POTATO 267 



Insects. There are but few insects that do serious 

 injury to the potato in this section, and the most impor- 

 tant of these is the Colorado potato beetle or "potato-bug," 

 but it may also be injured by blister beetles, wire worms, 

 and white grubs. (For remedies for these pests, see 

 chapter on insects.) 



Diseases. There are several diseases that sometimes 

 injure the potato. The most common of these are known 

 as the scab and the blight. Scab is a term used to refer 

 to the rough patches with which potatoes are frequently 

 covered. Potatoes so infected are lessened in yield, and 

 on account of being unsightly and rough do not sell readily. 

 The term blight refers to a disease that kills the tops. 



Scab of potatoes is caused by a fungous plant working 

 in the surface of the potato. The germs of it are very 



Fig. 116. Potato scab. Both groups were grown from the same lot of 

 scabby seed, those on the left from treated seed; those on the right, untreated. 



abundant and live for many years in the soil and also 

 over winter on the potatoes. If these germs are fed to 

 stock they undoubtedly grow in the manure, and the use 

 of such manure may often be the cause of infection. Also 



