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职称英语卫生类考试考前每日一练 Diseases of Agricultural Plants Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plants: forty are known to attack corn, and about as many attack wheat. The results of unchecked plant disease are all too obvious in countries which have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries which are now amply fed by their agricultural products, there could soon be critical food shortages. It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavalsdisastrous to the order of the world. Some plants have relative immunity to a great many diseases, while others have a sus-ceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blightmay be but a local infection easily controlled, on the other hand it can attack particular plants in a whole region or nation. An example is the blight which killed virtually every chestnut tree in North American. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments. | 
