CHAPTER X 



FUNGICIDES AND SPRAYING APPARATUS 



A FUNGICIDE is any substance which will destroy or 

 prevent the growth of the spores or the mycelium of 

 fungi. They are usually used only against fungi which 

 cause diseases, especially those which cause the diseases 

 of plants, but they are also used to prevent the decay 

 of timbers. They must be of such a character as to 

 destroy or hold in check the injurious parasites, and at 

 the same time not be injurious to the host plants, nor 

 prove injurious to human beings or lower animals which 

 may use the plants for food. The fungicide must also 

 be of such character as will not discolour or injure the 

 beauty of fruits and vegetables, and thus reduce the 

 market value. It must be remembered that the market 

 value of many plant products depends fully as much 

 upon the appeal to the eye as to the palate. 



Since the fungicide must be harmless to the host 

 plant, it is self-evident that it will be most effective 

 when used against those organisms which are confined 

 to the surface of the plant. But since the internal 

 parasites must come to the surface of the host plant to 

 produce their spores, the fungicide can be used to 

 destroy the spores as rapidly as formed, and thus prevent 

 their spread to the neighbouring plants and to other 

 parts of the same plant. It can also be used to prevent 

 the germination of the spores on the surface of healthy 

 plants. 



The time and number of applications must depend 

 upon the character of the host plant, character and life- 



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