diseases may also cause a reduction in leaf area during the fall and 
winter with consequent loss in value for pasture. Losses from the 
rusts, smuts, mosaic, and mildew have been materially reduced by the 
development of resistant varieties. 
Leaf rust is the disease causing the largest average loss to the 
wheat crop for the country as a whole. It is present almost every 
year over most areas where wheat is grom except the drier sections 
of the West. 
Losses from stem rust are most frequent in the spring wheat areas 
of the North Central States, particularly North Dakota, South Dakota, 
and Minnesota. Local losses may occur in other areas. Damage is 
not consistent from year to year, as it depends on the presence of 
favorable weather, susceptible varieties, and an abundance of inoculum. 
Most of the epidemics of recent years have resulted from inoculum 
that has lived over winter on wheat in Mexico and southern Texas. 
Prior to 1918 losses arose largely from inoculum that was disseminated 
each spring from rust infections on barberry leaves. Since then a 
vigorous barberry-eradication program has been conducted in the 
principal grain-growing States. Stem rust losses at one time averaged 
50 million bushels annually, and during a single epidemic year 
amounted to as much as 200 million bushels. The average for the 
last 9 years has been about 15 million bushels. 
Loss from bunt is heaviest in the Pacific Northwest and Inter- 
mountain States, although occasional losses occur in scattered fields 
in other wheat-growing areas. Losses in the Pacific Northwest vary 
from year to year, depending on the use of resistant varieties, 
of seed treatment, and on weather and soil-moisture conditions at 
seeding time. Loose smut causes significant losses only in the more 
humid sections, particularly the eastern par+ of the soft winter 
wheat area and the eastern parts of the hard red winter and hard 
red spring wheat areas. Losses are rather consistent from year to 
ye aro 
Streak mosaic caused a loss of 7 percent of the Kansas wheat crop 
in 1949 and some loss in most years since 199. Some losses, usually 
small, occur in nearby States. Soil-borne mosaic causes slight 
lesses in Illinois, IMdiena, North Carolina, and nearby areas almost 
every year. 
Mildew and Septoria are present from Kansas and Texas eastward 
each year and may occasionally cause rather heavy losses in local 
areas. Scab sometimes causes losses when wheat follows corn if the 
cornstalks are not well covered or removed when the land is prepared. 
Forage Crops 
The loss estimates for forage crops have been restricted to those 
crops grown on land suitable for rotation farming. The losses in 
Table 2 are based principally on forage used for hay. tgsses in pastures 
and ranges attributable to diseases are reported in Chapter VI under the 
heading "Pastures ard Ranges." 
EC 
