POTATO INSECTS 153 



fruits. The blossoms are killed, the fruit is dwarfed and the 

 ripening period is delayed so that in many cases the crop is a 

 total loss. 



Control. 



The potato aphis can be killed by spraying with "Black 

 Leaf 40" tobacco extract, ^ pint in 50 gallons of bordeaux 

 mixture. If for any reason bordeaux mixture is not used, the 

 "Black Leaf 40" may be diluted with water at the same rate 

 but in this case 3 or 4 pounds of soap should be added to each 

 50 gallons. Since many of the aphids are on the underside 

 of the leaves, it is necessary to have the spraA' directed upward. 

 Some potato-sprayers have the nozzles arranged to do this. 

 Other potato-sprayers may be adapted for this work by remov- 

 ing the nozzles and inserting a 1-foot extension directed down- 

 ward. On the end of this extension a T-coupling is attached. 

 To each side of the T-coupling is joined a piece of pipe 6 inches 

 in length directed at right angles to the rows and equipped 

 with a 45° angle nozzle, so attached as to throw the spray 

 obliquely upward and backward. This outfit can be used to 

 advantage as long as the plants are upright. After the vines 

 are down, effective work can be done by using two leads of hose 

 10 or 12 feet in length equipped with 4-foot extension rods 

 and angle nozzles. With this outfit a traction pump will not 

 deliver the liquid in sufficient quantity and it is, therefore, 

 necessary either to operate the pump by hand or with a gaso- 

 line engine. It requires at least 100 gallons of the spray mate- 

 rial to the acre to be effective. It is usually better to use the 

 tobacco extract in combination with the bordeaux mixture 

 than with water and soap because of the value of the bordeaux 

 in preventing potato blight. Furthermore, it has been ob- 

 served that potatoes regularly sprayed with bordeaux mixture 

 are less likely to be seriously infested with the aphid than un- 

 treated vines. Where there is anv reason to fear an outbreak 



