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一、前言黄瓜霜霉病的气温达20℃左右,尤其在梅雨季节很容易发生。这种病害的发生最初是从底部叶片开始,形成淡黄色的小斑点,接着围绕叶脉迅速扩展,成为多角形病斑。夜间湿度高时就在病斑上产生许多孢子,并陆续通过气孔侵入组织,使病斑逐渐扩展。在黄瓜的塑料棚裁培中常可见到这种病的发生。黄瓜发病时长势减弱,座果及瓜条生长显著不良。这种病害要用药剂进行彻底防治是很困难的。根据加藤报导,黄瓜霜霉病容易发生在温室内光线条件好的畦段,这是由于霜霉病菌是从气孔侵入,而这些畦段的位
I. Introduction Cucumber downy mildew temperature of about 20 ℃, especially in the rainy season is very easy to happen. The onset of this disease initially begins with the bottom leaf blade forming a pale yellow spot that then rapidly expands around the veins and becomes a polygonal lesion. When the nighttime humidity is high, many spores are produced on the lesion, and one after another through the stoma to invade the tissue and gradually enlarge the lesion. In cucumber plastic shed cutting culture can often be seen in the incidence of this disease. Cucumber grows weakened at onset, fruit and melon growth significantly bad. It is very difficult to thoroughly prevent and treat this disease by using medicine. According to Kato, cucumber downy mildew is easy to occur in the greenhouse under good light conditions due to downy mildew intrusion from the stomata,