GRASSES OF IOWA. 281 



cussed at considerable length by Eriksson and Henning under 

 the following heads: Heavy rains; sudden temperature changes; 

 wind and dew. 



The writers commenting on the subject concluded that the 

 developmentof black rust is highly favored by the large amount 

 of rain through July and early August. This favors a rapid 

 germination of the uredo spores The most favorable condi- 

 tions for the rapid development cf yellow rust for winter wheat 

 occurs in the month of April when there is a large precipita- 

 tion. 



. Eriksson and Henning have also made some experiments on 

 spraying to prevent rust. They tried such substances as sul- 

 phate copper, eauceleste, Bordeaux mixture, chloridaof iron 

 and sulphate of iron. It appears from these experiments that 

 spraying with Bordeaux mixture and eauceleste, somewhat 

 lessens the attacks of rust. 



Experiments made by Galloway* with fungicides, in which 

 seed, soil and plants were treated, showed that certain fungi- 

 cides, e. g. , Bordeaux mixture, potassium bichromate and some 

 others, were effective in checking rust to some degree, yet the 

 expense and method of treatment render it quite impossible to 

 spray the plants to prevent rust. The experiments by Keller - 

 man, Swinglef and the writerj also show that it is out of the 

 question to treat rusts. 



Eriksson and Henning, in the work quoted before, recom- 

 mend only to grow such varieties as are most resistant to this 

 disease. They state that this degree of resistance shows itself 

 to best advantage in years when there is considerable rust. 

 They recommend further that winter wheat be sown early 

 in the fall. In regard to oats, they recommend that the soil 

 should not be heavily fertilized; seed should be sown early in 

 the spring, that all barberry bushes and mahonia be removed, 

 and that weeds which harbor rust, like quack grass, should be 

 removed. 



Carleton§ states there is as yet no preventive for wheat 

 rust, at least so far as combating it directly. 

 Bacterial Diseases. 



The known diseases produced by bacteria are constantly 

 increasing. Hartig|| in his well known work on plant diseases 



*Rep. D. S. Dept of Agrl. 1893: 216. .Jour. Myc. 7: 95. 



+Bull. Kansas Agrl. Exp. Sta. 22. 



•4;Bull. Iowa Agrl. Exp. Sta. 16: 31. 



SlmprovemeQts In Wheat Culture. Yearbook U. S. Dept. Agrl. 1896: 497. 



IILerhbuch. d. Baumkrankhelten. 27. 1882. 



