percent. The diseases also lower the value and quality of the grain 
and fodder and increase the cost of harvesting when they cause the 
crop to lodge. In this-country corn is subject to about 25 diseases. 
They attack all parts of the plant-~ears, leaves, stalks, and roots—- 
at various stages of development. Average losses for the 10-year 
period 192-1951 amount to about .8 percent in yield and 0.) percent 
in quality. On the basis of the average farm value of the crop for 
the same 10 years, this loss amounts to about $227 million each year. 
Losses vary in different sections of the country, being greatest in 
the more humid sections of the South. 
The major diseases of corn are diplodia stalk rot, diplodia ear 
rot, fusarium ear rot, northern corn leaf blight, southern corn leaf 
blight, Stewart's wilt, and smut. The two diplodia rots are wide- 
spread over most of the Corn Belt and the eastern part of the United 
States. Fusarium ear rot is a common disease, but often most destruc- 
tive in the drier areas, Northern corn leaf blight is generally 
found from Illinois eastward to the Atlantic coast. It becomes 
severe when the growing season is cool and dews are abundant. This 
disease was destructive in 193 and especially in 1951. Southern 
corn leaf blight extends generally from the Ohio River Valley south- 
ward. The disease thrives when dews are heavy, but it is favored by 
higher temperatures than northern corn leaf blight. Stewart's wilt 
is most severe on sweet corn, but it may cause appreciable leaf 
killing on dent corn in some years. It is found chiefly in the 
central part of the United States from Illinois eastward. Its preva- 
lence and severity increase in growing seasons preceded by mild 
winters, because such conditions favor the survival of large popula-~ 
tions of the corn flea beetle, the vector of the disease. Smut is 
Widespread, but is often most prevalent in the drier areas. The 
incidence of smut in the eastern half of the country was unusually 
high in 1945 and 1952. 
Frequently one or more of the minor diseases of corn may become 
destructive in localized areas. Charcoal rot, for example, has been 
known to cause appreciable injury to the stalks in some western parts 
of the Corn Belt. 
Cotton 
On cotton several of the disease organisms attack the plants at 
various stages of development, with correspondingly different mani- 
festations. 
Seedling diseases are caused by a complex of seed=borne and soil- 
borne organisms. Losses occur across the entire Cotton Belt, but 
are greatest in the Southeast. Periods of cool,damp weather follow- 
ing planting are especially conducive to losses, which may involve 
the entire stand. Seedling diseases account for 25-30 percent of 
the annual disease loss in cotton, The cost of replanting represents 
only a fraction of the potential loss, inasmuch as replanted cotton 
may also be damaged from insect attack and from weed competition. 
sec es, 
