164 Diseases of Economic Plants 



the surface of the beet than in the case of the potato, and 

 tends more to form corky growths upon the surface than 

 to make deep cavities. Beets shoukl not be grown upon 

 land known to be infested with the potato scab or to have 

 borne a badly infected crop of beets. See also potato scab. 



Bacterial Leaf-spot ^''" {Pseudomonas aptatum (B. & J.). 

 — The leaves in this disease bear irregular, dark brown 

 or black spots, 1 mm.-3 cm. in diameter, chiefly upon the 

 petiole, midril), and larger veins. Occasionally the dis- 

 coloration extends along a vein for some distance, and the 

 tissue on either side becomes l)rown and dry. 



The disease was first observed by Townsend in Utah and 

 Colorado, and its bacterial origin was demonstrated by 

 Brown. 



Rust {Uromyces hetce (Pers.) Kuhn) has long been known in 

 Europe, where it was studied as early as 1869. It is occa- 

 sionally met in some of the western states and has been 

 reported as injuring the beet in market gardens in California. 

 It is recognized by the characters of the true rusts, i. e., 

 blisterlike sori. 



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. 



White-rust (Albugo hliti (Biv.) Ktz.). — The sori are 

 blisterlike, as in the true rusts. The rupture of the epidermis 

 releases masses of snow-white spores. 



Soft-rot ^^^ {Bacterium teutlium Met.) was prevalent in 

 Nebraska in 1904. Leaf-scorch.'-'^- — The leaves blacken 

 and die, and the roots are small, discolored, and poor in 

 sugar content. Crown-gall and Root-tumor (Urophlyctis) , 

 Downy-mildew (Peronospora) , and Drop (Sclerotinia) cause 

 some loss. 



BROCCOLI. See cabbage. 



BRUSSELS SPROUTS. See cabbage. 



