No. 4.] MODERN POTATO CULTURE. 57 



Long-continued cloudy and damp weather, followed by sev- 

 eral hot and bright days, is apt to result in the burning of 

 the foliage. Leaf burn may also occur as the result of pro- 

 tracted dry weather. 



Leaf poisoning or burning may occur where Paris green is 

 applied to potatoes, and frequently it cannot be distinguished 

 from early blight by an ordinary examination. It some- 

 times happens, therefore, that farmers are led to believe 

 that their potatoes are affected with early blight and other 

 diseases when the trouble has been brought on by themselves 

 through the improper use of Paris green. Injuries result- 

 ing from the use of this substance are very apt to occur 

 where flea beetles have eaten the foliage. The arsenic at- 

 tacks the tissues at .such points, and as a result more or less 

 circular brown spots are produced, having for their centres 

 the holes eaten by the flea beetles. By combining the Paris 

 green with Bordeaux or with lime, these injuries may be 



avoided. 



Potato Scab. 



Scab is one of the most wide-spread diseases affecting the 

 potato, and is unfortunately too well known to need de- 

 scription. While injuries of various kinds produce a rough- 

 ened surface, which is sometimes mistaken for scab, it is 

 safe to say that nine-tenths of what is known as scab is due 

 to the attack of a minute fungus first studied and described 

 by Dr. Thaxter, at that time mycologist to the Connecticut 

 Experiment Station. The fungus will live in infested soil 

 for years, and once established it is well nigh impossible to 

 get it out of the land. Every precaution should be taken to 

 keep land free from this disease. The most likely sources 

 of contamination are potatoes used for seed, although farm 

 manures may become a source of contamination, usually 

 because of scabby potatoes or roots which have been fed to 

 stock or added to the compost heap. All potatoes used for 

 seed, whether apparently affected with scab or not, should 

 before being cut be treated with a weak solution of corro- 

 sive sublimate (formula 1) or formaline (formula la) and 

 then spread out to dry. After drying, the potatoes may be 

 cut and planted in the usual way, care being taken not to 



