64 BULLETIN 981, U. S. DEPARTMENT OF AGRICULTURE. 
(Contrarinia (Diplosis) sorghicola Coq.) usuaily prevents the profitable 
production of Sudan grass seed in the Southern States east of central 
Texas. 
The diseases and insect enemies of Sudan grass and methods for 
their control are discussed in Farmers’ Bulletin 1126, entitled ‘‘Sudan 
Grass.’ A full account of the insects which attack Sudan erass is 
given in Circular No. 7 (new series) of the Texas Agricultural Experi- 
ment Station (17). 
WEEDS. 
There are but few weeds which cause any considerable trouble in 
Sudan grass fields. ‘The preparation of the seed bed usually destroys 
the spring crop of weeds, and if the soil is warm the grass starts off 
quickly and grows so rapidly that as a rule weeds are not able to com- 
pete with it. Sudan grass probably ranks next to millet in its ability 
to overcome weeds. 
The common weeds, such as the pigweeds, Russian thistle, foxtail, 
and the sand burs, are sometimes found in fields of Sudan grass. 
They rarely occur in sufficient numbers, however, to affect the yield 
of hay. The worst weed pest is undoubtedly Johnson grass, which 
behaves as a perennial south of the thirty-eighth parallel of north 
latitude and is widely distributed on the better soils of that region. 
Its relation to the seed production of Sudan grass has ooea discussed 
under that topic. 
The presence of Johnson grass in a field of Sudan grass being cut 
for hay is of little consequence except for the very slight reduction 
in yield that it entails. The quality of the hay when Sudan grass is 
mixed with Johnson grass is fully as good as that of Sudan grass alone. 
The immediate effect, therefore, of Johnson grass in Sudan grass fields 
is not especially objectionable, but the aggressive rootstocks of 
Johnson grass make it difficult to eradicate and cause it to persist 
and interfere with the following crop. The succeeding crop, espe- 
cially if it is corn or cotton, will be injured appreciably by the Johnson 
grass, and this fact causes farmers to resist its incursion into any of 
their cultivated fields. Because of its tendency to persist on the land 
after another crop has replaced the Sudan grass, extreme care should 
be exercised by the farmer to avoid introducing Johnson grass in the 
Sudan grass seed with which he plants his fields. 
SUMMARY. 
The value of the 1918 crop of Sudan grass in the United States was 
estimated at $10,500,000. Practically all this crop was derived from 
the 8 ounces of seed obtained in 1909 by the United States Depart- 
ment of Agriculture from R. Hewison, Director of Agriculture and 
Lands, Sudan, Africa. 
