398 DISEASES OF ECONOMIC PLANTS 



long, narrow, or elliptical spots are formed, frequently 

 with a dull, purple border, and usually with a white 

 center. When on the pods, they are obliquely situated. 

 When old, they appear as black, oblique lines. 

 No serious damage has been reported. 



FIBER PLANTS 

 COTTON 



Wilt, fusariose (Fusarium vasinjedurn Atk.). — The cot- 

 ton wilt, now widely distributed and yearly preempting 

 more territory, is caused by a fungus that plugs the water 

 ducts in the veins of the stem and cuts off the water 

 supply to the parts above, always reducing the vigor of the 

 plants and usually resulting in speedy death. 



Soil which produces a sick crop one year is so infested 

 with the causal fungus as to insure reappearance of the 

 disease in more extensive areas in subsequent croppings 

 with the susceptible plant. The destruction of this form 

 of disease, which takes not only the crop, but in part the 

 usefulness of the soil as well, cannot be estimated. Its 

 injury can only be reahzed by those who have experienced 

 its effects. 



Wilt has long been known by southern cotton planters, 

 and is now prevalent in many sections of Alabama, Arkan- 

 sas, North Carolina, South Carolina, Georgia, Louisiana, 

 and probably throughout the whole cotton belt. Many 

 foreign countries also record it. 



The first appearance of the wilt is a yellowing of the 

 lower leaves at the edges or between the main ribs, which 

 portions may become almost white ; later they turn brown 



