Nov. i, 1915 
Potato Tuber-Rots Caused by Fusarium Spp . 
197 
F. radieicola 2890 plus Rhizoctonia sp. 2892. The two organisms were 
used in combination, 14 tubers being inoculated and incubated as above. 
More advanced decomposition seemed to take place than when F . radi- 
cicola alone was present. However, the species of Rhizoctonia could 
not be recovered, but F. radieicola was reisolated wherever the attempt 
was made. 
F . radieicola 3021; reisolation of 2890-from a Burbank potato 20 days 
after inoculation with the latter. With this reisolated strain an attempt 
was made to ascertain the effect of the temperature factor on the action 
of the organism. The inoculated tubers (Irish Cobbler variety) were 
badly decomposed at average temperatures of 23.3 0 , 20.2 0 , and 19.5 0 C. 
At 18.7° the majority were more seriously affected than at lower tem¬ 
peratures; indeed, at 17.5 0 and 15.i° the effect was a slow dry-rot, while 
at 12.5 0 the organism persisted for 88 days without perceptible damage 
to the host. 
F. radieicola 3023. Another reisolation of strain 2890; from lenticel 
infection after 20 days' incubation at 23 0 C. All tubers of the three 
varieties Netted Gem, Idaho Rural, and People's inoculated with this 
strain and incubated for 21 days at an average temperature of 25.6° were 
very badly decomposed. The organism was recovered by three isolations. 
F. radieicola 2998; isolated March, 1914, from a stem-end ring disease 
and wound-infected tuber from Fallon, Nev. Culture used, 12-day-old 
pionnotes on stem of MelUotus alba . All tubers inoculated with this strain 
and incubated 20 days at 23 0 C. rotted. The organism was recovered. 
F. radieicola 3236; isolated in August, 1914, in association with F. hyper - 
oxysporum from a soft-rotting tuber from Ocean Springs, Miss. Culture 
used, 1-month-old potato cylinder. The results with this strain are 
as follows: One tuber incubated for 14 days at 25.7 0 was badly softened 
with wet-rot: The organism was recovered. Nine tubers at 24.6° for 
24 days were slightly rotted in every inoculation prick, one tuber being 
completely softened with grayish wet-rot. Organism recovered by two 
reisolations. Sixteen tubers incubated 51 days at temperatures ranging 
from 16.3 to 18.4° C. gave the following results: At lowest temperature 
no rot occurred, but the organism had become established; two of the 
four tubers at 17 0 were rotting slightly, with the organism established 
in the others; at 17.8°, two were slightly rotted, with the organism 
persisting in the others; at 18.4° one tuber was sound and the three 
others were rotting. 
F. radieicola 2862; isolated October, 1913, from jelly-end rot of a tuber 
of the Burbank variety from Sargent Island near Middle River, Cal. 
Culture used, 9-day-old pionnotes on stem of MelUotus alba . This strain 
was comparatively inactive, only 12 per cent of the inoculated tubers 
rotting after 20 days' incubation at 23 0 C. The organism was recovered. 
9838°—15—2 
