Feb. 21, 19x6 
* Soilstain , or Scurf, of Sweet Potato 
997 
STORAGE EXPERIMENTS 
Growers who do not suspect the fungous nature of soilstain are always 
at a loss to explain the appearance of the trouble in storage when other¬ 
wise healthy roots are brought in. In order to determine definitely the 
effect of storage on this disease, the following experiments were carried 
out during two consecutive seasons: At digging time in September, 1913, 
a diseased field was chosen for that purpose. A large number of roots 
were selected and placed in hampers in the following ways. 
Experiment 1.—Three hampers were filled with roots which to all 
appearances were free from stain. The object of the experiment was to 
determine whether apparently clean roots taken from a diseased field 
will develop stain. 
Experiment 2.—Three hampers were filled with roots which showed 
very slight infection. The spots in these cases varied from 5 to 10 
in number and were single and scattered. The object of this experiment 
was to determine whether the disease would increase in storage and the 
spots coalesce. 
Experiment 3.—Three hampers were filled with roots which were 
thoroughly stained all over. The object of this experiment was to deter¬ 
mine whether badly affected roots would be subject to more rapid drying 
and shrinkage. 
Experiment 4.—Three hampers were filled with well-stained roots. 
At the bottom was placed a layer of stained roots, followed by a layer of 
healthy ones, on top of which was another layer of stained roots. Each 
layer was separated from the other by a narrow strip of paper. The 
object of this experiment was to determine whether healthy roots in 
contact with diseased ones will become infected under storage conditions. 
Experiment 5.—Three hampers were filled with roots which to all 
appearances were free from stain and were taken from an adjoining clean 
field. These were to serve as checks. 
All the experimental hampers were placed in a medium-sized potato 
house which had poor facilities for ventilation. The conditions, there¬ 
fore, were ideal for the experiment. The hampers were stored for a 
period of 5^ months. 
The results of the above experiments may be summarized as follows: 
The roots in the first three hampers (experiment 1) remained clean, indi¬ 
cating that clean roots, though coming from an infected field, when 
stored and protected from contact with stained roots, will remain clean. 
The roots in the second three hampers (experiment 2) showed an increase 
in the stain and a coalescence of previously smaller spots. The roots in 
the third three hampers (experiment 3) seemed to be shrunken most. 
The roots in the fourth three hampers (experiment 4) indicated that 
apparently healthy potatoes may become stained when placed directly 
in contact with diseased roots. The check roots (experiment 5) were all 
free from stain. The above experiments were repeated in 1914 and 1915. 
The results obtained did not differ from those referred to above. 
