DISEASE: RedRot
PATHOGEN: Colletotrichum falcatum (Glomerella tucumanensis)
HOSTS: Sugarcane
Symptoms and Signs
Red rot is usually considered as a stalk and a seed-piece disease.
Leaf Symptoms
•Tiny reddish lesions on the upper surface of the lamina.
•Minute red spots on the upper surface of the midrib in both the directions.
•Later on becomes straw colored in the center with the development of black acervulli and dark reddish brown margins.
Stalk Symptoms
Drying up of the 3rd & 4th leaf of the crown at margins. Later, the entire crown dries up & drops down.
Brown or reddish brown stripes appear externally at nodal region.
On splitting, the internal tissue becomes red with white transverse bands.
Tissues emit alcoholic sour smell.
Tiny acervuli develop on outer surface of shrinkled upper internodes.
Cottony gray fungal mass develops in the pith region of the internodes and sporulates abundantly.
In the later stages of the disease, red rot may cause standing cane to “break down“. Sugarcane lodging caused by Red Rot.
Pre disposing (environmental) factors
Warm ‐ humid weather conditions with intermittent rains.
Mono-culturing of sugarcane,
Successive ratoon cropping,
Water logged conditions
Injuries by sugarcane borers and sugarcane weevils.
Disease cycle
The fungus is sett-borne. The fungus also persists in the soil on the diseased clumps and stubbles as acervuli. The primary infection is mainly from infected setts.
Secondary spread in the field may be through irrigation water and cultivation tools. The rain splash, air currents and dew drops also help in the spread of conidia from the diseased to healthy plants in the field. The fungus also survives on collateral hosts like Sorghum vulgare, S. halepense and Saccharum spontaneum.
Management strategy
Grow resistant varieties like CO 6907, CO 7219, CO 8013, CO 8021, CO 7706, CO A 7602, CO A 89082, CO A 89085, 87 A 397, CO T 8201, etc.
Removal and destruction of infected plant debris, stubbles and trash.
Deep tillage .
Crop rotation.
Use disease free setts.
Avoid ratooning of the diseased crop.
Avoid flood irrigation.
Soak the setts in 0.1% Carbendazim solution for 20 minutes before planting.
Hot Water/ Steam treatment
Soak setts in hot water at 52˚C for 30 min followed by steeping in 0.1% carbendazim solution.
OR
Setts can be treated with aerated steam (AST) at 52˚C for 4 to 5 hours.