274 



CONTROLLING INSECTS AND DISEASES 



He should base his decision on known facts in order to 

 proceed with judgment and with as little risk as possible. 



Procedure : 



(a) Consider materials for insect control. 

 (6) Consider materials for disease control. 



(c) Consider agents that increase spreading and sticking quali- 



ties of materials for insect and disease control. 



(d) Consider preparation of materials at home or their pur- 



chase from commercial concerns. 



(e) Select materials for a complete program. 



(a) Consider Materials for Insect Control. Materials 

 used to control insects are termed insecticides. For biting 

 and chewing insects, a stomach poison is applied to the mate- 

 rial on which they feed. 



For sucking insects, materials which suffocate, burn, or 

 paralyze them are used. These are called contact insecticides, 

 since they are applied directly to the bodies of the insects. It is 

 evident that a stomach poison applied on the exterior surfaces 

 of the materials on which sucking insects feed would not prove 

 effective. 



Insects with lapping mouth parts may usually be controlled 

 with stomach poisons since they take up their food from the 

 outer surfaces. 



Stomach Poisons 



a: 1. Lead arsenate is the stomach poison in common use. 

 Its active agent is white arsenic. White arsenic alone will 

 cause burning of fruit and foliage; it is therefore combined with 

 lead to reduce this danger. 



Lead arsenate is known as ^^acid,^' or ^^basic," depending 

 upon the nature and proportion of the lead-carrying material 

 combined with the w^hite arsenic. The acid lead arsenate is in 

 more common use and is sometimes called '^standard'' arsenate 

 of lead. Basic lead arsenate contains less arsenic, is more 

 stable and less likely to cause burning, but is slower in its 



