FORAGE CROPS 383 



Downy mildew (Peronospora Trifoliorum DeBy.). — 

 Downy mildew, which is a serious pest in Europe, has 

 been reported in America from Colorado, Kansas, New 

 York, and North Carolina, though it has not yet been de- 

 structive in this country. The affected parts of the leaf 

 turn yellowish gray to purple, and are frequently curled. 

 The leaves, as seen from below, are coated with the downy 

 fuzz, violet when old, characteristic of this class of diseases. 



Rust {Uromyces striatus Schroet.). — The true rust of 

 alfalfa may be recognized by the typical rust sori, which 

 are, in this case, chiefly upon the lower sides of the 

 leaves. It is not usually serious. 



Gloeosporiose (Gloeosporium Medicaginis Ell. & Kell.). — 

 Black, rather prominent acervuli appear chiefly upon the 

 lower surfaces of leaf spots. The lower leaves often turn 

 yellow and die. 



Seed mold {Alternaria sp.). — Brown, dead, shriveled 

 seeds are often noted in samples of alfalfa seed. Such 

 seeds, if planted, develop, apparently from within, a dense 

 black mold due to a species of alternaria. 



The economic importance of this condition is not known. 



Damping off (Rhizoctonia sp. and Pythium DeBaryanum 

 Hesse). — The damping off of alfalfa is chiefly caused 

 by the two fungi above named. Damping off is discussed 

 in general on p. 60. 



It has been known to affect alfalfa seedlings in the green- 

 house, and it may occur to some extent in the field, especially 

 the form caused by rhizoctonia. 



Stagonosporose {Stagonospora carpathica Baeuml.). — 

 This in no case destructive leaf spot has been noted only 

 in New York, and is described as follows by Stewart, 



