124 Diseases of Truck Crops 



Drop 

 Caused by Sclerotinia libertiana FcH. 



Drop on beets, which attacks young seedlings, but 

 not older plants, is otherwise not very diflEerent from 

 a similar trouble on lettuce. Clinton' reports a case 

 of beet drop in an outdoor seed bed. The warm con- 

 dition of the soil, soon after making the seed bed, 

 was important in favoring the disease. Sterilizing 

 the soil with formaldehyde, careful regulation of 

 soil temperature and watering are methods to be 

 observed in the control of the trouble. 



Rust 



Caused by Uromyces betce Kuhn. 



This disease has been reported only on beets in 

 Califomia. In Europe it is especially common on 

 the wild beet {Beta maritima). 



The Organism. The cause of this rust is a fungus, 

 Uromyces beta, the latter having three spore stages, 

 all of which occur on the same host, but at different 

 times of the year. 



I. Spring or Cluster Cup Stage. This is seen as 

 small, whitish, raised cups, grouped on a yellow spot^ 

 When opened, these cups emit a yellowish powder 

 which is made up of large quantities of the yel- 

 low colored aecediospores. The latter germinate 



' Clinton, G. P., Report of the Botanist for 1915, Connecticut 

 Agr. Expt. Sta. 39th Ann. Rept. : 433-4..16. iqis. 



