210 DISEASES OF ECONOMIC PLANTS 



spores is uncovered. As in the case of the asparagus rust 

 there are three stages, — spring, summer, and winter. 



Removal of the leaves bearing the spring stage and spray- 

 ing with Bordeaux mixture has been recommended. Af- 

 fected leaves used as feed may carry the disease through 

 the manure to plants of the following season. 



Root rot, phomose {Phoma betae Rostr.). — Upon the roots 

 a shrunken, coal-black discoloration, extending sometimes 

 quite to the center, indicates the presence of this dry rot. 

 No disagreeable odor attends the rot. Upon the affected 

 surface pycnidia appear as very minute pustules. Upon 

 the leaves this same fungus forms large circular dead spots. 



All infected leaves should be removed from the roots 

 before placing in storage. 



White rust {Albugo bliti (Biv.) Ktz.). — The white rusts 

 are in some aspects similar to the true rusts, but they are 

 always white, never rusty or black in color. The sori are 

 bhster-like, as in the true rusts. The rupture of the 

 epidermis releases masses of snow-white spores. 



This disease is seldom of serious import, and no -preven- 

 tive measures have been recommended. Should it become 

 troublesome, clean culture will be necessary. The same 

 disease occurs upon the pigweeds (Amaranthus), which are 

 botanically close kin to the beet. 



Damping ofif . — Damping off of seedlings near the surface 

 of the ground soon after they come up, often before thin- 

 ning, is a frequent cause of loss. The leaves yellow, 

 the roots turn brown, and the plants topple over and die. 

 This is in some instances due to the usual causes of damp- 

 ing off, p. 60; sometimes to a heavy crust formed upon the 

 soil, thus preventing the safe emergence of the seedhng. 



