秧苗素质、外界环境及病菌三者对水稻立枯病的发生有着相互的影响。在外界环境中,低温是立枯病发生的主导因素。水稻幼苗生长的最适温度为20～25℃,最低温度为13℃。稻苗在持续低温的情况下,生长矮小,根数稀少,而在30℃高温情况下易引起秧苗徒长,生长柔弱,抗病力减弱,极易被立枯病菌侵染。立枯病菌种类很多,有的立枯病菌在3℃以上就 Seedling quality, external environment and pathogens have the mutual influence on the occurrence of rice blight. In the external environment, low temperature is the dominant factor in the occurrence of blight. The optimum temperature for rice seedling growth is 20 ~ 25 ℃ and the minimum temperature is 13 ℃. Under the condition of continuous low temperature, the rice seedlings grow little and their numbers are few. Under the condition of high temperature of 30 ℃, they are easy to cause the growth of seedlings, weak growth, weakened disease resistance and easily infested by Rhizoctonia solani. Rhizoctonia many species, and some Rhizoctonia in more than 3 ℃