一、症状识别常在叶、叶柄、茎上发病。叶片多从叶尖或叶缘发病,产生褐色小病斑,有黄色晕圈,扩大后呈不规则形。潮湿时,病斑上密生黑霉(分生孢子)。茎、花梗发病,产生长圆形黑褐色稍凹陷病斑,易折断,种子不饱满,并带有病菌。二、发生原因由胡萝卜链格孢引起。病菌在种子和病残体上越冬。种子带菌率高,引起苗立枯。第二年新病斑上长出的 First, the symptoms often identify leaves, petioles, stem disease. More leaves from the leaf tip or leaf margin disease, resulting in small brown spots, yellow halo, expand the irregular shape. Moisture, the lesion on the black mold (conidia). Stems, peduncles disease, resulting in oblong dark brown slightly depressed lesion, easy to break, the seeds are not full, and with bacteria. Second, the cause is caused by Alternaria alternata. Germs overwinter on seeds and diseased bodies. Seed carrying rate is high, causing seedlings withered. The second year the new disease spots grow