GRASSES OP IOWA. 



291 



Fig. 137. Sorghum blight (.Bacillus sorghi); a,lea.t and sheath affected; 5, young 

 affected plant; c, rod-shaped bacilli. (Kellerman and Swingle.) 



Treatment. — Burrill and Kellerman have shown that soil 

 upon which sorghum has been grown contains the organism 

 and that they occur in old stubble. It has also been noted that 

 since sorghum fields are not burned over, the disease is on the 

 increase. It would certainly seem advisable to burn over old 

 fields. But this will not prove sufficient, since the fungus 

 occurs in the soil. Many fungus and insect enemies can be 

 checked very materially hy rotation of crops. In either case 

 we cannot expect to remove the disease entirely, since it occurs 

 where sorghum has never been grown. It is probable that the 

 micro-organism is carried through the air atid water, as well as 

 the soil. 



GUMMING OF SUGAR CANE. 



In 1893 N. A. Cobb,* New South Wales, gave a full account 

 of the disease in sugar cane which caused a gumming; this he 

 attributed to Bacillus vascularum. The disease seems to have 

 been present in Australia for a considerable length of time, the 

 cane planters having been familiar with a disease characterized 



*Ag. Gazette. N.S.Wales. 4: 



