206 



DISEASES OF ECONOMIC PLANTS 



is destructive upon the lima bean, producing upon pods 

 and leaves large, brown patches, with the pycnidia ar- 

 ranged in concentric circles. When the disease is very 



prevalent, the pods fail to 



V 



mature their seeds. 



Spraying with Bordeaux 

 mixture is recommended. 



Powdery mildew {Ery- 

 siphe polygoni DC). — The 

 characters of the powdery 

 mildews as described for 

 the grape apply here suffi- 

 ciently to serve for recog- 

 nition purposes. This dis- 

 ease is not usually serious, 

 and is amenable to treat- 

 ment with flowers of sul- 

 phur or spraying with liver 

 of sulphur. 



BEET 



Leaf spot (Cercospora 



Fig. 93. - Lima bean pods showing Pho- ^^^ -^^^^ ^^^^y _ ^j^- 

 mose. After Halsted. ^ ' 



of the several leaf spots 

 upon the beet, is very widespread in the eastern and middle 

 states. Very few fields are entirely free from it. It occurs 

 upon all varieties, but is especially injurious to the sugar 

 beet. 



The round, brownish, purple-bordered spots turn ashen 

 in the center, and when mature, often become so thin and 

 brittle as to drop out, leaving ragged holes. The sporif- 



