potash, and four times as much water as a wall-developed oat plant, 
Common ragweed has a water requirement three times that of corn. 
Weeds increase the cost of labor and equipment and impair the 
quality of farm products. Special equipment, such as tillage 
implements, mowers, sprayers, and burners,is required for weed con= 
trol. Expensive seed-cleaning equipment in commercial sead houses 
is an additional cost made necessary by weeds. 
During a heyear period in Minnesota, North Dakota, South Dakota, 
and Mentana the wheat crop contained 7 percent of dockage (largely 
wsei seeds), or 360,900 tons annually. Flaxseed had an average 
annual dockage of 16 percent. At wheat prices of $2 per bushel, 
the farmers in these four Statas lost $2h million annually due to 
weeds after harvest alone. 
Weeds harbor insect and fungus diseases that attack crop plmts. 
Certain weedy mustards harbor the fungus that causes clubroot in 
cabbage. The fungus causing downy mildew of lettuce lives on 
prickly lettuce and sowthistle. These two weeds also harbor bean 
thrins. 
Weeds also cause depreciation of land values and reduce farm loans. 
The loss of $1,789,175,000 on cropland shown in Tables 9 and 10 is 
based on a reduction in value of the potential crop of $5 per acre, 
or about 10.2 percent. On pasture and grazing land the loss of 
$4:71,510,000 is slightly over 6 cents per acre. The cost of weed 
control on agricultural land has been estimated at #2,/86,251,900, 
or 7.) percent of the value of the crops. This estimate amounts to 
approximately $1.15 per acre. The total estimate of $3,71:7,936,009 
does not include the cost of weed control on nonagriculitural land, 
such as railroad, highway, utility rights-of-way, and industrial 
and military installations. 
Pastures and Ranges 
Diseases 
The Great Plains. Many different grasses comprise the vegetation 
of the Great Plains. The predominant species are native short 
grasses, such as the gramas and buffalo grass. The wild-ryes and 
wheatgrasses are also common. Some of these species are susceptible 
to and sometimes heavily attacked by stem rusts, leaf rusts, and 
smuts. Powdery mildew sometimes occurs abundantly on the wheatgrasses 
of the northern Great Plains, and nearly all the species are attacked 
by leaf spot famgi. The greatest damage, however, probably results 
from root rots and seedling blights. 
Northern Mountain-Intermountain region. Forage species of this 
region consist mainly of bromegrasses, fescues, wheatgrasses, #ni 
