156 MAINE STATE COLLEGE 



Potato and Beet Scab. 

 Oospora scabies, Thaxter. 



The scab of potatoes and beets has been quite prevalent the past 

 season. The ordinary disease of potatoes and beets known as 

 "scab" has been demonstrated by Dr. Thaxter to be due to the 

 same fungus, the species named above. Now that the cause is 

 known experiments for checking the disease can be conducted upon 

 a rational basis. Professor Bolley exhibited at the World's Fair, 

 Chicago, in the exhibit of the office of experiment stations, two 

 jars of potatoes grown under similar conditions from scabby seed. 

 One lot was treated with a dilute solution of corrosive sublimate 

 and the other lot was untreated. The former lot was comparatively 

 free from scab and well grown. The latter badly scabbed and 

 dwarfed. 



This would indicate that scabby seed may be the cause of the 

 disease and that clean seed should be planted. It would also fol- 

 low that scabby seed treated will produce much better potatoes than 

 scabby seed untreated. 



We feel positive that the disease cannot be controlled merely by 

 planting clean seed. The last season we planted clean seed upon 

 soil that had not grown potatoes for two years and raised a badly 

 scabbed crop. It seems certain that this disease may live in the 

 organic matter of the soil even more than one year or else has other 

 hosts which have not been discovered upon which it maintains itself. 



Will treating clean seed with corrosive sublimate give a better 

 crop than clean seed untreated ? If not we see no great use for it, 

 for clean seed is usually obtainable. 



Experiments to show the vitality of this fungus in soil not grow- 

 ing potatoes are desirable in order to learn whether a system of 

 rotation may not clean the soil of the disease. Experiments should 

 be conducted with clean seed upon grass lands in order to learn 

 whether they are free from the fungus and settle the question 

 whether newly turned grass land is better for potatoes. The study 

 of fertilizers in relation to the introduce ion of this disease is im- 

 portant. Considerable more study upon the conditions of growth 

 of this fungus is necessary. 



