356 . GARDEN FARMING 



Potato scab. The next most serious enemy of the potato is the 

 potato scab, which is shown on the tubers in figure 128. Scab, 

 which appears as rough, somewhat corky spots upon the surface of 

 the tubers, is the result of a fungus which lives from year to year in 

 the soil and on stored tubers, and is communicated to the new potato 

 from the seed or soil, as the case may be. The common method of 

 dealing with this disease is to treat the seed previous to planting it, 

 but do not mistake the small, corky lenticels which are characteristic 



FIG. 128. Scabby tubers 



of some varieties for the irregular rough, scabby spots which are 

 characteristic of this disease. The common method of handling the 

 seed is to soak it for two hours, prior to cutting or planting, in a 

 solution of I pint of formaldehyde (or formalin) to 30 gallons of 

 water, or to soak the seed for i^- hours in a solution of bichloride 

 of mercury, 2 ounces to 16 gallons of water. The bichloride of 

 mercury, while undoubtedly quite as effective as the formaldehyde, 

 is less easily handled and is not sufficiently less expensive to 

 justify the substitution of one for the other. The bichloride 

 of mercury, or corrosive sublimate, is a deadly poison and more 



