韭菜是多年生蔬菜，占地时间较长，随着连作种植年限的增加，菌源集中，疫病为害越来越严重，个别地块发病率高达７０％以上。为此，如何防治疫病的发生显得尤为重要，现将其发生及防治介绍如下。 一、发病症状 叶片受害，初为暗绿色水浸状病斑，病部缢缩，叶片变黄凋萎。天气? Leek is a perennial vegetable, covering a long time, with the continuous planting years increase, concentrated bacteria, the disease is more and more serious, the individual block incidence rate as high as 70%. To this end, how to prevent and control the epidemic is particularly important, now its occurrence and prevention are described below. First, the incidence of symptoms of leaf damage, the beginning of the dark green spot-like disease, shrinking disease, yellowing withered leaves. the weather?