1913.] PUBLIC 1)()(;UMEXT — No. 31. 87 



the soil. He maintains that it not only proved to be the best 

 remedy for the scab but had a wholsome eflFect on the soil. Dr. 

 Arthur, on the other hand, found sulfur unpromising and dis- 

 continued experiments with it. His experience with sulfur was 

 corroborated by Dr. H. J. AVheeler ^ and Mr. G. M. Tucker, 

 who experimented to quite an extent with sulfur and various 

 fertilizers. They found that when sulfur was freely mixed with 

 soil badly contaminated with scab it had no appreciable effect 

 in controlling the disease, and was practically a failure. They 

 found, also, that stable manure of all kinds, wood ashes, air 

 slaked or caustic lime, carbonate of soda, potash, lime and 

 magnesia favored tlie scab. They obtained a scabless potato 

 with calcium chloride or land plaster (gypsum), and when 

 fertilizers were used without any free lime compounds no scab 

 occurred. They further observed that the marked acidity of 

 the soil or the absence of carbonates was unfavorable to scab. 

 They maintain that when the soil is favorable to the develop- 

 ment of scab, or when badly contaminated, the corrosive sub- 

 limate treatment is entirely useless as a preventive. The results 

 of Wheeler and Tucker's experiments are in accord with con- 

 ditions which we have observed in Massachusetts for many 

 years. The presence of carbonates in the soil will increase scab 

 from 2 or 3 per cent, to practically 100 per cent, in a relatively 

 short time, and the use of clean seed, or their treatment with 

 corrosive sublimate or formalin according to the formulas recom- 

 mended under these conditions, is of little value. On the other 

 hand, Avhen soils are imfavorable for the development of the 

 scab and are only slightly contaminated, formalin and corrosive 

 sublimate are very effective and have been of great value as 

 preventives of this disease. 



ExrEKIMEXTS WITH VaKIOUS CheMICALS FOE THE PREVEN- 

 TION OF Potato Scab. 



In the spring of 1908, as a result of much local complaint 

 relative to potato scab and methods of eradication from infested 

 soil, it was thought that it might be possible to treat the soil 

 with certain chemicals and in this way eradicate the trouble. 



» H. J. Wheeler and G. M. Tucker, Bui. 40, R. I. Agr. Exp. Station Rept. 1896, pp. 80-96. 



