105 



injuries. These, though not perhaps distinctive diseases, are, 

 nevertheless, troubles which every orchardist is forced to deal 

 with more or less. It is not, however, the purpose of this 

 chapter to discuss these troubles. They are, for the most part, 

 closely associated with orchard management or mismanage- 

 ment, and through proper attention to all of the many details 

 of orchard management their occurrence may be reduced to 

 an inconsequential minimum. 



General Control Measures. 



Spraying the apple orchard with fungicides or with fungi- 

 cides and insecticides combined is absolutely necessary for the 

 production of clean, sound fruit. Spraying, however, is not a 

 panacea for all the diseases to which the apple is heir. Neither 

 will spraying" cure a disease. The object of applying a fungi- 

 cide is, rather, to prevent or control disease by killing or in- 

 hibiting the development of parasitic fungi. To be effective, 

 therefore, the spraying schedule must be based on knowledge 

 of the life histories of the fungi to be combated. It is an 

 important function of the plant pathologist to work out life 

 histories of these parasitic organisms, and find out, if he can, 

 the vulnerable points in the different stages of their develop-; 

 ment. With this accomplished for any disease, it is then 

 usually possible to work out an effective spray schedule. On 

 such knowledge are all control measures based, and the spray 

 schedule given in another section of this publication is the result, 

 of such fundamental work by the scientist. Obviously, physi- 

 ological diseases are not much affected by spraying. 



In addition to spraying, general orchard and storage sani- 

 tation, regulation of conditions and approved cultural and 

 other management details must be practiced in order to as- 

 sure a satisfactory product. Where combative measures other 

 than spraying are necessary, they are discussed in connection 

 with specific diseases. 



Directions for spraying are given in the "Spray Schedule 

 for the Apple" (page 113) and for preparing fungicides in the 

 chapter on "Insecticides and Fungicides for the Apple" 

 (page 106). 



