420 Report of the Mycologist of the 



On all of the plats the potatoes came up well and produced a 

 luxuriant growth of foliage. When the crop was harvested it 

 was found that some of the tubers had rotted although the plants 

 had received two applications of Bordeaux mixture, but the loss 

 from rot was too small to materially affect the results so far as 

 amount of scab is concerned. 



It was found that the total yield of the three plats on which 

 rye had been plowed under was 1891 pounds, while the total 

 yield of the three plats which had no rye was 2135 pounds. The 

 smaller yield on the rye plats appears to have been due to the 

 rye. At least, it is safe to say that the rye had no tendency to 

 increase the yield. 



With reference to the amount of scab, the tubers were sorted 

 into three classes: (1) Those entirely free from scab, (2) those 

 which were scabby but merchantable, and (3) those which were 

 so scabby as to be unmerchantable. The total yield of 1891 

 pounds on the rye plats was divided among these three classes as 

 follows: No scab, 526 pounds; scabby but merchantable, 572 

 pounds; unmerchantable, 793 pounds. Classified on the same 

 basis the yield of the plats without rye was distributed as fol- 

 lows: No scab, 785 pounds; scabby but merchantable, 661 

 pounds; unmerchantable, 689 pounds. From these figures it will 

 be seen that plowing under rye did not decrease the amount of 

 scab in the least, but on the contrary apparently increased it 

 considerably. 



From the results of this experiment, then, it appears that the 

 practice of plowing under green rye to prevent potato scab is 

 not to be recommended, inasmuch as it tends to increase rather 

 than decrease the amount of scab and may, perhaps reduce the 

 yield. 



Concerning the value of the corrosive sublimate treatment, 

 different plats gave different results, but on the whole the treated 

 were fully as scabby as the untreated. This has been the almost 

 universal experience and our experiment only serves to empha- 

 size the uselessness of treating the " seed " with corrosive subli- 

 mate, if it is to be planted in scab-infested soil. The corrosive 

 sublimate treatment did not reduce the vield. 



