
Infected plants exhibit symptoms that develop as the phytoplasma moves to new growth areas.
Management
Cultural Practices:
Use of Disease-Free Planting Material: Ensure the use of healthy, phytoplasma-free seed cane (setts).
Rogueing: Regularly inspect fields and remove and destroy infected plants to reduce the inoculum source.
Vector Control:
Insecticide Applications: Use appropriate insecticides to control the leafhopper population, thus limiting the spread of the phytoplasma.
Biological Control: Encourage the presence of natural predators of leafhoppers.
Resistant Varieties:
Development and planting of sugarcane varieties that show resistance to the phytoplasma or the leafhopper vector.
Field Hygiene:
Maintain field hygiene by removing weeds and alternate hosts that can harbor the phytoplasma.
Ensure proper sanitation of tools and equipment to prevent mechanical transmission.
Crop Rotation:
Implement crop rotation with non-host crops to break the disease cycle and reduce the phytoplasma inoculum in the soil.
Heat Therapy:
Treating seed cane with hot water (at 50°C for about 30 minutes) can help eliminate the phytoplasma from planting material.
Monitoring and Surveillance:
Regular monitoring and early detection through field surveys and diagnostic testing to manage the disease effectively.
Source
https://agritech.tnau.ac.in/crop_protection/crop_prot_crop%20diseases_cash%20crops_sugarcane.html