POTATO DISEASES 



439 



els; while the average quantity imported during the same 

 years was 2,300,000 bushels. 



575. Blight. The more prevalent diseases are blight, 

 scab, and internal brown rot. Blight appears in two forms, 

 the early and the late. Early blight attacks the leaves of 

 the potato plants early in the season, and gradually spreads 



Fig. 136. Spraying to prevent disease and insect injury is an important part 

 of modern potato growing. 



until the entire plant is killed. It is usually first seen as 

 dark spots on the leaves. Late blight attacks the plants in 

 a somewhat similar manner, but considerably later in the 

 season. It first affects the plants near the ground and 

 spreads rapidly upward; the diseased parts quickly turn 



