131 



Irish Potato Scab (Oospora scabies) as Affected by 



Fertilizers Containing Sulphates and 



Chlorides. 



S. D. Conner. 



In the spring of 1911 a pot experiment with Irish potatoes was started 

 at the Purdue Experiment Station by the autlior. It was the intention to 

 investigate the composition and quality of potatoes grown in several types 

 of soil with different fertilizers, the ordinary silt loam of the station farm 

 being the principal soil used. Peat and sandy soils were also used, as 

 well as eight pots containing pure silica sand. The principal fertilizers 

 studied were sulphate of itotash and chloride of iiotash. Two varieties of 

 potatoes were used, Early Ohio, one of the best early varieties, and 

 Carmen No. 3, a good late variety. 



The exi)eriment was not planned to cover an investigation of potato 

 scab, although this development of the research may be one of the most 

 significant features noted. The seed potatoes planted the first, year did 

 not show any scabbiness and no attempt was made to prevent it. When 

 the potatoes were harvested, however, it was seen that formalin should 

 have been used, as the crop was badly affected by the sc-ab fnngiis Oospora 

 scabies. The scab was very much worse in the brown peat than in the 

 other soils, as will be seen from Fig I. There was also a slightly greater 

 amount of scab in the pots where chloride of potash was used than there 

 was where sulphate was used, the unfertilized pots being affected the 

 worst of all. In 1912, to prevent scab the seed potatoes were all treated 

 with formalin and one-half the pots, which are in duplicate, were given 

 an application of flowers of sulphur, which is a treatment that has been 

 reported as a success by certain investigators.* No great differences as to 

 scabbiness were seen in the crop of 1912, and photographs were not taken. 



In 1913 the seed potatoes were again treated with formalin, Ijut no 

 sulphur was added. When the potatoes were harvested this year a sur- 



* B. D. Halsted, Bui. 112, N. J. Agr. Exp. Sta.; also Bui. 120 N. J. Exp. Sta. 



