32 MAINE AGRICULTURAL EXPERIMENT STATION. 



A reasonable explanation of the failure of sulphur tO' produce 

 results in this instance, and also in the unsterilized pots of soil 

 mentioned above, comes from the fact that the scabby tubers 

 were found in those parts of the pots outside of the area of 

 soil into which the sulphur was introduced. 



The chief value of these greenhouse experiments lies in the 

 fact that they were carried out under control conditions — they 

 are far too limited to admit of any definite conclusions. They 

 do, however, suggest certain things of practical interest, the 

 most important one of which comes from the results obtained 

 where sulphur was used with scabby seed on clean or sterilized 

 soil. This is, that the practice recently adopted by some of our 

 potato growers of dusting cut seed with, or rolling it in, sulphur, 

 is a good one and should be encouraged. If the seed tubers 

 are first carefully sorted, then disinfected with corrosive sub- 

 limate or formaldehyde, cut and dusted with or rolled in sul- 

 phur, it would seem as if the danger from the introduction of 

 common scab into clean land by means of seed tubers would be 

 practically eliminated. 



A close analysis of the results of these greenhouse experi- 

 ments does not tend to encourage the view that sulphur can be 

 used economically to rid badly infested soils of the germs of 

 common potato scab. However, in this and in most other ex- 

 periments no account of the later effects of sulphur in the soil 

 are taken into consideration and it hardly seems possible that 

 the entire effects are obtained the first year. Hence the case 

 may not be entirely hopeless. 



Field experiments designed to test matters of this kind are 

 not easy to perform, as it is next to impossible to get any large 

 body of land equally infected and alike in all other particulars. 

 An attempt was made to carry on such an experiment in coop- 

 eration with an Aroostook county potato grower last season. 

 Seven half-acre plots were laid off on one side of a large field 

 where the land was said to be fairly uniformly infected with 

 common potato scab. A plot of Green Mountains and one of 

 Irish Cobblers were treated at the rate of looo pounds of sul- 

 phur per acre, harrowed in before planting. These were fol- 

 lowed by an untreated check plot of equal size and this by plots 

 of Cobblers, side by side with untreated checks, where 500 and 

 300 pounds of sulphur were added respectively. 



