POISON INSECTICIDES n 



^ The kind of insecticide used will depend upon the 

 kind of mouthparts the pest has, whether biting or 

 sucking. 



It will also depend somewhat upon the life his- 

 tory and habits of the pest. 



There are two main kinds of insecticides. — (a) 

 Poisons for biting insects; (b) contact substances 

 for sucking insects. Gases are also used for both 

 biting and sucking insects. 



POISONS FOR BITING INSECTS 



Several forms of arsenical poisons are used for 

 killing insects that eat the foliage of plants. Ar- 

 senate of lead, however, is more universally used 

 in orchard work than any of the others. The fol- 

 lowing are some of the poisons employed : 



1. White arsenic. 



2. Paris green. 



3. Arsenate of lead. 



4. Arsenate of calcium. 



5. Arsenite of zinc. 



6. Arsenite of lime. 



7. Arsenite of copper. 



8. London purple. 



9. Paragrene. 

 10. Hellebore. 



Arsenic 



White arsenic (AS2O3) is a white heavy powder 

 and the cheapest form of a poison insecticide. Un- 

 fortunately, it is soluble in water and therefore will 

 burn foliage. It can be used in combination with 

 lime or Bordeaux mixture, however, if the proper 

 precautions are taken. 



In the following formulas the arsenic is com- 

 bined with lime and the material is known as arsen- 

 ite of lime. 



