48 Journal of Agricultural Research voi. xxii. no. i 



the older leaves fail to recover, turn brown, and die. This dying of the 

 outer or older leaves continues with the progress of the disease in the 

 root until all the leaves on the affected beets may succumb. Localized 

 browning frequently occurs in the blade and petiole, but to date no 

 suggestion of a parasitic relation has been found. Neither the petiole 

 decay reported by Duggar (2) ^ nor the "western crownrot" described by 

 Edson (j) have been found associated with thedryrot canker in the field. 

 A peculiar type of crownrot, however, is found late in the season, usually 

 well toward harvest time (PI. 6; 8, B). A study of a number of these 

 crownrot specimens indicates definitely that the causal organism enters 

 the beet below the stu-face of the soil and works upward in the tissues, 

 eventually destroying the crown. The fungus has not been observed 

 to attack the beet above the soil line. 



It is evident that the fungus is unable to destroy the outer corky cells 

 of the beet root, but gains entrance to the inner tissue at a definite 

 point and works tangentially just beneath this outer layer. As the 

 fungus eats its way from the point of entrance the outer tissues, due to 

 killing and subsequent drying out of the cells beneath, sink in such a 

 manner as to produce the circular lesion with its very definite undulating 

 contour of alternating raised and sunken concentric "rings" (PI. 4). 

 The lesions appear first as a small, brown, sunken spot with a minute 

 perforation in the center (PI. 8, D). The first definite concentric "ring" 

 which is considerably sunken below the central area and usually dark 

 brown in color is noted before the lesion reaches a diameter of >^ inch. 

 With continued enlargement a second and somewhat broader "ring," 

 less sunken and much lighter in color, results. Similar concentric areas 

 are developed alternately until the fimgus reaches its limit of lateral 

 spread. Individual lesions resulting from a single point of infection 

 may obtain a size of from ^ to i inch in diameter and develop as many 

 as eight alternate "rings" (PI. 4). When, however, adjacent lesions 

 become confluent, as they frequently do (PI. 4; 8, D; larger 

 lesions result which may in severe cases cover a large part of the root 

 surface. In such cases large concentric rings are produced, which become 

 common to a number of centers of original infection (PI. 4; 8, D; 9, A, B). 



Another characteristic feature of the disease results in cases where 

 infection occurs at or near the apex of the root. The root in such an 

 event is usually severed at the point of infection and the fungus advances 

 upward, producing the typical dryrot with resultant concentric rings 

 which may encircle the entire root (PI. 7, B). Again, cankers may occur 

 with such frequency as to girdle completely the root (PI. 8, A). 



The distinctive feature of the contour, as shown in Plates 4 and 8, D, 

 is obtained usually before the fungus penetrates deeply into the tissue 

 of the beet and before a serious rupture of the outer layer occurs. With 



1 Reference is made by number (italic) to "I,iterature cited," p. 52. 



