16 DISEASE RESISTANCE OF POTATOES. 



however, seems to be of less consequence than it is with the blight, for 

 while one of the least resistant is Dabersche, an old standard, one of the 

 most resistant is Richters Imperator, also an old variety. Other 

 varieties reported as preeminently scab resistant are Irene and Pro- 

 fessor Wohltmann. Boncza and Pomerania are reported resistant, 

 but to a less deo-ree. Seed of all these have been secured for trial in 

 this country. Early Rose is found especially liable to scab there as it 

 is in America. It will be better, however, to postpone the discussion 

 of resistance to scab as shown by American varieties of potatoes until 

 the latter part of this publication. 



OTHER SCAB-LIKE DISEASES. 



Rhlzoctonia. — This was seen on potato tubers in Europe even more 

 commonly than it occurs in America, but most European pathologists 

 regard it as nonparasitic. Those who consider it as a facultative para- 

 site attribute little injury to it generally, although some think it capable 

 of causing rot, as described ))v Frank." 



Sjwngospora solani Brun. — This fungus is said^ to cause a scab-like 

 disease in the north of Europe. This disease occurred'" to a consider- 

 able extent on potatoes secured by the writer's order from Groningen, 

 Holland. 



Superficial scurv}^ diseases attributed to other fungi occur in Europe. 

 Frank ^ describes one such caused by Phellomyces sclerotiophorus^ but 

 Doctor Appel told the writer that this had not proved serious in Ger- 

 many. Johnson ^ reports it as causing some trouble in Ireland. In 

 England another scurf disease of somewhat similar appearance is attract- 

 ing attention. It occurred on the P^ldorado seed potatoes imported 

 with our order from Scotland, and the cause is apparently the fungus 

 Spicaria nivea Hors.-' 



Oedomyces leproides Tvahut. — This is a fungus^ which attacks the 

 young sprouts or eyes of the tubers, stimulating them to abnormal, 

 cauliflower-like growth, of which the dark color has given rise to the 

 popular name black-scab. The writer did not see this disease on the 



«Kampfbuch, p. 194. 



&Ibi<l., p. 176. 



c Found and identified by James Birch Rorer. 



'^Kampfbuch, p. 182. 



« Johnson, T., The Diseases of the Potato and Other Plants in Ireland, Journal, 

 Dept. Agric. Ireland, Vol. Ill, No. 1 (1902). 



/ So identified by Dr. Ernst A. Bessey. Dr. Thomas Milburn, of the Midland Agri- 

 cultural and Dairy Institute, England, advises the writer by letter that he is engaged 

 in a special study of this disease. He finds it to occur on most English varieties, 

 Evergood and Sutton's Flourball being by far the worst, while East Anglian and 

 Sutton's Discovery are the only ones he has found entirely free from it. 



9 This also occurs on beet roots. See M,assee, Geo. A., Textbook of Plant Diseases, 

 p. 225. 



