136 Journal of Agricultural Research voi. iv, no. 2 



serious losses. Many of the failures attributed to faulty germination are, 

 in fact, the results of serious outbreaks of this disease, and in practically 

 all the cases investigated where seedlings were "not growing well" the 

 trouble has been found to be root sickness. 



These or similar diseases have been known for a long time in Europe, 

 where various and widely different theories have been advanced regarding 

 their cause or causes. Refractory soil, cold ground, wet weather, poor 

 cultivation, excessive rain, fungus infection, and the like have all had 

 their advocates, who have based their opinions in many instances upon 

 insufficient data. 



Hesse (24) ^ reported the presence of Pythium deharyanum in diseased 

 beet seedlings in 1874, but he seems to have done no experimental work 

 with this host. Hellriegel (23), one of the first investigators who made 

 a careful experimental study of this subject, showed that damping-ofif 

 in his pot experiments appeared to be due to a parasite, and traced the 

 source of infection to the seed. He did not, however, assign a specific 

 organism as the cause. Eidam (13) produced artificial infection of beet 

 seedlings with cultures of Rhizocionia hetae Kiihn. Kriiger (25, 26) 

 found Phonia hetae Fr. to be an active seedling parasite of the sugar beet 

 and expressed the opinion that several different fungi are capable of pro- 

 ducing diseases in seedlings of this plant so similar in appearance that 

 they have been classed together under the name "Wurzelbrand." Sev- 

 eral fungi, as well as bacteria, have since been added to this list of para- 

 sites, while other writers have denied the parasitic origin of the disease. 



So much contradiction and uncertainty exists in the literature of the 

 last 20 years regarding the nature and cause of Wurzelbrand of beets 

 in Europe that Peters (31, 32, 33) and his associates (5, 6) found it neces- 

 sary to go over the entire subject and submit to rigid experimental proofs 

 the more worthy of the hypotheses that have been put forth. • 



From what appears to be a careful and trustworthy piece of work, 

 Peters (33) concludes that under the conditions of his experiments 

 Pythium deharyanum Hesse, Phoma hetae Fr., and Aphanomyces laevis 

 De By. are capable of producing damping-off of the sugar beet. He was 

 unable to secure pure cultures of Rhizocionia violacea Tul., but he infected 

 soil with fragments of beets showing typical Rhizoctonia decay and 

 failed to produce damping-off. The evidence of the parasitism of bac- 

 teria on this host seemed to him insufficient to justify serious consideration. 



In America the only reported work on seedling diseases of beets, 

 except the author's preliminary note (12), is by Duggar (9, 11), who 

 conducted successful infection experiments with a species of Rhizoc- 

 tonia that he secured from decayed beets and later designated as Cor- 

 ticium vagum B. and C, var. solani Burt. (10, p. 444-452). His experi- 

 ments were carried out in sterilized soil and controlled by check plants 



' Reference is made by number to " Literature cited," p. 165-168. 



