damage to sugar cane grown for sirup’than to the highly resistant 
varieties used in sugar production. In Mississippi, Alabama, 
Georgia, and northern Florida, sugar cane grown for sirup is subject 
to the same diseases that affect the sugar cane grown for sugar. 
The significance of ratoon stunting disease with sugar cane growm 
for sirup has not yet been appraised. 
Tobacco 
At least five groups of parasitic diseases cause serious losses 
to the tobacco crop -= root rots, leaf spots, mosaic and other 
virus diseases, blue mold, and black shank. 
The root rots reduce plant growth in every area. It is estimated 
that 50 percent control could be obtained if growers would use 
resistant varieties, proper rotations, and fumigation. Invasion 
of the leaves by the leaf spot parasites causes reduction in yield 
and affects the quality. At present not over 10 percent control is 
possible by use of fungicides. However, varieties immune from wild- 
fire, one of the most important organisms of this group, are being 
developed. The virus diseases are prevalent in all areas, always 
retarding and reducing yields and quality of cured leaf. Probably 
25 percent control would result from more general use of sanitary 
methods, Ultimate control appears to be through the use of resistant 
varieties which are being developed. Blue mold causes a shortage of 
transplants, delay in planting, and resultant poor stands. It com- 
monly occurs in seedbeds each year and can be controlled by timely 
and thorough use of fungicides. The black shank disease appears to 
be on the increase, and control measures tend to become less effec- 
tive. It kills the plants through root invasion and persists once 
the soil is infected. Some control is accomplished by use of rota- 
tion and resistant varieties. 
A group of miscellaneous diseases occur in wide areas and occasion~ 
ally cause some damage. Bacterial wilt and fusarium wilt are being 
controlled by use of resistant varieties. No effective control 
measures for sore shin and southern stem rot have been developed. 
Curing decays occur during August and September when humidity often 
becomes excessive while the tobacco is in the curing barns, Storage 
damage may take place when the packed tobacco contains excessive 
moisture. Temperature and moisture control offer an effective 
method to prevent these losses, but it is not always feasible to 
apply then. 
Wheat 
All the diseases of wheat reduce the yield, and some, such as stem 
rust, mildew, Septoria, mosaic, and the root and foot rots, also 
cause a shriveling of the grain with further loss in milling value. 
Spores of bunt or stinking smut are retained on the seed in threshing 
and, since they have an undesirable odor, such grain must be washed 
before milling. The rusts, Septoria, root and foot rots, and virus 
236 
