Chapter XIX. 



Diseases of Garden Crops. 



Orange- or red-rust of raspberries and blackberries [Gyw- 

 noconia inter stitialis (Schlcct.) Lagh.]. This rust is chiefly known 

 on account of the destruction occasioned by the cluster-cup 



stages, on the 

 raspberries, 

 blackberries and 

 their allies. The 

 cluster-cup stage 

 differs from that 

 of most of our 

 common rusts by 

 the absence of a 

 cluster-cup wall, 

 so that the chains 

 of spores are 

 spread out on the 

 surface of the 

 leaves. These 

 spores are pro- 

 duced in great 

 numbers in early 

 summer and late 

 spring and form 

 what is common- 

 ly known as the 



Fig. ]60. — Orange rust of raspberry and blackberry; to the 

 right on a leaf of wild blackberry; to the left a normal 

 unattacked leaflet. Original. 



orange rust. The 



rust is produced 

 on the under sur- 

 face of the leaf, and wild and cultivated raspberries, dew- 

 berries and blackberries suffer. The spores fall in a dense 

 orange powder. From golden orange, the lower surface of 



