SPECIAL REPORT FOR YEAR I9I4. 31 



The fungicidal properties of sulphur are well known. More- 

 over, the chemical compounds which would be formed as the 

 result of the addition of sulphur would tend to develop acidity 

 in the soil which of itself is unfavorable to the common potato 

 scab organism. Experiments conducted in New Jersey some 

 years ago indicated that it was of value, at least under some con- 

 ditions, as a soil disinfectant for common scab. It can be pur- 

 chased in ton or carload lots at a considerable less price than 

 the same amount of fertilizer. Therefore it seemed to be a 

 favorable material with whieh to experiment. 



The present discussion is limited to the use of sulphur on 

 soil contaminated with the germs of the common scab and is not 

 concerned with the use of sulphur for other soil-inhabiting 

 potato diseases. Certain greenhouse experiments, although 

 necessarily conducted on a small scale, gave some rather inter- 

 esting results. Sulphur was added to loinch pots of greenhouse 

 soil, well contaminated with scab germs, at the rate of 300 

 pounds per surface acre. This was mixed only with the soil 

 immediately surrounding the seed tuber, simulating as far as 

 possible the application in the hill by means of a planter. Some 

 of the pots of soil were sterilized to make them comparable to 

 clean land. Scabby seed tubers were planted in this, with and 

 without sulphur. At the same time disinfected and undisin- 

 fected scabby seed tubers were planted in other pots of unster- 

 ilized soil, with and without sulphur. 



When the seed was scabby, the soil not sterilized, and no sul- 

 phur was used, 100 per cent of the crop was scabby. The addi- 

 tion- of sulphur in the manner described reduced the amount of 

 scab but slightly. Sterilized soil and scabby seed gave 30 per 

 cent of scab on the crop, while perfectly clean potatoes were 

 secured with the same sterilized soil and scabby seed where sul- 

 phur at the rate of 300 pounds per acre was mixed with the soil 

 immediately surrounding the seed-piece. Apparently this amount 

 of sulphur was sufficient, when applied in this manner, to pre- 

 vent the disease from spreading from the infected seed-piece 

 to the crop, but not enough to materially reduce it where the 

 soil itself was badly contaminated with the germs of the disease. 



Some pots of fresh greenhouse soil were planted with scabby 

 seed tubers, disinfected with formaldehyde, with and without 

 the addition of sulphur to the pots. In this case there was an 

 average of more scab where the sulphur was used than without. 



