A DRYROT CANKER OF SUGAR BEETS 



By B. L. Richards 

 Department of Plant Pathology, Utah Agricultural Experiment Station 



What appears to be an undescribed rootrot of the sugar beet was first 

 called to my attention on August 5, 1920, by Mr. A. H. Bateman. Speci- 

 mens of the diseased beets collected at this date at Cornish, Utah, ex- 

 hibited numerous brown, circular lesions that varied from j^ inch to i 

 inch in diameter (PI. 4 ; 8, D ; 9, A, B) . The outer surface of the root cov- 

 ering these lesions, which in most cases remained entire, had so sunken as 

 to give a definite undulating contour of alternating light and dark brown 

 concentric areas or rings (Pi. 4). The removal of this outer layer of cells 

 of the older lesions exposed deep cankers or pockets filled with hyaline- 

 mycelium embedded in the dry remains of partially decayed host cells. 

 This accompanying mycelium, when exposed to the atmosphere through 

 the cracking open of the outer covering, appeared dark brown in color 

 and immediately suggested the typical mycelium of the sterile, or 

 "Rhizoctonia," stage of Corticium vagum B. and C. The general prev- 

 alence of black sclerotial bodies on the outside of the diseased beets 

 (PL 7, A), together with the microscopic examinations made at this time, 

 confirmed this initial suggestion. 



An examination of the field from which these first diseased specimens 

 were taken revealed the trouble to be of considerable economic impor- 

 tance; at least 20 per cent of the beets in this field of 40 acres were 

 diseased. The disease appeared to be confined to definite areas wherein 

 every beet might be found infected. These diseased spots varied con- 

 siderably in size and appeared to be widening most rapidly in the direc- 

 tion parallel with rows. Three adjacent fields were found at this time 

 to be seriously diseased, but none to the same degree as the field first 

 visited. 



The progress of the disease in these fields appeared of such ominous 

 character as to require immediate investigation. However, as the 

 season was well advanced, little more than preliminary experiments 

 were undertaken. The results to date, while definite, are not sufiiciently 

 extensive to warrant final conclusions, and many of the important rela- 

 tions of the disease remain obscm-e; nevertheless it is felt that the 

 apparent economic importance of the trouble justifies a preliminary 

 description at this time. 



The disease is first detected in the field by abnormal wilting of the 

 leaves in the daytime with partial or complete recovery at night. Later 



Journal of Agricultural Research, Vol. XXII, No. i 



Washington, D. C. Oct. i, 1921 



zm Key No. Utah-14 



54817°— 21 4 (47) 



