May IS. 191S Seedling Diseases of Sugar Beets 1 39 



methods of inoculation were employed, but the results were uniformly the 

 same. Either suspensions of spores or mycelial growth on various cul- 

 ture media, such as agar, com meal, beet petioles, and steriHzed beet 

 blocks, were employed. The last method — that is, with beet blocks — 

 was perhaps the most satisfactory and convenient. The corn-meal 

 cultures appeared to exercise an unfavorable physiological action, pos- 

 sibly because of the bacterial growth which they fostered; so this 

 method was discarded. 



Inoculation experiments were invariably controlled by a considerable 

 number of uninoculated pots. In a few instances disease occurred in 

 the controls. In such cases the causal organism was determined, but 

 the entire series was abandoned as an inoculation experiment, even 

 though the presence of an intruder could be explained readily through 

 the agency of insects and earthworms. It was the invariable custom to 

 recover the fungus from the damping-off seedlings by the method already 

 described (PI. XVI and XVII) and to reinoculate and recover through 

 from four to six generations of seedlings. 



As reported in a former note (12), four fungi have been found to stand 

 in causal relation to seedling-beet troubles. These are Photna betae (Oud.) 

 Fr., a species of Rhizoctonia, regarded as identical with the form 

 described as Corticium vagum B. and C, var. solani Burt., Pythium 

 debar yanum Hesse, and a fungus originally reported as Aphanomyces 

 laevis De By., but which has since been found to be new. 



PHOMA BETAE 



TAXONOMY 



Frank (16, 17, 18, 20) established the relation of Phoma betae to 

 heart-rot of the sugar beet in 1892. The following year Kriiger (25, 26), 

 working in the same field, demonstrated its causal relation to damping- 

 off. He found the fungus fruiting abundantly on all parts of diseased 

 beets and held it to be identical with the fungus which had previously 

 been observed on various portions of the cultivated varieties of Beta 

 ■vulgaris L. 



Oudemans (29, p. 181) had observed what appeared to be the same 

 fungus fruiting upon leaf spots of old beets and applied the name "Phyl- 

 losticta betae." Prillieux (35, p. 19) observed the fungus on leaf blades 

 and decaying heart leaves, as well as upon typical spots on the leafi 

 and applied the name " Phyllosticta tabifica." Saccardo recognizes the 

 names "Phyllosticta betae Oud." and "Phoma betae Rostr." The latter 

 name is given on the authority of the following paragraph from the pen 

 of E. Rostrup (41, p. 323): 



Eine zweite, an Runkelriiben anftretende Phoma habe ich zucrst in mcincm 

 Jahresbericht iiber Krankheiten der Kulturgewachse ira Jahre 1888 (Tidsskrift for 

 Landokonomi. R. 5, Bd. 8, S. 746) [40] unter dem Namen Photna sphaerosperma 

 beschrieben. Weil sich aber herausstellte, dass dieser Name schon im Jahre 1885 

 einer ganz anderen Art gegeben war, nannte ich spater den Pilz Phoma Betae. 



