Leaf spot menace in sugarcane

THE LEAF spot disease Drechslera sacchari is also known as eye spot. The incidence is noticed in some of the popular cultivars like Co Si 95071, Co Si 86071, Co86010 and Co G 93076.

The initial symptom of the disease appear as small water soaked spots which are darker than the surrounding areas. These spots become more elongated. The central portion of spot is reddish brown in colour and later becomes grey coloured, surrounded by yellow patches. Reddish brown streaks on runners develop from these spots, extending from the lesion towards the leaf tip along the veins. The leaf spots and runners coalesce together to form large patches of reddish brown tissues and drying of leaves is noticed in severe infections. The production of `streaks' or `runners' is attributed to the secretion of toxin `helminthosporoside' by the fungus.

The disease spreads through moisture on cane leaves due to rain drops or dew drops. Young plants are more susceptible than mature ones. The incidence is more on the ratoon crop due to the build up of inoculum. Cloudiness, high humidity with drizzle and low night temperature favours the disease. The following control measures are suggested for the management of the disease.

- Removing and burning of the severely infected lower leaves to destroy the inoculum of the pathogen.

- Spraying of Carbendazim - 200 gm per acre or Mancozeb - 400 gm per acre twice at 15 days interval.

- The fungicides are to be dissolved in 200 litres of water per acre and any one of wetting agents like Sandovit, Triton and Teepol is to be added at the rate of 5 ml per 10 litres of liquid spray.

S. Muthusamy, S. Geetha & W. Wilfred Manuel Sugarcane Research Station Tamil Nadu Agricultural University Sirugamani-639 115

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