POTATOES. 



259 



this, scabby potatoes should be dug- at once when matured, since, 

 otherwise, the scab will continue to grow and to cause an increase 

 of the injury. 



Another instance showing- 

 the germ character of the po- 

 tato scab and that it will live 

 over in the soil was related to 

 me by a gentleman from 

 Edina Mills, Hennepin coun- 

 ty, it having occurred on his 

 farm in 1891. 



He had a piece of land on a 

 hillside, through which is a 

 slight depression extending- 

 down the hill near the center 

 of the piece. The potatoes 

 on this land had been scabby 

 and he thought it bestto dis- 



Fig. 2. Sketch of two potatoes SllOWing tlie pr.nti'nnp o-rowJno- tVi^tTi r.n i + 



effects of artificial applicatiou of the germs of contmue growing ttiem on it, 

 -deep scab." In the case of the lary;e tuber and, instead, broke up a 

 the germs were taken from a pure culture and . . , , . 



applied in the form of an L. The apex of the piece of land JUSt below and 

 small tuber was merely brushed with water con- 1 i. J •- ^ rintafnp« At 

 taining germs. Natural size. After BoUey. piantea it to potatoes. iit 



harvest he found that, ex- 

 tending- down the hill in the form of the letter V, where the drain- 

 age from the land above would naturally flow, that the potatoes 

 were scabbj^, while on the rest of the piece the tubers were clean 

 and sinooth. This is illustrated in figure 3, in which A represents 



Fig. 3. Showing distribution of potato scab by drainage. The enclosure to the 

 right and above is land infested with potato scab. The enclosure to the left and be- 

 low is the newly broken land which was planted with clean seed potatoes. The V 

 shaped part below the fence represents the part of the new land infected with scab 

 from the tieid above by drainage 



the land that produped scabby potatoes, B the new land that was 

 newl}' broken up and C the portion of B which received the wash 

 from the land above it, which, consequently, was infested with scab. 



Our largest and most experienced potato g-rowers take great pains 

 to obtain and plant only such seed potatoes as are free from scab, 

 and not to plant on land that has produced a crop of rough potatoes. 

 These considerations are the result of constant observation of the 

 evil attendant on such practices. 



Extensive experiments made at this Experiment Station and in 

 many places elsewhere show plainly: (1) That scabby seed potatoes 

 almost uniformly produce a scabby crop of tubers, even if planted 



