Đang chuẩn bị liên kết để tải về tài liệu:
THE DISEASES OF PLANTS

Plants have diseases just as animals do; not the same diseases, to be sure, but just as serious for the plant. Some of them are so dangerous that they kill the plant; others partly or wholly destroy its usefulness or its beauty. Some diseases are found oftenest on very young plants, others prey on the middle-aged tree, while still others attack merely the fruit. Whenever a farmer or fruit-grower has disease on his plants, he is sure to lose much profit. You have all seen rotten fruit. This is diseased fruit. Fruit rot is a plant disease. It costs. | THE DISEASES OF PLANTS THE CAUSE AND NATURE OF PLANT DISEASE Plants have diseases just as animals do not the same diseases to be sure but just as serious for the plant. Some of them are so dangerous that they kill the plant others partly or wholly destroy its usefulness or its beauty. Some diseases are found oftenest on very young plants others prey on the middle-aged tree while still others attack merely the fruit. Whenever a farmer or fruit-grower has disease on his plants he is sure to lose much profit. You have all seen rotten fruit. This is diseased fruit. Fruit rot is a plant disease. It costs farmers millions of dollars annually. A fruit-grower recently lost sixty carloads of peaches in a single year through rot which could have been largely prevented if he had known how. Many of the yellowish or discolored spots on leaves are the result of disease as is also the smut of wheat corn and oats the blight of the pear and the wilt of cotton. Many of these diseases are contagious or as we often hear said of measles catching. This is true among others of the apple and peach rots. A healthy apple can catch this disease from a sick apple. You often see evidence of this in the apple bin. So too many of the diseases found in the field or garden are contagious. Pg 123 Sometimes when the skin of a rotten apple has been broken you will find in the broken place a blue mold. It was this that caused the apple to decay. This mold is a living plant very small certainly but nevertheless a plant. Let us learn a little about molds in order that we may better understand our apple and potato rots as well as other plant diseases. If you cut a lemon and let it stand for a day or two there will probably appear a blue mold like that you have seen on the surface of canned fruit. Bread also sometimes has this blue mold at other times bread has a black mold and yet again a pink or a yellow mold. These and all other molds are tiny living plants. Instead of seeds they produce many very .