Family Solanaceae 313 



above ground. It is characterized by a mottled ap- 

 pearance of the leaves (fig. 58 g). The portions 

 which are lighter in color seem to be thinner than 

 those which are of a normal green. In advanced 

 stages, brown spots of dead tissue may take the place 

 of the light colored mottled leaf areas. 



Mosaic undoubtedly reduces the yield, the losses 

 often amounting to twenty per cent. The Green 

 Mountain seems to be very susceptible to mosaic, 

 while the Irish Cobler seems to be especially resistant. 

 It has been proven by Worthley' that the disease is 

 carried with the tubers from diseased vines. As a 

 matter of precaution these tubers should not be used 

 for seed. Long before digging, the field should be 

 carefully inspected, and hiUs which show mosaic 

 infection should be pulled out and removed. This 

 will prevent tubers from diseased plants from being 

 mixed with healthy ones. 



Arsenical Injury 



Potato foliage is often injured when the plants are 

 sprayed with Paris green. Within a few days dead 

 spots similar to those occurring in early blight ap- 

 pear on the surface of the leaves. To obviate this, 

 lime should be added to the Paris green. If the 

 Paris green is used dry, one pound of powdered lime 

 should be mixed with each half potmd of Paris green. 

 The same proportions are used when Paris green 

 is appUed as a spray. 



Pox or Pit (fig. 60) see Sweet Potato, p. 152. 



' Worthley, E. I., Science, N. S., 42 : 460-461, 1915. 



