FUNGOUS DISEASES AND SPRAYING 67 



$15.50. Much larger savings are often reported ; in 3'ears 

 wlien the late blight and rot are prevalent it is not unusual for 

 sprayed vines to produce more than double the yield of sim- 

 ilar unsprayed ones. 



Potato Scab. Roughenins; of the skin of the tubers in 

 rounded patches or scabs, patches sometimes covering the 

 entire surface ; caused by bacteria-like organisms which may 

 be already in the soil or which are more frequently introduced 

 on the seed potatoes. 



Treatment. This consists in avoiding contaminated soil and 

 disinfection of the seed. Disinfection is accomplished by 

 soaking the seed in one or the other of the following solutions : 



Formalin . . 8 ounces. 



Water . . 15 gallons. 



.Soak tubers in this two hours. 



Corrosive sublimate 2 ounces. 



Water . . 15 gallons. 



Soak tubers in this one and one-half hours. 



The formalin is preferred as not being so poisonous nor so 

 likely to injure the seed. We have obtained good results by 

 the usejof these disinfectants. We have also found that plas- 

 ter, ashes, and stable manure favor the development of the 

 scab, if the germs are present on the seed or in the soil. 

 Potatoes should not be planted in soil that has already pro- 

 duced a scabby i'crop. 



