66 THE RUSTS OF GRAINS IN THE UNITED STATES. 



Growth was slow and the heading period was delayed and length- 

 ened. The low night temperatures with abundant dews remaining 

 late in the morning were most favorable for spore germination and 

 infection of the growing grain, and a severe rust attack was the 

 result. That rusts were also severe in parts of South Dakota and 

 North Dakota in 1905 was to be expected from the low temperatures 

 that also prevailed during that year in those States throughout the 

 growing and heading period. 



PREVENTION OF RUSTS. 



In view of the almost universal distribution of rusts, the great 

 variety of rust forms, their complicated life histories and relation- 

 ships, the ease with which they are distributed, the apparent absence 

 of any weak point in their life history, and the great influence of 

 climatological conditions upon their development, it would seem that 

 there is but little chance to control these fungi or to prevent losses 

 caused by them from year to year. The worker on rusts from an 

 economic standpoint has kept persistently at it, however, and inves- 

 tigations along many lines have been made, a few of which seem to 

 give some promise of success in the future. Three main lines of 

 experimentation have been pursued. These are (1) experiments in 

 spraying, (2) experiments with soil treatments, and (3) experiments 

 in the selection and breeding of varieties resistant to the disease. A 

 comprehensive survey and treatment of these subjects must be 

 reserved for the future, but a few of the more important points will 

 be mentioned. 



SPRAYING EXPERIMENTS. 



Some of the first spraying experiments for rust prevention in tins 

 country were made by Kellerman and Swingle, in Kansas, in 1891 

 (61, p. 90). Two varieties of spring wheat, Fife and Bluestem, six 

 varieties of barley, and one variety of oats were used in the experi- 

 ment. The fungicides employed were flowers of sulphur, potassium 

 sulphid, chlorid of iron, and Bordeaux mixture. Spraying was 

 begun when the plants were 2 to 3 inches high and was repeated 

 every eight days, on an average, for 11 successive times. Rains 

 were unusually abundant during the season. Rust appeared plenti- 

 fully on the sprayed plats and apparently no beneficial results fol- 

 lowed the application of the fungicides. Pammel (82, p. 329) made 

 similar experiments with ammoniacal carbonate of copper and Bor- 

 deaux mixture. Three applications were made, but were " entirely 

 useless." Galloway (53, p. 198), in 1891-92, performed spraying 

 experiments at Garrett Park, Md. He used a variety of spraying 

 solutions, among which were Bordeaux mixture, ammoniacal copper 

 carbonate, ferrous ferrocyanid, copper borate, ferric chlorid, ferrous 



216 



