206 



DISEASES OF ECONOMIC PLANTS 



is destructive upon the lima bean, producing upon pods 

 and leaves large, brown patches, mth the pyenidia ar- 

 ranged in concentric circles. When the disease is very 



prevalent, the pods fail to 

 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- r„j' „/„ o. \ T^l,' 



mose. After Halsted. ^^^^'^"^ SaCC). — ThlS, One 



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- 



