【摘要】 <正> 番茄晚疫病(Phytophthora infestans)是世界性的病害,在很多国家和地区广为流行。我国种植番茄的地区也常遭此病危害,特别是南方的一些省市。北京地区的番茄历史上很少受到晚疫病威胁,而七十年代以来有两次大流行,造成严重减产。为此,我们对近年晚疫病会在北京地区上升成为主要病害的原因和规律进行了调查研究,所得结果如下。更多还原

【Abstract】 From investigations conducted over many years in Beijing, it has been proved that the increasing severity of tomato late blight in recent years is related to the change in planting system of tomato, i. (?). the rising practice of using greenhouses in winter and plastic canopies in spring. Tomato late blight occurs more and more often in greenhouses and plastic canopies, where the pathogen can accomplish its annual infection chains easily. The fungus in plastic canopies is the main source of infection for tomato late blight in fields. Late blight lesions are often found on tomato plants growing in fields nearby a tainted plastic canopy in as early as April or May. But the epidemic of late blight in fields is predominantly determined by weather conditions of May,June and July, and the relative humidity is a key factor. Over 75% average relative humidity per tendays may be used as a criterion for forecasting blight. As soon as such a period of high humidity appears, chemical treatment is recommended. Generally, epidemic only breaks out when humid conditions of>75% go on for twenty to thirty days. If more than ten days of drought and high temperature intervenes in this period, or no ten-day high humidity appears at all, the spread of the disease will slow down or not happen. A control scheme for the tomato late blight in Beijing is suggested.更多还原