水稻紫鞘病是我国南方稻区生产上的一个新问题,发生面广,为害较重。经1978~1984年的研究,找到了引起紫鞘的病原茵是Acrocylindrium oryzae。带菌种子是本病的主要初次侵染来源;保存在干燥状态下的病稻草也有传病作用,稻田后期的某些虫、螨,可以传播病菌。紫鞘病病原菌的主要侵染方式是系统侵染。水稻孕穗期喷雾接菌,也能形成紫鞘,但注射法伤口接种时,大多形成虎纹斑烂鞘。因此,紫鞘是水稻叶鞘腐败病的又一种典型症状。病菌生长与产生孢子的适温为25~30℃。孕穗期接菌,其潜育期:30℃为1天,25~28℃为2天,23℃为3天,19℃为4天。

The purple-sheath disease of rice is prevalent in many rice growing reg-ionsin South China.The causal organism of the disease is identified as Aco-rcylindriumoryzae Sawada.The primary sourse of the dieasse is found to be seedborne.During germination of the seeds,the pathogen will invade the young shoots,and the growing point of the seedling,then the rudimentary he-ads and the sheath of flag leaf are infected,The pathogen in the disease rice straws keeping in dry condition is also the source of infection.Some insects,such as planthoppers,aphids and mites are found carring the pathogen,and they will probably transmit the disease in the field.
The symptoms of the disease depends upon the period of infection.If the infection takes place at the booting stage by inject inoculation,it will induces the sheath rot and it inducey purple-sheath by spraing inoculation.That is to say,urple-sheath is one typical symptoms of sheath rot of rice.
The optimum temperature for the growth and the spororation of the pathogen is found to be 25-30℃.During the booting stage the symptoms of the leaf sheath of the flag leaf often appear af 30℃ 24 hours after inoculation,at 25-28℃,two days,at 23℃ three days,and at 19℃ four days respectively.