May IS, 191S 



Seedling Diseases of Sugar Beets 



143 



VITALITY IN CULTURE 



Phoma hetae exhibits long vitality in culture, as is shown by the follow- 

 ing tests. 



On July 2, 1 91 3, old cultures which had been apparently air-dry for 

 months were opened under sterile conditions, and into each a portion of 

 string-bean agar was introduced. The tubes were then placed to harden 

 in such a position as to leave the old culture partly submerged. Table 

 III gives the age of the cultures and the results after six days' incubation. 



Table III. — Vitality of Phoma betae in culture 



INOCULATION EXPERIMENTS ON SEEDLINGS 



The strains used in inoculation experiments are 24 in number, obtained 

 from the following sources : 



Direct isolation from sugar-beet seed by the moist-chamber method, i. 



Indirect isolation from sugar-beet seed through damping-ofif seedlings 

 in sterilized soil, 2. 



Direct isolation from Phyllosticta leaf -spot, 2. 



Isolations from various sources such as beet leaves, beet seed, and 

 beet-sick soil at Rocky Ford, Colo., 13.^ 



Isolations from beets having heart-rot, from Colorado, i ; Wisconsin, 

 2; South Dakota, i. 



Isolations from seedlings grown in sterilized soil, inoculated with 

 decayed beets, 2. 



The inoculation experiments upon seedlings were carried out in the 

 maimer already described, invariably yielding positive results. There 

 appeared to be no decrease in virulence from carrying the fungus in 

 culture 14 months. 



The first development of damping-off in the pots occurred usually 

 about the third day after the seedlings broke the ground and continued 

 till about the time they developed their third or fourth pair of leaves 

 (PI. XVIII, fig. 2). The method followed was to sow 100 seed balls per 



1 These cultures were kindly supplied by Miss Venus W. Pool, of the Bureau of Plant Industry, from 

 the Rocky Ford (Colo.) field station. 



90271°— 15 4 



