DISEASES OF LEGUMINOUS PLANTS 71 



3. Remove and burn all plants at the close of 

 the season. 



V. Violet Root Rot of Lucerne i^Rhizoctonia 

 violacea) . — Fttngi Imperfecti, 



According to Kiihn, various other plants are 

 attacked, including potatoes, red clover, beet, 

 mangels, carrots, etc., but apparently cereals are 

 not susceptible. 



Symptoms, — Yellow patches appear in the crop 

 quite suddenly. Plants uprooted from such patches 

 v/ill be found to have the roots covered with a 

 brownish-violet ofrowth. In a bad case the stems 

 may also be attacked. 



Cause, — The facultative parasite Rhizoctonia 

 violacea is responsible for the yellow appearance of 

 the crop and violet covering of the roots. It 

 spreads its mycelium over the tap and side roots, 

 some of the threads penetrating the inner tissue, 

 thereby robbing the plant of nourishment, and 

 finally killing the roots and causing the falling of 

 the plants. 



So far no spore formation has been noticed, 

 but sclerotia may be found. The mycelium can 

 spread from plant to plant. The fungus doubtless 

 belongs to the Basidiomycetes. 



Preventive Measitres. — 



1. The fungus grows best on sour soil, therefore 

 sweetening the land by liming checks its growth. 



2, For the same reason drain land well. 



