GRASSES OF IOWA. 289 



"S'Sjl.r^wtiA. 



Ml 



Fig. 136. Corn wilt. Longitudlual section of maize stem showing a mass of bacteria 

 In the large ducts. (Stewart, Geneva, N. Y., Agrl. Exp. Sta.) 



plant at any stage of growth, but is most injurious when the 

 ears are forming. The disease is scattered through the field, 

 diseased plants frequently occurring in the same hill with 

 healthy ones. It is also found on various kinds of soil, but it 

 seems to prefer the early dwarf varieties of corn, like the Man- 

 hattan. Stewart further states that certain varieties are more 

 severely affected than others. It was first observed at Queens, 

 N. Y., where it has beea known for three years. Occasionally 

 an entire crop has been ruined and a loss of from 20 to 40 per 

 cent has been frequent. This disease seems to only affect the 

 sweet corn. Field corn and pop corn are entirely exempt. 



Stewart* thinks the organism is not only disseminated by 

 the seed, but may also be spread by manure and implements. 

 To prevent this disease use care in selecting the seed. Plant 

 resistant varieties. 



Quite recently Dr. Erwin P. Smithf has investigated this 

 disease and naijied the organism Pseudomonas Stewartii. 



SORGHUM BLIGHT. 



Related to the diseases above is what is known as sorghum 

 blight {Bacillus sorghi Burrill.) 



Burrillt fi.rst described sorghum" blight, and the organism 

 which causes the disease. Kellerman and Swinglet have 



*Bull. N. Y. Agrl. Exp. Sta. Geneva. 130: 423. 

 tProc. Am. Ass. Adv. Sci. 47: 422. 1898. 



i^Barrill. A disease of broom-corn and sorghum. Proc. Soc. Promotion of Agrl. Sol, 

 8: 30. The Microscope, 7: No. 11. 1887. 



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