FUNGI AFFECTING ALFALFA 



The Alfalfa Leaf=blight 



Cercospora helvoki var. mecUcaginis 



This disease has been studied by Professor F. D. 

 Chester, of Delaware, who reports that it •* shows itself 

 upon the leaf as siib-eirciihir, or elliptical spots of a 

 smoky brown, or almost black color, equally Ausible upoii 

 both sides, and vary- 

 ing fro ni one -six- 

 teenth to one-thirty- 

 second of an inch in 

 diameter. The spots 

 are without well-de- 

 fined borders, which^ 

 when closely exam- 

 ined, are somevrhat 

 irregular, shading in- 

 distinctly into the. 

 surrounding leaf tis- 

 sue. Spots coales- 

 cing cause the leaf to 

 turn yellow and brown, completely destroying it.'' 

 The same fungus is believed, occasionally, to attack 

 the red clover and scarlet clover, although it is seldom, 

 if ever, seriously destructive to- these crops. The myce- 

 lium threads of the fungus push about between the cells 

 of the leaf, absorbing their contents^ and causing the 

 discoloration of the foliage, ^hen ready to fruit, the 

 threads develop abundantlv at certain points just beneath 



FIG. 88. 



a. Spore: 



ALFALFA BLIGHT Fr>'GUS. 



I. secTiou of leaf. Mag-nified. 



