Beet Diseases 



117 



liarity of this disease is that it seldom starts at the 

 top of the crown. The latter appears to be perfectly 

 healthy, although the leaves turn yellow, indicating 

 a diseased condition further down. Rotted roots are 

 found to be overrun by a varied flora, although 

 Pythium is the original cause of the trouble. For a 

 further description of the organism see p. 17. 



Control, The methods of controlling this dis- 

 ease are the same as those for lettuce drop, see p. 151. 



Downy Mildew 



Caused by Peronospora schachtii Fckl. 



This disease is of little economic importance in 

 the United States. The trouble, however, is preva- 

 lent in Europe. The mildew attacks the young seed- 

 lings in grayish patches on the under side of the 

 foliage. On older plants, the mycelium of the causa- 

 tive fungus works downwards into the root, causing 

 it to rot. 



Drop 



Caused by Sclerotinia lihertiana Fckl. 



Drop, which attacks young seedlings of the beet, 

 but not the older plants, is not very different from a 

 similar trouble on lettuce. The high temperature of 

 the soil soon after making the hot bed, is important 

 in favoring the disease. Sterilizing the soil with 

 formaldehyde, careful regulation of temperature, 

 and watering are methods to be observed in the con- 

 trol of the trouble. 



