The fungus can over winter in diseased crop residue or in seed. Seed is considered an important primary source for the fungus especially in temperate areas where only one rice crop is grown per year. Straw management practices are also believed to be an important factor in pathogen carry over from season to season. Greenhouse studies have shown that many grasses serve as hosts for the pathogen, but it is not completely clear what role weeds may play in nature. Leaf wetness from dew or other sources is needed for the fungus to infect rice.
Temperature also impacts infection.
Warmer temperatures also speed the development of lesions on rice. Warm nighttime temperatures coupled with high humidity favor spore formation. Spores can be produced on an ongoing basis and are dispersed by the prevailing winds. Warm night time temperatures, high humidity and long dew periods enhance disease development. This year's warm, humid weather appeared to favor the disease.