Insects in General 



Sprayers 



Sometimes arsenical poisons burn the leaves of plants, especially 

 if the application is heavy. This is due to free arsenious acid in the 

 material used. The addition of a little quick lime to the water in which 

 the poison is mixed will prevent this burning. When lime has been 

 added the solution must be carefully strained to remove particles of lime 

 which would otherwise clog the nozzles. 



Control of Sucking Insects — Contact Poisons 



In the control of sucking insects the contact poisons kill the insects 

 either by corroding their bodies or by clogging their spiracles, thus 

 causing strangulation. Black-leaf 40 (See page 114), kerosene emulsion 

 (See page 1 14), the so-called insect powders and soluble oils are standard 

 remedies for sucking insects. As the name implies, these substances 

 must come in actual contact with the insect to kill it. 



Repellents 



A repellent is any substance the presence of which on plants makes 

 them so distasteful to insects that they will not feed upon them. Mix- 

 tures containing tobacco preparations or soap, especially whale oil soap, 

 are effective as repellents. 



SPRAYERS 



A. TRACTION SPRAYER 



For field use any one of the many makes of traction sprayers (Fig. 

 I, Page 33) is recommended. 



Fig. 1. A Good Type of Traction Sprayer for Field Use 



33 



