Mayi5. I9I5 Seedling Diseases of Sugar Beets 165 



made to isolate pathogenic organisms, but with negative results. Several 

 of the plants upon which decay already had made considerable progress 

 were placed in fresh soil in the greenhouse and held under observation to 

 determine whether the disease would continue to develop. Without ex- 

 ception these plants healed and thereafter showed no evidences of disease. 

 The foliage which they put forth was normal, giving no evidence of the 

 brittleness or blue-green color noted in the field. The results seemed to 

 justify the conclusion that the plants were suffering from excessive alkali 

 brought in by seepage from the neighboring reservoir. 



SUMMARY 



The more important points brought out in this paper may be sum- 

 marized as follows : Four fungi have been found to stand in a causal rela- 

 tion to damping-off of sugar beets in America. These are Phoma betae 

 (Oud.) Fr. ; Rhizoctonia sp. probably identical with Corticium vagum B. and 

 C, var. solani Burt.; Pythium debaryanum Hesse; and an undescribed 

 member of the Saprolegneaceae. 



Under favorable conditions of culture, plants attacked by Phoma betae 

 or Rhizoctonia may recover either temporarily or permanently. Attacks 

 of the other two fungi upon the seedlings may be expected to prove fatal. 

 Phoma and Rhizoctonia are capable of producing characteristic decay in 

 mature beets. The former appears to infect the plants primarily in the 

 seedling stage, and when recovery occurs it remains thereafter in a dor- 

 mant condition upon the host. It occasionally develops a characteristic 

 black rot on growing beets in the field and more frequently appears upon 

 mother beets in storage. When it does not destroy the root, it may infect 

 the seed stalk and appear upon the mature seed. Control measures are 

 to be sought in proper cultural methods and seed treatment which looks 

 forward to the production of seed free from infection. Pythium debary- 

 anum is capable of attacking the feeding roots of the beet throughout its 

 vegetative period, and the new fungus is also able to cause trouble on 

 mature beets in a similar manner. Rhizopus nigricans Ehr., while unable 

 to produce disease on normal plants in the field, is capable of attacking 

 the tissue of dead or dormant sugar beets, producing a characteristic 



decay. 



LITERATURE CITED 

 (i) Atkinson, G. F. 



1892. Some diseases of cotton. Ala. Agr. Exp. Sta. Bui. 41, 65 p., 25 fig. 



(2) Balls, W. L. 



1906. Physiology of a simple parasite. Preliminary note. In Yearbook, 



Khediv. Agr. Soc., 1905, p. 173-195, pi- 6-7. 



(3) 



1907. Physiology of a simple parasite. Pt. 2. In Yearbook, Khediv. Agr. 



Soc, 1906, p. 93-99, pi. 13-16. 



(4) Barrett, J. T. 



1912. A serious root disease of radish. (Abstract.) In Phytopathology, v. 2, 

 no. 2, p. 96. 



