66 BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. 
Seed production at present is very often unprofitable on account of 
low yields and uncertainty as to price. Seed yields are highest in 
western Texas and the irrigated. regions of New Mexico, Arizona, 
and California. 
The greatest difficulty attending the production of Sudan grass 
seed is the danger of the admixture of Johnson grass seed. Ex- 
treme care is required to prevent such mixtures, because it is practi- 
cally impossible to separate the seed of the two grasses by mechani- 
cal means. 
A method of identifying the seed of Johnson grass when mixed 
with Sudan grass has been developed and described by F. H. Hill- 
man (11), of the United States Department of Agriculture. 
Great care is necessary In growing Sudan grass for seed to prevent 
its hybridization with the sorghums. Sudan grass intended for seed 
production should never be sown on a field which has produced 
sorghum the previous year, and the field ought to be situated at 
lone 80 rods from any field of sorghum. 
The same diseases and insects that attack sorghums also injure 
Sudan grass. The most important diseases are red-spot and kernel 
smut; the most destructive insects are grasshoppers, chinch bugs, 
and the sorghum midge. 
