A Dry Rot of the Irish Potato Tuber 
49 
rarely in either terminal or intercalary position. Size 6-12 x 8-12 
mu. 
Occurrence : On tubers of Solatium tuberosum, causing a dry 
rot, and upon dry potato stems. 
ETIOLOGY. 
TUBER INFECTIONS. 
A very large number of inoculation experiments have now 
been made so that the connection of Fusarium tuberivorum with 
this Nebraska tuber rot is fully established. 
The first inoculations were made in 1908 on tubers grown in 
eastern Nebraska. Puncture inoculations into these tubers gave 
no evidence of rotting, due no doubt to the comparatively great 
resistance of these tubers to invasion by this fungus. 
Table 9. — Inoculations of western Nebraska tubers made during 
the winter of 1908-1909. 
No. of 
tubers 
No. of inocu- 
lations per 
tuber 
Method of 
inoculating 
Humidity 
No. of successful 
inoculations 
12 
4 
Puncture .... 
60 
48 
10 
4 
Puncture ... 
Over H 2 S0 4 
40 
8 
4 
Puncture . 
Saturated air . . . 
16 
3 
4 
Smear 
60 
Tubers showed a 
soft bacterial 
Check 
rot. 
2 
4 
Puncture with 
sterile needle 
60 
None 
The tubers kept in a desiccator over sulfuric acid and those 
kept at the humidity of the laboratory (averaging about 60 per 
cent during the experiment) gave the largest number of success- 
ful inoculations and the greatest amount of rotting. These pre- 
liminary experiments clearly established the causal relation of 
this specific fungus to the dry rot of these tubers. 
Extensive inoculation experiments were conducted during the 
spring of 1910 with several bushels of large healthy Early Ohio 
and White Ohio tubers grown in Box Butte County. The follow- 
ing types of inoculation were employed in this work : 
1. Contact with infected tubers. 
2. Punctures. 
A. At the "eye." 
B. At some other point on the surface of the tuber. 
3. By removal of the "skin" of the tuber. 
4. Surface infection, with and without media. 
A. At the stem end of the tuber. 
B. At a lenticel. 
