FRUIT AND POTATO DISEASES 



trees free from the black knot. The wild clierries are affected 

 with the same disease, and must be attended to if the disease 

 is to be stamped out. 



DISEASES OF THE POTATO 



The potato is subiect to three serious diseases, viz., the early 

 blight^ the late blight, and the scab, all caused by parasitic 

 plants or fungi. As their names indicate, the two blights, or 

 rusts, as they are frequently called, differ in their time of ap- 

 pearance. The early blight may appear in June upon early 

 potatoes. Upon late potatoes it does not appear usually before 

 the middle or last of July. The late blight appears about the 

 first of August. Besides this difference in time of attack, the two 

 diseases possess distinct characteristics, which may be readily 

 made out by any one on a careful examination of the affected 

 vines. The early blight produces dark brown, sharply defined 

 spots upon the leaves, which increase in number and size until 

 the whole leaf may be destroyed. This disease does not attack 

 the tubers. The late blight is characterized by the rapid with- 

 ering and death of the leav'es, without the appearance of sharply 

 defined spots. It usually begins at the margins, and soon 

 involves the whole leaf. Upon the under side of the leaves, 

 along the line separating the dead from the living portion, may 

 be observed a whitish, mold-like growth, which the microscope 

 shows to consist of the spore stalks of the fungus plant which 

 is causing the trouble. This white mold, the absence of well- 

 defined spots, and the rapid dying of the leaves, serve to distin- 

 guish the late blight from the early. We frequently find vines 

 aftected with both diseases at the same time. The blights can 

 be successfully treated by spraying. 



The following are results obtained in treating potatoes for 

 early blight : 



Sprayed four times with i to lo Bordeaux mixture 



Unsprayed adjacent plot 



Sprayed twice witii i to lo Bordeaux . 



Unsprayed adjacent plot 



Sprayed three times with i to lo Bordeaux . 



Unsprayed adjacent plot 



Sprayed three times with i to lo Bordeaux . 

 Unsprayed adjacent plot 



