156 Journal of Agricultural Research voi. iv. no. 2 



less rapid. The fungus was readily recovered in culture from them. 

 A photograph of the most seriously injured beet taken at the time of 

 harvest on October 23 is reproduced in Plate XXII, figure 2. At that 

 time the scars where the original infection had been produced could be 

 found on all the beets. Some showed small areas of decay, but most 

 of them were practically sound. 



A third series of inoculations were made on September 1 1 through knife 

 wounds near the surface of the ground. These were made in imitation of 

 cultivator injury and were infected by placing a rapidly growing culture 

 of Rhizoctonia sp. on a beet block directly in contact with the injured 

 surface. Thirty beets were inoculated; none of them was destroyed. 

 About half of the number healed completely, so as to leave only a local 

 scar at the point of inoculation. The others showed local decay, more 

 or less characteristic of crown-rot. The fungus was readily recovered 

 from several of these. The largest decayed area produced was about 

 4 inches in diameter. At least half of this beet was still sound. 



At the time of harvest the beets which showed no decay were topped 

 to remove the leaves, the crown being left uninjured. They were placed 

 on racks in the vegetable cellar and examined for decay from time to time. 

 On April 3 all but two of them showed evidence of rot, although in most 

 cases a close examination was necessary to discover it. Eighteen were 

 selected and submitted to cultural tests for Rhizoctonia. Out of 68 

 attempts to isolate the organism 54 yielded Phoma hetae, 2 failed 

 to develop, and the remaining 12 gave growths of various saprophytes. 

 In no instance was it possible to secure a culture of Rhizoctonia. It was 

 apparent that those beets which failed to develop decay in the fields had 

 entirely thrown off the infection from Rhizoctonia. 



In order to determine to what extent this resistance to attack is to be 

 attributed to local conditions of climate or soil, two large lots of soil from 

 seriously infected beet fields, one in Kansas and one in Colorado, were 

 shipped to Madison, Wis. Both types of soil were quite heavily infected 

 with Rhizoctonia sp. That from Kansas was a sandy loam deficient in 

 organic matter. It had received generous applications of factory waste 

 lime and was of good mechanical texture. The Colorado soil was of 

 compact structure containing an admixture of clay and fine silt. It was 

 very deficient in organic matter, so that it was quite impervious and 

 lumped badly. These soils were placed in unperforated, unglazed, 

 12-inch crocks containing cinders at the bottom for drainage, and sunk 

 into the ground out of doors to within 2 inches of the top. Soil from 

 Madison was employed in similar crocks as a control. Six crocks of 

 each soil were sterilized in an autoclave by heating for 12 consecutive 

 hours under 15 pounds' pressure, and six were left untreated. Untreated 

 beet seed which showed remarkably strong germination and less than 

 I per cent of infection with Phoma hetae was sown. Damping-off developed 

 only in the unsterilized soil from Kansas and Colorado. Attempts to 



