DAMAGE CAUSED BY PLANT DISEASES 



The crop grower often suffers much damage from plant 

 diseases, entirely unconscious of the fact that his crop is 

 affected by disease. Or, if the presence of disease is recog- 

 nized, the amount of damage is often underestimated. Thus 

 the presence of oat smut to the extent of 15 or even 40 per 

 cent, is sometimes entirely overlooked by an otherwise ob- 

 servant man. 



An attitude of willful disbelief in the prevalence of a 

 disease is often couched in such terms as these: "I don't 

 see why I must work to protect my apples from rot. My 

 grandfather used to raise fine apples without any attention 

 to these things." 



It must be recognized that plant diseases are with us; 

 that they are increasing by importation from other coun- 

 tries or other states; that diseases formerly insignificant 

 are, in many instances, becoming serious; that long, inten- 

 sive culture of one crop in a locality permits new diseases 

 to develop. Diseases have many means of dispersal; on 

 seed, hay, or other produce shipped by mail, express, or 

 freight; on animals; by wind; by water; by birds. Diseases 

 will continue to spread and to increase in destructiveness 

 until the individual and the general public are aroused to 

 such active appreciation that conditions of plant sanitation 

 and plant protection become much more general and effective 

 than they now are. 



Conspicuous examples of the advent of diseases in coun- 

 tries where they were before unknown, are afforded by the 

 following: grape powdery-mildew, native to America and 

 first seen in Europe in 1845; the American gooseberry mildew, 

 first found in Europe in 1900; the potato late-blight, native 

 to South America, noted in Europe in 1830; the asparagus 

 rust, introduced from Europe about 1896; the hollyhock 

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