Red rot is a devastating disease that affects sugarcane crops globally and is caused by the fungus Colletotrichum falcatum. The Disease was discovered in India in the early twentieth century and rapidly spread to other sugarcane-growing regions. Red rot is a significant threat to sugarcane production because it lowers sucrose content, causes yield loss, and results in significant economic losses for farmers. The fungus enters the plant through wounds or natural openings and colonizes the stalk’s interior tissues, causing rotting and discoloration.
Controlling red rot requires proper management practices such as planting resistant varieties, removing infected plant debris, and administering fungicides. Crop rotation and keeping healthy soil conditions can also help prevent disease spread.
Red Rot Management in Sugarcane
The Causal Organisms of Red Rot and Identification of Pathogen
The fungus Glomerella tucumanensis, also known as Colletotrichum falcatum, is responsible for red rot disease in sugarcane. The pathogen typically appears dark brown to black, with globose structures between 65 and 250 m in diameter on leaf sheaths and blades. These entities frequently exist alone or in groups, creating small pathways between the vascular bundles. The resting structures, or sclerotia, have walls up to eight cells thick, are pseudo-parenchymatous on the inside, and have a faintly papillate ostiole.
The Disease Cycle of Red Rot Disease
Red-rot disease cycle Colletotrichum falcatum’s fungus spores cause red rot sugarcane disease. Wounds, natural openings, or soil-infected plant waste allow the spores to enter the plant. The fungus develops conidia, asexual spores spread by wind, rain, and irrigation. Conidia can infect other sugarcane plants or make sclerotia on soil surfaces.
During the rainy season, the Disease spreads so rapidly that the entire crop dies, and no infected cane is harvested. Sclerotia can wait in the soil for optimal conditions to infect the next crop. When conditions are right, sclerotia germinate and create new fungal spores, restarting the disease cycle.
Causes/Conditions Favorable for Red Rot Disease in the Field
- Spores from infected crop debris washed into the soil can infect newly planted seeds or seedlings, even though the fungus can only live in the soil for a short period.
- Disease spores are dispersed from infected plants via breeze, rain, heavy dew, and irrigation water. The spores are produced in the midrib or stalks.
- The Disease thrives in cool, damp conditions, consistently damp soils, and monocultures.
- There may be an uptick in illness rates due to drought.
- The fungus can also infect corn and sorghum, considered intermediate hosts.
Symptoms of Red Rot Disease
- Symptoms of red rot disease in sugarcane include changing the color of the leaves from green to yellow and drying that begins at the bottom of the plant and moves upwards.
- If the fungus spores get past the leaf sheath, reddish spots may develop on the underside of the leaf’s midrib.
- After the infection, the external signs appear 16–21 days later, and the cane usually dries out in another ten days.
- The inner region of the affected cane exhibits a reddish color with sporadic white tinges when it is divided, and the pith may contain a blackish-brown liquid with an alc