Spores are produced and released during the night and spread throughout the rice field. The fungus overwinters in diseased rice seed and straw and in alternate weed hosts. Optimum conditions for disease development are average daily temperatures between 73 and 79 degrees F, and prolonged leaf wetness and high relative humidity. High soil residues of available nitrogen increase disease. The addition of sodium silicate reduces disease.
Susceptible varieties have more severe blast when they are grown in sandier soils.
Most varieties grown in Mississippi have a moderate level of resistance to blast. The Extension Service publishes a list of the disease reaction of the varieties grown in Mississippi. The use of varieties with resistance to blast is a necessity. Varieties with a high degree of resistance should be planted on sandier soils. The flood should be maintained throughout the growing season.