POTATOES 355 



destruction caused by the beetles. There are other insecticides, 

 such as London purple and arsenate of lead, which are used to a 

 considerable extent. 



Flea beetles. These frequently invade potato fields in vast num- 

 bers, attacking the leaves and causing innumerable tiny holes to ap- 

 pear. In infested regions, when systematic spraying for the control 

 of blight by the use of Bordeaux mixture is carried out, it is a well- 

 known fact that injury from flea beetles is decidedly less. It is 

 fortunate that the treatment for the control of the blight is also a 

 satisfactory and economical treatment for this form of insect pest. 

 Probably the most economical method of treatment is to combine 

 the spray for the insect pests with the treatment for the blight, 

 which is one of the most injurious potato diseases with which we 

 have to contend. 



Blights. There are different diseases called blight. The early 

 blight, which causes the foliage to turn yellow and assume an abnor- 

 mal condition, results in the death of the plant before its proper sea- 

 son of ripening. There is another blight, known as the late blight, or 

 rot, which affects the leaves and, if not prevented, causes the tubers 

 to rot very quickly after the plants have become infested. These 

 different forms are not common to all potato-growing sections ; 

 the early blight is more serious in the North, while the late blight 

 is more serious in the early-potato-growing regions at the South. 



The treatment which has proved most effective in the control 

 of the potato blights consists of frequent applications of Bordeaux 

 mixture. The early application may be combined with Paris green 

 or London purple for the destruction of the Colorado beetle. Even 

 after the necessity for the use of the poison has ceased, the plants 

 should be sprayed at intervals of a week or ten days throughout 

 the growing period, depending upon the weather. In some sections 

 five treatments seem to suffice, while in others as many as seven 

 are found profitable, and even necessary, for the production of a 

 successful crop. Both Paris green and Bordeaux mixture are now 

 applied with power sprayers arranged to spray both the top and 

 lower sides of the leaves at the same time, the pump being worked 

 by gear driven from the wheels of the spray cart. There are vari- 

 ous forms of such devices, some spraying as many as eight rows 

 at one trip across the field. 



