Alfalfa in Kansas. 



341 



ALFALFA LEAF-SPOT DISEASES. 



These are caused by specific fungi which penetrate the tissues of the 

 leaves and kill definite areas. On account of their invasion the vital 

 functions of the leaves are interfered with, and as a result they die; 

 this, in turn, reduces the vigor of the entire alfalfa plant. Not only do 

 the leaves die, but they dry up and drop off from the stems more readily 

 than under normal conditions. In fact, a great share of the hay crop is 

 oftentimes sacrificed on account of this loss of foliage. 



Fia. 284. Alfalfa leaf spot (Psetido- 

 peziza medicaginis Lib. Sacc.), show- 

 ing characteristic spotted condition of 

 the foliage. The leaves have dropped 

 from the alfalfa stem as a result of 

 this disease. 



FIG. 285. Alfalfa leaf spot (Pseudo- 

 peziza medicaginis Lib. Sacc.). The 

 spots are circular in outline and only 

 about one-sixteenth of an inch in di- 

 ameter. 



ALFALFA LEAF SPOT (Pseudopeziza medicaginis [Lib.] Sacc.). This 

 disease is recognized by its small, sooty-brown or blackish spots, which 

 are most characteristic on the upper surfaces of the leaves. (See Fig. 

 284.) The spots are circular in outline and only about one-sixteenth of 

 an inch in diameter. (See Fig. 285.) They occur so abundantly, how- 

 ever, that they injure the foliage sufficiently to cause it to drop. It is 

 very frequently called a "rust" or "blight." It may attack plants which 

 are growing even under the best of soil conditions, and is very often 

 more severe during a dry season than during a wet one. It may prac- 

 tically ruin or destroy a young field, and older fields are likewise very 



