July 14,1923 
Degeneration Diseases of Irish Potatoes 
55 
SPINDUNG-TUB^R DISEASE 
The spindling-tuber disease (43,44) is characterized always by spindli¬ 
ness and uprightness, and often by a darker green color and slight rugo¬ 
sity. The tubers are abnormally spindling, spindle shaped, cylindrical, 
and supplied with conspicuous eyes, these symptoms varying somewhat 
with the variety (PI. 7, A, 2, 3, B, 1, C, 1; 8, A, 2, B, 2, 3, C, 1, 2 ; 9, A, 
1, B, 1, 2; 10, B, 2, C, in center). A lighter red color obtains in spindling- 
tuber Red Bliss Triumph tubers than in the healthy tubers of this 
variety. This disease is readily distinguished from the mosaic diseases 
by the absence of mottling, and from leaf roll and streak. It is about 
as easily transmitted as mild mosaic and leaf-rolling mosaic, and there¬ 
fore less easily than rugose mosaic and streak, and more easily than leaf 
roll. It reduces the amount of tuber progeny, but because of the differ¬ 
ence in shape it may not be readily apparent that the size is reduced 
below that of uninfected plants. 
The spindling-tuber disease of the potato has been recognized for many 
years by growers and others by various names, such as “running out,” 
“running long,” “off shape,” “poor shape,” “reversion” and “senility.” 
Observations made by the writers on this potato trouble from 1917 
to 1921, in connection with investigations on mosaic and leaf roll, in¬ 
dicated its infectious nature. If strains free from this malady were 
planted near stock with a high percentage of “run out” tubers, a con¬ 
siderable percentage of such tubers resulted in a few years. Elimina¬ 
tion of “run out” tubers by selecting only the good, normal-shaped 
tubers at the time of planting did not produce stock free from such 
progeny. In fact, in some lots the percentage of spindling tubers in¬ 
creased during this period so that a few lots produced practically 100 
per cent spindling tubers. Similar selection of well-shaped tubers by 
growers from stock with a high percentage of spindling tubers, likewise 
has failed to produce stock free from this malady. A part of a strain 
planted under soil, temperature, moisture, fertilizer, and other environ¬ 
mental conditions similar to those of another part, with the exception 
that it was grown nearer spindling-tuber lots than the other, the next 
year contained a higher percentage of spindling-tubers. Furthermore, it 
was noted that normal and spindling-tuber progeny frequently developed 
in the same hill lot and even in the same tuber unit, just as obtains 
with mosaic and leaf roll. This was noted by Stewart ( 46 , PI. 10). 
Accordingly, during the season of 1921, additional selections for study¬ 
ing the nature of this malady were made. In a field of Green Mountains 
having less than 1 per cent of spindling-tuber, two lots of healthy hills 
were selected, one grown next and the other not next spindling-tuber 
hills; similar selections were made in two fields of Irish Cobbler having 
5 and 15 percent spindling-tuber hills, respectively. Further selections 
from Green Mountain and Bliss Triumph lots in experimental plots 
were made. In 1922, these different lots were planted and the percent¬ 
age of spindling tubers noted as indicated in Table III. 
Table III shows that the percentage of spindling-tuber decreases as 
the distance from diseased hills increases, and that a higher percentage 
of infection of healthy hills obtains as the percentage of spindling-tuber 
increases. These data also suggest that spindling-tuber may be trans¬ 
mitted fully as readily as mild mosaic in conditions apparently as favor¬ 
able regarding the source of infection. 
