Colorado Plant Diseases 
47 
CEREALS 
The diseases affecting the various cereals are more or less similar 
and therefore are discussed as a group. 
Smuts (40), (48), (50), (51) — The smuts of cereals are perhax)s 
the most destructive of all plant diseases. They were responsible for 
a loss of nearly 135,000,000 bushels of grain in the United States in 
1917. The loss in Colorado alone was almost 2,000,000 bushels. 
The smut affecting one kind of plant is so specialized that it 
cannot grow on any other species of plant. Each cereal has its own 
smut or smuts which can affect that cereal and no other. 
CORN 
Corn Smut (Ustilage zeae) — There is only one smut of impor- 
tance alfecting corn. It is very common in Colorado and is the source 
of much loss. 
Large black smut masses are formed on 
any part of the corn plant above ground in- 
cluding ears, stems, leaves, and tassels. Mil- 
lions of spores are contained in these smut 
masses and are scattered broadcast by the 
wind. Each of these spores which may live 
over the winter in the soil, germinates in 
the spring and forms dozens of still smaller 
spores that are easily blown about by the 
wind. These secondary spores may infect 
any part of the corn plant and cause a new 
mass of spores. 
For obvious reasons seed treatment is 
not effective in controlling corn smut. It 
has been shown that smut spores may pass 
through the digestive tracts of animals un- 
injured. Furthermore such spores germinate 
in manure piles which form ideal places for 
the production of the secondary spores in 
great quantities. It is plain therefore that 
smutted corn should be fed to animals and 
only rotted manure should be placed on corn 
fields. Since the spores may live in the soil, 
crop rotation is advisable. 
BARLEY 
Covered Smut (Ustilago hordei) — This is the most common and 
destructive of the two smuts affecting barley. Fields often contain 
