茭白纹枯病过去少见,七十年代只是零星发生。八十年代以来,由于施肥水平不断提高,种植密度增加,茭白纹枯病危害逐年加重,目前已成为茭白的重要病害之一。茭白发生纹枯病后,一般减产5～10％,连作田减产20％左右。 一、症状 茭白分蘖盛期至孕茭期最易发病。发病初期,先在近水面的叶鞘上出现水渍状暗绿色的椭圆形病斑,以后逐渐扩大成云纹状。病斑中部浅灰色,外圈暗绿色,潮湿时成灰绿色。病斑由下向上蔓延,逐渐增多。茭叶和茭肉上的症状与叶鞘上的病斑相似。发病严重时,茭叶提早枯死,茭肉干瘪,失去食用价值。高温多雨或田间湿度大时,病部表面集结白色菌丝团,逐渐生成黑褐色的菌核。但叶鞘上的菌核,大都附着于叶鞘内侧。菌核成熟后易掉落于土表,成为第二年的初侵染来源。 Whitehead blight is rare in the past, sporadically in the 1970s. Since the 1980s, due to the continuous improvement of fertilization level and the increase of planting density, the harm of white blotch blight has been increasing year by year, and now it has become one of the important diseases of catapult. Epiphytic whitehead blight, the general reduction of 5 to 10%, even the crop reduction of about 20%. First, the symptoms 茭 white tiller peak period of pregnancy is most vulnerable to disease. Early onset, first in the water near the surface of the leaf sheath appeared water-like oval green stains lesions, and later gradually expanded into a cloud-like. Middle lesion light gray, dark green outer ring, when damp gray. Lesions spread from the bottom up, gradually increased. Symptoms on the leaves and pterygium are similar to those on the leaf sheath. When the disease is serious, the early leaves of dead leaves, scanty shriveled, loss of food value. When the temperature is high and rainy or the field humidity is high, the white mycelium collects on the surface of the diseased part and gradually forms the dark brown sclerotia. However, sclerotia on the sclerotia, mostly attached to the leaf sheath inside. Sclerotia easily fall into the soil surface after maturity, becoming the source of the second year of early infection.