Aug. 21, 1916 Control of Powdery Dryrot 0} Potatoes 829 



in storage, and one sack each of bruised and sound tubers was dusted 

 with lime and put in storage. On September 28, twenty-four hours 

 after digging, the second lot, consisting of five sacks each of bruised and 

 sound tubers, was treated in the same manner as that of the previous 

 day and placed in storage. On September 29, forty-eight hours after 

 digging, the third lot, consisting of five sacks each of bruised and sound 

 tubers, was treated in the same manner as the first and second lots and 

 placed in storage. On September 30, seventy-two hours after digging, 

 the fourth lot, consisting of five sacks each of bruised and sound tubers, 

 was treated in the same manner as lots 1,2, and 3 on previous days and 

 placed in storage. On October 1, ninety-six hours after digging, the 

 fifth lot, consisting of five sacks each of bruised and sound tubers, was 

 treated in the same manner as those on the previous days and was put in 

 storage. In each case the disinfected potatoes were stored in the sacks 

 in which they were disinfected. In order to give the experiment a 

 severe test all five lots were stored for about six weeks in the anteroom of 

 the storage cellar, where temperature and moisture conditions were 

 favorable for dryrot development, after which they were transferred 

 to the storage cellar proper. 



On April 1,2, and 3, 1916, examination of the potatoes was made. 

 Each tuber was carefully examined to determine the presence or absence 

 of decay. Wherever decay occurred, typical specimens were taken to 

 the laboratory, and the presence of F. trichoihecioides was determined by 

 means of artificial cultures. All of the unbruised tubers, whether disin- 

 fected or not, were still wholly sound. The bruised tubers which were 

 not disinfected presented essentially the same appearance in all lots. 

 Those with deep bruises were usually from one-third to totally decayed. 

 Those with shallow bruises in some cases showed no decay, but the majority 

 showed at least slight decay. By "deep bruises" are meant those which 

 penetrated the tuber tissue far enough to be partly closed up and covered 

 over when the digging instrument was withdrawn; by "shallow bruises," 

 those which were only skin deep, or which presented a comparatively 

 clean cut surface. The condition of the disinfected, bruised tubers at 

 the end of the storage period is shown in Table IV. 

 52171°— 16 3 



