SORGHUMS 277 



Lima beans, Hyacinth beans, Guinea-grass and other 

 plants, it is quite certainly not due to a parasite. Poison- 

 ing has been most frequently reported when cattle were 

 pastured on second-growth sorghum, and on account of 

 the danger this is rarely advisable. A few cases of 

 poisoning by Johnson-grass are also recorded. 



332. Diseases. Three diseases cause more or less 

 damage to the sorghums ; namely, kernel smut (Sphace- 

 lotheca sorghi) ; head smut (Sphacelotheca reiliana) ; and 

 Red spot or Sorghum blight (Bacillus sorghi). 



Kernel smut affects only the individual grains, and all 

 or nearly all the seeds in a head are destroyed, but the 

 appearance of the head is but slightly changed. Kernel 

 smut may be controlled by treating the seed with formalin 

 or with hot water. 



Head smut destroys the entire head, which, as it emerges 

 from the sheath, is practically a mass of smut spores 

 covered with a whitish membrane. No satisfactory 

 treatment for this smut has yet been found. 



Red spot or blight causes characteristic red spots to 

 appear on the leaves and stems. When abundant the 

 leaves die prematurely. All varieties of sorghum and 

 Johnson-grass are subject to the disease, but by selection 

 strains that show a high degree of resistance may be secured. 



333. Insect pests. Only a few insects cause serious 

 damage to sorghums. The most important are the 

 sorghum midge, the chinch-bug, the corn-worm and the 

 fall army- worm. 



Sorghum midge (Diplosis sorghicola). It has long been 

 known that the sorghums seldom produced good seed 

 crops in southern Texas. The cause of this is the sorghum 

 midge, as first demonstrated by C. R. Ball in 1907. This 

 little fly lays its eggs in the flower when in bloom and 



