棉花凋枯病又名红叶茎枯病。据我们多年观察,在苗期就开始发生,雨后天晴,棉苗叶片上出现失绿的黄白斑点,是凋枯病的最初症状。不过那时棉株正处于营养生长的旺盛阶段,这种斑点会暂时消失。7月中下旬,棉花进入盛花期,我区常处于伏旱高温季节,在水肥条件尤其钾肥不能满足需要的情况下,棉株营养生长和生殖生长矛盾加剧,造成凋枯病的迅速蔓延。其主要症状是:自上部功能叶,即主茎顶部往下第三、四片叶和果枝上部长成形的新生叶,叶尖沿主脉两侧及叶的边缘开始失绿,呈现黄白斑点,随后变为黄褐色或红褐色 Cotton blight, also known as red stem blight. According to our many years of observation, seedling began to occur, after the rain sunny, cotton leaves appear green and yellowish green spots, is the first symptom of blight. However, at that time, the cotton plant was in the vigorous stage of vegetative growth, and the spots would disappear temporarily. In mid and late July, the cotton entered the full flowering period, and my area is often in the period of drought and high temperature. Under the conditions of water and fertilizer, especially the potash fertilizer can not meet the needs, the contradiction between vegetative and reproductive growth of cotton plants aggravates, causing the rapid spread of the blight. The main symptoms are: from the upper part of the function leaves, that is, down from the top of the main stem of the third and fourth leaves and fruit branches on the length of the new shaped leaves, leaf tips along the main vein on both sides and the edge of the leaves began to green, showing yellow spots , Then turned brown or reddish brown