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病害的流行要具备三个因素:一是病原菌大量存在;二是种植的是感病品种;三是环境条件适合病害发生。黄瓜霜霉病的流行与温湿度有着密切的关系,特别是湿度。根据试验,孢子囊在5～30℃均可萌发,适温在15～20℃,侵入寄主的温度10～25℃,最适的温度是16～24℃,若低于15℃或高于28℃,不利于霜霉病的发生发展。高湿是发病的重要条件,湿度愈大孢子囊形成愈快,数量也愈多。如果相对湿度在83％以上,4小时就可产生孢子囊,若相对湿度低于60％时,就不产生孢子囊。另外,霜霉菌的萌发和侵入,要
Prevalence of diseases to have three factors: First, the presence of large numbers of pathogens; second is the susceptible varieties planted; third is the environmental conditions suitable for disease. Cucumber downy mildew prevalence and temperature and humidity are closely related, especially humidity. According to the test, the sporangia germinate at 5 ~ 30 ℃, the suitable temperature is 15 ~ 20 ℃, the host invading temperature is 10 ~ 25 ℃, the optimum temperature is 16 ~ 24 ℃, if below 15 ℃ or above 28 ℃, is not conducive to the occurrence and development of downy mildew. High humidity is an important condition for onset, the more the humidity, the faster the formation of sporangia, the greater the number. If the relative humidity of 83% or more, 4 hours can produce sporangia, if the relative humidity is less than 60%, no sporangia. In addition, downy mildew germination and invasion, to