8 CEREAL RUSTS OF THE UNITED STATES. 



Bordeaux mixture, ferric chloride, i)otassium bichromate, mercuric chlo- 

 ride, and perhaps one or two other compounds are quite effective in 

 checking the spread of rust, yet, unless some great improvement is 

 made in the method of applying fungicides, it would be practically 

 impossible to spray a field of grain, owing to the great trouble in reach- 

 ing all portions of the plants, and the difficulty, if not impossibility, of 

 using any suitable kind of spraying apparatus in the field without 

 destroying much of the grain. Besides, the expense of spraying large 

 fields is an obstacle. 



In Australia^, as above stated, the careful and widespread attention 

 given to the wheat-rust problem has resolved itself almost wholly into 

 a study of rust-resistant varieties. McAlpine, Shelton, Pearson, and 

 others have contributed much to the knowledge of rust-resistant varie- 

 ties, but most of the work in this line has been done by Dr. N. A. Cobb 

 as vegetable pathologist to the government of New South Wales, and 

 William Farrer, a private breeder of rust-resistant varieties of wheat. 

 An important concomitant result of the work in Australia is that the 

 country now has wheat varieties that are vigorous, true to name, and 

 of exceptional quality for the particular region in which they are grown. 



Aside from the series of experiments reported in this bulletin, no 

 systematic study of rust resistance has been made in this country, 

 though from time to time observations in this Hue have been recorded 

 by experiment station workers. Bolley (7, pp. 15, 10) refers to such 

 observations made as far back as 1889, and farmers have long known 

 that occasionally certain varieties of cereals are more exempt from 

 rust than others. But in all such investigations as just mentioned the 

 study of the rust itself is practically ignored, and hence much of the 

 experimental work in spraying and selection of varieties is likely to be 

 done blindly or needlessly and lead to unreliable conclusions. There 

 would obviously be no necessity for combating a cereal rust every 

 season if by knowing its life history it could be prevented from getting 

 a start. Moreover, spraying experiments that prove successful in one 

 season or in some certain locality may be an entire failure another sea- 

 son or in another locality, simply because different rusts are being 

 treated in the different instances. So, also, it has been thoroughly 

 demonstrated, as will be discussed further on, that certain varieties of 

 wheat and oats are capable of the greatest variation in their powers of 

 resisting rust, this resistance varying according to the kind of rust, the 

 locality, and the season. 



In the course of investigations reported by Hitchcock and the writer, 

 the necessity of studying the physiological relationships of the rusts 

 and the manner in which they winter over became more and more evi- 



' The results of the Australian investigations were published in a series of reports 

 of intercolonial wheat-rust conferences extending from 1890 to 1896^^ and also in the 

 Agricultural Gazette of New South Wales and various special reports of different 

 colonies. 



