SUMMARY. 73 



subject to drought; and for rust resistance, on ground where a rust 

 epidemic can be insured. In the case of rust these conditions can be 

 promoted in several ways: (1) By keeping the breechng phits on fairly 

 low ground, where moisture is plentiful but not excessive and where 

 dews remain as long as possible; (2) by planting barberries around or 

 through the ])lats when breeding for resistance to Puccinia graminis, 

 or by planting buckthorns when breeding for resistance to P. coro- 

 nata; (3) by planting winter grains at intervals through the plat 

 where spring grains are being bred (since the rusts, as a rule, occur 

 earlier on the winter than on the spring grains) ; (4) and most impor- 

 tant, by collecting secidio or uredospores in water and spraying on 

 the plants with hand or knapsack sprayers during the evenings at the 

 period when the grains are most susceptible. All of these methods, 

 or modifications of them, are now in use by BoUey (25, p. 48; 27, pp. 

 177-182), in North Dakota; by Biff en, in England (16, p. 112), at 

 the Cawnpore Agricultural Experiment Station, in India (55, pp. 

 54-57); and have been employed since 1907 by the Office of Grain 

 Investigations in cooperation with the Minnesota Agricultural 

 Experiment Station. In Minnesota the authors have established a 

 plat where a very virulent rust attack was obtained, even in the sea- 

 son of 1909, in which no stem rust appeared in any of the fields in its 

 vicinity and in which only local infections were reported throughout 

 the spring-wheat States. 



Breeding of this kmd is extremely important and should be carried 

 on by agronomists and plant pathologists at every experiment sta- 

 tion where conditions are such that rust epidemics may occur at any 

 time. To be effective, it must be extensive and must be persistently 

 employed. 



SUMMARY. 



(1) Rusts are among the most serious diseases of grains in the 

 United States, causing an estimated annual loss of fifteen to twenty 

 million dollars. In 1904, in the three States, Mnnesota, North 

 Dakota, and South Dakota, the loss due to rusts, conservatively esti- 

 mated, was as high as $10,000,000. 



Tliis paper deals only vAi\\ the rusts of the small-grain crops, wheat, 

 rye, oats, and barley, including Puccinia graminis, P. ruhigo-vera 

 tritici, P. ruhigo-vera secalis, P. coronata, and P. simplex. 



(2) Practically all these rusts are coextensive \vith their hosts in 

 the United States, but arc not serious in all localities. In general, the 

 areas most affected are the valley of the Mississippi and its tributaries 

 and certain coastal areas. In some years even the drier areas may be 

 affected. 



The stem rust of wheat is of great importance in the hard winter 

 and the hard spring wheat belts, is frequent in Washington and Oregon, 



216 



