92 BOARD OF AGRICULTUEE. [Pub. Doc. 



etc., which arc resistant to disease. I am convinced that in 

 recent years we have limited ourselves too exclusively to the 

 selection of varieties along the line of fruitage. The result 

 has been a serious impairment of the constitutional vigor and 

 the resistant qualities of the stock. To my mind, this is one 

 explanation of the surprising increase of fungous diseases 

 during the past few years. 



Finally, the judicious use of chemical fertilizers has an 

 appreciable effect upon the prevalence of fungous diseases, 

 both directly and indirectly. It is a well-known fact that 

 the fungus causing the " scab" of potatoes is able to live and 

 thrive in the manure heap. Scabby potatoes fed to stock 

 account for its presence there, whence it is carried directly 

 to the seed potatoes. The use of chemical fertilizers evi- 

 dently offers a means of preventing infection from this source. 

 Moreover, the tendency of highly nitrogenous fertilizers is 

 to produce a soft, succulent, ill-ripened growth, which suc- 

 cumbs readily to the attacks of fungi. It is evidently advis- 

 able to balance this tendency by the use of fertilizers rich in 

 potash and phosphoric acid, whereby firm, resistant tissues 

 are secured. 



I Ijelieve that these hygienic and cultural methods of deal- 

 ing with fungous diseases are deserving of far more attention 

 than they usually receive on the part of men who are farm- 

 ing for profit, and that in many instances practical immunity 

 can be secured by them without the labor and expense of 

 spraying. I should, however, belie my own experience were 

 I to detract from the value of fungicides intelligently used. 

 The case is much the same as with human beings. Ordinarily 

 a person can maintain a condition of sound health so long as 

 he obeys a few definite principles of hygiene, and keeps his 

 surroundings in a clean and sanitary condition. Neverthe- 

 less, occasions will arise, owing perhaps to some constitu- 

 tional weakness or to the sporadic appearance of a specific 

 disease, when recourse must be had to medical treatment. 

 So it is in the case of vegetable pathology, and nowadays 

 facilities for spraying with fungicides have become an essen- 

 tial feature of farm and orchard practice. 



For convenience, we may divide fungicides into three 

 classes, — liquids, powders and vapors. Of these, the first 



