Symptoms appear on leaves and ripening grains. Small dark lesions occur on the roots or the early leaves. Parts of the seedlings above lesions are blighted and may die. Circular to oval spots (3-10mm in diameter) with dark brown margins appear on the leaves. These larger spots show many light brown or white spots in the center. The kernels may shrivel and become brittle. Infected grain is usually dark colored, chalky, brittle and shriveled and reduced in viability. On the glumes reddish brown spots appear. The kernells may shrivel and become brittle.
The disease is caused by the seed-borne fungus of T. Padwickii, an asexually-reproducing fungus that infects seeds of rice. It is responsible for seed discoloration, seed rot and seedling blight. It's occurrence has been recorded primarily in tropical regions. Humidity and high temperatures are conducive to the growth of the fungi. The fungi can survive as sclerotia in plant debris and soil.
Treat seeds with Thiram, Captan or Mancozeb at 2g/kg. Treat seeds with hot water at 54°C for 15 minutes for best results for germination and disinfection. Burn the stubbles and straw in the field. Apply a formulation of rice rhizosphere inhabiting bacteria called pseudomonas flourescens, in powdered talc at the rates of 5 and 10 per Kg.
Always consider an integrated approach with preventive measures together with biological treatments if available. Use fungicide sprays of Chlorothalonil, Mancozeb, Carboxin, Polyoxin and Iprobenfos to control grain discoloration.