240 



AGRICULTURE ON THE PACIFIC SLOPE 



kind of grain as a rule cannot infect another kind of 



grain. 

 There are also other kinds of rusts which attack grain 



(such as the orange leaf -rust of wheat and rye and the 



crown rust of oats), which form their cluster cups on 



plants other than the barberry. 

 The yearly loss from grain rust in the United States 



is more than eighteen million dollars. 



In threshing grain the red spores of rust gather in 



various parts of 

 the machine and 

 may sometimes be 

 gathered up by the 

 pint. 



Asparagus rust. 

 Asparagus rust (fig- 

 ure 138), which has 

 caused great dam- 

 age in the past, has 

 been found to dis- 

 appear entirely, if 

 the plants are 

 dusted with dry 

 sulphur while the 

 dew is on them. 



FIG. 139. Rust on rose leaf. . ^ 



If there is not suffi- 

 cient dew on the plants to make the sulphur stick, they 

 must be sprayed with whale-oil soap before using the 



