100 M.\INE AGRICULTURAL KXPE;RIMLNT STATION. I914. 



that manure of a pig fed with potatoes affected with powdery 

 scab carried the germs of the disease. Certain other writers 

 have pointed out the fact that contaminated manure may be a 

 means of spreading the infection. 



It is claimed that healthy potatoes which have been in con- 

 tact with diseased ones may carry powdery scab. This naturally 

 leads to the supposition that it may be spread by mean of sacks 

 or other containers or by means of tools such as planters, etc. 

 Another possibility is that plows, harrows or other tools used 

 for working infected land may carry with them the germs of 

 the disease to contaminate portions of the farm now free from 

 powdery scab. Little data are to be had on this phase of the 

 subject and until we know more about the matter the possibility 

 of spreading the disease in this way should be kept in mind 

 and guarded against as far as possible. 



Preventive Measures to be Employed against the Disease. 



For the length of time powdery scab has been known it is 

 surprising how little has been done toward solving the problem 

 of its control and eradication as indicated by published work. 

 So far as the writer has been able to ilearn Doctor Pethybridge 

 of Ireland is about .the only investigator who has conducted ex- 

 periments along the line of soil and seed treatment. 



Speaking of work done in 1909 Dr. Pethybridge says,* 

 "Experiments on treating afifected seed potatoes with disinfec- 

 ants showed that such seed, if planted subsequently on clean 

 land, gave a clean crop after steeping for two or three hours in 

 a solution of formalin (formaldehyde) at the rate of half a pint 

 of 40 per cent formalin in fifteen gallons of water " 



The following year he gives the details of several new experi- 

 ments t. Seed only slightly affected gave over 54 per cent of 

 the crop scabbed, and 67 per cent of the crop was diseased 

 where badly affected seed was used. Soaking in formaldehyde 

 one part to 600 for 3 hours reduced the amount of scab to 2.6 

 per cent, showing a high degree of efficiency. Wetting the 

 surface of the tubers and rolling them in flowers of sulphur 

 eliminated all of the scab except about one per cent. A one 



* Jour. Dep. Agr. and Tech. Inst. Ireland 10 : 254-256. 1910. 

 t Jour. Dep. Agr. and Tech. Inst. Ireland 11 : 26-29. 1911. 



