288 PLANT DISEASES 



again to the wheat plant. This method of living over 

 the winter will be seen to be independent of any bar- 

 berry plants. In short, the stem rust of wheat may live 

 over the winter in the summer stage and also in the 

 winter stage. The summer stage that lives over does 

 not need a barberry plant, while the winter stage does. 

 The wintering over of the summer stage is compara- 

 tively easy in our southern states, as, for instance, 

 Texas, where the winter is not so severe, but it is 

 also known to occur as far north as Minnesota and 

 North Dakota. 



In view of what has been said of their life history, 

 the possibilities and difficulties of combating rusts may 

 now be mentioned. Seed treatment, such as is com- 

 monly used for smut, has apparently no effect on 

 the rust; neither will the treatment of the soil assist in 

 any way, since the spores do not live over in the soil. 

 Even the burning of the straw with the black or winter 

 stage on it has not given any beneficial results, since 

 the summer stage can live over the winter on the wild 

 grasses or the summer spores may be blown up from the 

 south, where they can easily live over the winter on 

 winter wheats or wild grasses. Of the most common 

 methods for treating diseases which have been men- 

 tioned above, spraying is the only one left to consider. 

 The spraying of the fields of wheat is apparently an im- 

 practicable remedy. Moreover, the spraying of Bor- 

 deaux has neverbeen found to give very beneficial results. 

 Even if it were possible to prevent the disease by spray- 

 ing, it seems probable, from the nature of the crop and 

 the difficulty of covering such large areas as would 

 be necessary to cover, that the spraying of rust would 

 be impracticable. It has been necessary, therefore, 



