VEGETABLE AND FIELD CROPS 209 



It consists of a rotting away of the lower portion of the 

 root, the crown and leaves remaining normal except in 

 the most severe cases, when the outer leaves may fall. The 

 rotted portion is honeycombed with cavities which are filled 

 with a viscous, colorless, sour-smelling fluid which exudes 

 on pressure. The decayed tissue is usually yellowish gray. 

 The rot seldom appears above the surface of the ground. 

 Young beets are not susceptible. 



The disease is favored by damp surroundings, as poorly 

 drained soil. In some cases large "damage is known to 

 result, sometimes fully 90 per cent of the crop being affected. 



It is inadvisable, if the disease is noted, to grow beets in 

 wet soil. 



Leaf spot (Pseudomonas sp.). — The leaves in this dis- 

 ease bear irregular, dark brown or black spots, 1 mm. to 

 3 cm. in diameter, chiefly upon the petiole, midrib, and 

 larger veins. Occasionally the discoloration extends along 

 a vein for some distance, and the tissue on either side 

 becomes brown and dry. 



The disease was first observed by Townsend in Utah 

 and Colorado, and its bacterial origin was demonstrated 

 by Nellie Brown. ^ 



Rust (Uromyces beta; (Pers.) Kiihn). — Rust has 

 long been known in Europe, where it was studied as 

 early as 1869. It is occasionally met in some of the 

 western states. Though not serious, it has been reported as 

 injuring the beet in market gardens in CaHfornia. It is 

 recognized by the characters of the true rusts, i.e. bUster- 

 like sori, consisting of pustules, of spores under the skin. 

 With the rupture of the skin the rusty pulverent mass of 



1 Brown, Nellie A., Sci. n. s. 29, 915, June 4, 1909. 

 P 



