THE DISEASES OF PLANTS 103 



decayed fruit in the bin or on the trees is destroyed in 

 the same manner. Never throw such decayed fruit into 

 the garden or orchard, as it may cause disease the follow- 

 ing year. 



Second, you can often kill spores on seeds before they are 

 planted, and thus prevent the development of the fungus. 

 (See pages 107-109). 



Third, often the foliage of the plant can be sprayed with 

 a poison that will prevent the germination of the spores 

 (see pages u i-i 15). 



Fourth, some varieties of plants resist disease much 

 more stoutly than others. We may often select the 

 resistant form to great advantage (see Fig. 89). 



Fifth, after big limbs are pruned off, decay often sets in 

 at the wound. This decay may be prevented by coating 

 the cut surface with paint, tar, or some other substance 

 that will not allow spores to enter the wounded place or 

 to germinate there. Many a tree could be saved by this 

 precaution. 



Sixth, it frequently happens that the spore or fungus 

 remains in the soil. This is true in the cotton wilt, and the 

 remedy is to so rotate crops that the diseased land is not used 

 again for this crop until the spores or fungi have died. 



SECTION XXVIII SOME SPECIAL PLANT DISEASES 



Fire Blight of the Pear and Apple. You have perhaps 

 heard your father speak of the "fire blight" of the pear 

 and apple trees. This is one of the most injurious and 

 most widely known of fruit diseases. Do you want to 

 know the cause of this disease and how to prevent it ? 



