384 
SOME GENERAL PLANT PROBLEMS 
Control of the Disease. — As the result of many experiments 
with disinfection, fertilizers, resistant varieties, and so forth, 
the best means of control seems to 
be to destroy or boil all potatoes 
grown on such infested land, to 
establish a strict quarantine to 
prevent its spread, and to practice 
rotation of crops over the period 
of eight years that the fungus is 
known to remain in the soil. It 
does not cause damage to any 
other cultivated crop, but it may 
propagate itself on other members 
of the potato family, especially 
such as grow wild. 
Courtesy of Experiment Station, 
University of Minnesota. JV 0^. AS an illustration Of the 
Figure 35^— Normal Grains application that may be made of 
biology, it may be said that the 
disease was first reported in this country by a biology 
University of Minnesota. 
Figure 352.—Grains of Wheat 
Affected by Black Rust. 
student in high school who had 
noticed potatoes in the field at 
home, but had not known the cause 
of the peculiar appearance or the 
seriousness of the disease till his 
teacher mentioned it in class. 
319. The Black Stem Rust of 
Grain and the Barberry. — The 
black stem rust of grain causes the 
loss of millions of bushels of grain 
every year. In 1916, a bad rust 
year, the loss in wheat alone in a 
single state, Minnesota, was about 
30,000,000 bushels. In 1917, not 
a bad rust year, the loss in the 
whole United States was about 14 
