90 BOARD OF AGRICULTURE. [Pub. Doc. 



finally, they may be wholly external, producing no change 

 whatever in the tissues, but causing a diseased condition of 

 the whole leaf attacked, by cutting off the free supply of air 

 and by absorbing the juices from the external tissues. 



All these facts must be studied before we are prepared to 

 recommend any definite line of treatment. Having, how- 

 ever, ascertained the cause of a certain disease to be a specific 

 parasitic fungus, and having observed the location of the 

 parasite, its course of development and its methods of repro- 

 duction, we can with a fair degree of assurance take measures 

 to prevent it. I purposely use the word " prevent " rather 

 than "cure," for, while we can prevent the inception or the 

 recurrence of a disease with a fair degree of certainty, it is 

 almost impossible to cure it, after the fungus has become 

 established within the tissues, by any means short of the 

 destruction of the parts affected. 



There are two definite lines of treatment of fungous dis- 

 eases : the one hygienic, aiming to eradicate disease by the 

 alteration of external conditions conducive to its spread ; the 

 other consisting in the application, to the parts endangered, 

 of some substance inimical to fungous growth.' 



Enough has been said regarding the nature and life history 

 of fungi to show you that if we can destroy both the spores 

 and the vegetative threads of a fungus, while those organs 

 are either dormant or have not yet reached maturity, we shall 

 get at the root of the whole matter. Here a little common- 

 sense is of great assistance. Fruit rots and ftdls prematurely, 

 usually because it has been attacked by a parasitic fungus ; 

 the same agency causes leaves to blight and fall from the trees. 

 Such fruit and leaves are allowed to remain where they fall, 

 because they are of no use. But the fungus within their tissues 

 remains protected during the winter, develops slowly, and, 

 with the approach of warm weather, produces its spores in vast 

 numbers, each spore able to reproduce the fungus upon the 

 budding leaves and young fruit of the tree immediately above 

 it, if a slight breeze should cause it to lodge there. No pre- 

 ventive treatment of any nature in spring or summer will 

 protect completely fruit and leaves so wantonly exposed to 

 disease. If the rotten fruit be not allowed to remain where 

 it falls, it is usually fed to the pigs. The spores of the 



