Symptoms
Red rot is a fungal disease of the stalk which is often associated with stress and over-maturity. Both drought and flooding may lead to red rot development.

In standing crops, symptoms include death of the shoot and in pale coloured stalks. a reddish to purple colour of the rind. Under favourable conditions, the disease can quickly lead to crop death and rapid stalk deterioration. To recover any commercial sugar (without condemnation of the cane at the mill), such crops should be harvested immediately.

The longitudinal slicing of diseased stalks reveals a reddening of internal tissues. Characteristically, the reddening is interrupted by white patches elongated at right angles to the long axis of the stalk. There are a number of causal agents which lead to stalk reddening but only red rot gives rise to these light coloured patches.

Varieties range in resistance to this disease. In susceptible varieties, the disease may rapidly progress through the length and width of the stalk.

The fungus also may invade other sugarcane tissues. Red rot lesions in the leaf midrib are commonly associated with planthopper egg punctures. On rare occasions, the disease may invade sugarcane planting material and contribute to poor germination.

Cause
The causal agent of red rot is the fungus Glomerella tucumanensis. Transmission is by air-borne spores which infect growth cracks in the stalk, leaf scars, or surface wounds.

Distribution
The disease may occur throughout Queensland but is more severe in drought conditions. Drought-stressed, over-mature crops tend to be the most susceptible, though the disease has occurred in northern Queensland when crops have been flooded. The variety Dart in the Broadwater mill area suffered losses due to severe red rot infection.

Assessment of Severity
Timing and inspections
Red rot is normally only recorded in crops where significant stalk death has occurred. Inspections therefore should be immediately before or during the crushing season. The disease is more likely to be seen as the season progresses.

Assessing severity
The disease is recorded as area suffering significant crop loss. There is no severity scale.

History of Incidence
In recent times, little red rot has been reported due mainly to the resistance of the current commercial varieties.