2o6 DISEASES OF THE SWEET PEA 



pests are best controlled by the use of poi- 

 sonous mixtures applied in the form of 

 liquid sprays or powders. Insecticides 

 may be classified as internal or stomach 

 poisons, and external or contact poisons. 

 The former kill the biting insects which 

 take it into the stomach with the food; the 

 latter kill by direct contact, and either 

 causes an irritation of the surface of the 

 body or clogs the respiratory openings of 

 sucking pests. 



(a) Stomach Poisons. Paris green is 

 one of the best known of stomach poisons. 

 When chemically pure, it is composed of 

 copper oxide, acetic acid, and arsenious 

 acid. It destroys cutworms, caterpillars, 

 beetles, grubs, slugs, etc. On the sweet 

 pea it should be applied preferably as a 

 liquid, using one pound of the poison and 

 one pound of lime to two hundred gallons 

 of water. Paris green tends to sink to the 



