42 
Journal of Agricultural Research 
Vd. XXIII, No. I 
Farm, Va., with two varieties of potatoes, Irish Cobblers and Bliss 
Triumphs, and two strains of the fungus. One of these latter, culture 
No. 126, 3 was isolated in July, 1918, from a decaying potato tuber grown 
in North Carolina and the other, culture No. 127, in May, 1918, from a 
diseased potato stem grown in Arkansas. The diseased material from 
both sources represented clear cases of the Sclerotium infection. 
Ten tubers of each variety were inoculated in 1919 with Sclerotium 
No. 126 and 10 with Sclerotium No. 127, making a total of 40 inoculated 
tubers. In addition, a number of uninoculated tubers of both varieties 
were planted for control. All these potatoes were grown the preceding 
season in Aroostook County, Me., where sclerotium-rot has never been 
found. The inoculations were made a few days before planting, a 
sclerotium or two being inserted in a narrow channel made in each tuber 
by means either of a cork borer or a needle. When the potatoes were 
taken to the field a few millimeters of decay could be noted in every 
tuber on cutting. The planting was done on May 19, following a period 
of rainy weather. There was an abundance of moisture in the soil, 
although the surface of the ground was reasonably flat. The two months 
following the planting were characterized by prolonged warm and dry 
weather, intermittent with two rainy periods. 
The effect of Sclerotium rolfsii on growing potatoes in this test was 
extremely disastrous. Part of the plantings did not show above the ground 
at all, part perished from damping-off, and most of the remainder grad¬ 
ually wilted and died before maturity. The progress of the disease 
during the season was as follows: 
June 10. Number of missing hills. . 11 
June 10. Number of small plants (1 to 3 inches) damped-off. 7 
June 18. Number of larger plants showing wilt. 10 
June 24. Additional number of wilting plants. 6 
July 14. Additional number of wilted plants. <. 1 
Total number of missing and wilted plants. 35 
The remaining five plants, although considerably weakened, remained 
alive until harvest. Their size was only about half that of the plants in 
the control row, but the foilage and the stems were practically normal 
in appearance (PI. 1, B). It is probable that the action of the parasite 
in these cases was confined to the root system alone. 
At digging time, on September 15, no tubers were found in any of the 
35 hills wilted or otherwise destroyed by the fungus. The other 5 hills 
produced a few tubers of the size of a hazel nut, but no rot was in evidence. 
Control rows produced medium-sized sound tubers, and they showed no 
signs of damping-off or wilt throughout the growing season. 
There was no perceptible difference in the response of the two varieties 
of potatoes used. However, the severity of the attack of the two fungus 
strains differed somewhat in this experiment. Thus on June 24 (five 
weeks after planting), all plants inoculated with Sclerotium No. 126 
were either dead or showed distinct symptoms of wilt, while among 
those inoculated with Sclerotium No. 127, six plants still were apparently 
unaffected, three of each variety. On July 14 wilt appeared in an ad¬ 
ditional Bliss Triumph plant; but the other five plants, three Irish Cob¬ 
blers and two Bliss Triumphs, while under size, showed no other signs 
of the disease and remained alive as long as the control plants. 
* Numbers of the cultures in this paper have reference to the writers’ collection. 
