May IS, 191S 



Seedling Diseases of Sugar Beets 



157 



isolate the causal organisms in 27 cases gave the following results: 

 Rhizoctonia, 15; Phoma, 8; Fusarium, 2; Mucor, i; undetermined, i. 

 Both of the parasitic forms were isolated from each of the two types of 

 soil developing disease. A good stand, which was thinned to three, 

 four, or, in a few cases, five plants per pot, was secured in each crock, 

 however, in spite of damping-off. Early in July evidences of crown-rot 

 developed in four of the six pots of unsterilized Colorado soil, but not in 

 that from Kansas. In two of these pots the stand was entirely destroyed 

 by July 21, and in a third there remained only one small seedling with 

 four leaves, which appeared after the original stand had been killed. 

 No disease appeared in the pots of sterilized soil, nor did root-rot develop 

 in the unsterilized Kansas soil. On July 23 inoculations were made with 

 a recently isolated Kansas strain of Rhizoctonia in two pots of each of the 

 six classes of soils. Two pots of each class were reserved as controls, and 

 two were inoculated with Phoma betae, as previously reported. The 

 inoculations were made on one beet only in each pot, by placing a piece 

 of beet-block culture on the crown and a second fragment against a 

 wound just below the surface of the soil. The other beets in the pots 

 were not disturbed in any way. One beet in each control pot was 

 wounded in a manner similar to that employed in the inoculations. 



The results in inoculated and in uninoculated pots are given in Table 

 V. It is worthy of note that as a result of inoculating i beet in each of 

 12 pots, 26 beets were killed and 7 more were so seriously diseased as to 

 be made worthless, while only 3 resisted infection. One beet attacked 

 in July by spontaneous rot recovered later. The fungus was recovered 

 in culture from several of the diseased roots. 



Table V. — Results of pot experiments with Rhizoctonia rot 



INOCULATED POTS 



Source of soil. 



Number 

 of beets 

 in pot on 

 July 21. 



Condition on October i8. 



Number 

 dead. 



Nunxber 

 infected 



but 

 living. 



Number 

 sound. 



Colorado 



Do 



Colorado (sterilized). . 



Do 



Kansas 



Do 



Kansas (sterilized) . . . 



Do 



Wisconsin 



Do: 



Wisconsin (sterilized) . 



Do 



Total. 



19 



4 



25 



28 



31 



34 

 13 

 16 



7 



3 

 a I 



4 

 4 

 3 

 4 



36 



26 



a The original stand of three beets had ab-eady been destroyed by spontaneous Rhizoctonia rot. 

 one plant living resulted from seed delayed in germination. 



The 



