176 Diseases of Greenhouse Crops 



Diseases of the Rhubarb 



The Rhubarb is considered a very hardy plant. It 

 is subject to but few diseases. 



Powdery Mildew 



Caused by Peronospora jaapiana Mag. 



This disease is fairly prevalent in Europe. Its 

 presence in the United States is not definitely known. 

 At any rate it is of little economic importance. 



Rust 



Caused by Puccinia phragmitis Schum. 



Rust is a disease of little consequence. The 

 secium known as Mcidium ruhellum occurs on the 

 rhubarb. The uredinia and the telia are found on 

 Phragmitis. By destroying the Phragmitis the rhu- 

 barb rust will be prevented. 



Anthracnose 



Caused by V ermicularia polygoni-virginica Schw. 



This disease is frequently found on old leaves 

 of rhubarb grown out of doors. It is of little eco- 

 nomic importance. 



Leaf Spot 



Caused by Ascochyta rhei E. and E. 



Like anthracnose, this trouble is of little impor- 



