358 BULLETIN No. 189 [June, 



six strains ' ' Alternanthera B.A.F.," "Carnation K.F., " "Cauliflower," "Let- 

 tuce/' "Cotton," and "Dianthus barbatus. " Only one or two potato sprouts 

 came up from each hill and these were weak and spindling. After the tempera- 

 ture became too high in the greenhouse, the flats were placed outside, so that the 

 plants would develop further and produce tubers. The strains killed some of the 

 young sprouts and dwarfed the others, showing that they were able to attack the 

 potato plant. 



Here, as in the preceding experiments, the death rate of the vari- 

 ous plants was quite variable. These differences appear to be due to 

 the virulence of the fungus, to the susceptibility of the plant, or to a 

 combination of factors. 



EXPERIMENT 10 : INOCULATION OF VARIOUS HOSTS IN THE FIELD 

 WITH VARIOUS STRAINS OF RHIZOCTONIA 



All the inoculation experiments reported so far were conducted in 

 the greenhouse. In the summer of 1914 a fourth of an acre of land was 

 divided into three parts, separated by six-foot strips of ground. Sec- 

 tion 1 was inoculated on May 20 with twenty cubic feet of infected soil 

 taken from the inoculated benches in the greenhouse. The soil was 

 spread upon the section, worked under, and watered for several days. 

 Section 2 was left as a check. In Section 3 small bits of pure cultures 

 of various strains of Rhizoctonia were added with the seeds and plants. 

 The seeds were planted May 20, and the young plants were put in 

 June 16. Altho the drouth of the summer interfered considerably, 

 the results obtained were sufficient to show that RJiizoctonia Solani 

 was active under field conditions as well as in the greenhouse. 



No infection occurred in the first two sections. In Section 3 in- 

 fection was quite marked in a number of cases, especially on cotton, 

 potato, and several greenhouse plants. Where the strain ' ' Cotton I ' ' 

 was added to the cotton seeds, 100-percent infection occurred. In the 

 case of potato, to which ' ' Carnation R.F.2 ' ' was added, a marked dif- 

 ference was noticed, the plants in this section being dwarfed and 

 spindling, while in the first two sections they were bushy and strong. 

 The difference in the yield was as marked as the difference in growth 

 of the plants. All the coleus plants infected with "Coleus I" were 

 killed within two weeks after being set out. The same results were 

 obtained from inoculating salvia plants with the strain from salvia. 



DISCUSSION OF INOCULATION EXPERIMENTS 



In Table 11 are brought together, in tabular form, the results of 

 all the inoculation experiments, with the exception of No. 4, which 

 was carried on primarily to test the comparative virulence of isolated 

 and reisolated strains of Rhizoctonia. The thing that stands out at 

 first glance is the great variation in the mortality of the plants when 

 inoculated with strains from the same host and when inoculated with 

 strains from other sources. 



