CHAPTER IV 



INSECTICIDES AND THEIR USES 



The most approved means of controlling insects consists in 

 the use of poisonous mixtures administered in the form of a 

 spray, wash, or dry powder in conjunction with such methods of 

 farming, as fall plowing and rotation of crops, which tend to 

 decrease the chances of injury from insect attack. 



Insecticides, or the substances used for the destruction of in- 

 sects, may be classified as internal or stomach poisons, and ex- 

 ternal or contact poisons. The former kill by being eaten with 

 the insects' food, the latter by direct contact causing corrosion 

 of the bodies of the insects, or the closing of their breathing 

 pores. 



STOMACH POISONS, ARSENICALS, ETC. 



Paris green. — Of the various internal poisons in use against 

 insects none are so valuable or so much used as Paris green,* 

 the standard remedy against biting or chewing species, which 

 include the bulk of injurious forms, such as cutworms and other 

 caterpillars, beetles, grubs, slugs, etc. Paris green is applied in 

 two ways, — dry and as a spray, the latter being the method 

 most extensively used, as it is cheaper and more effective, 

 answering all the purposes to which dry powders are put. A 

 spray is prepared by combining one pound each of the poison 

 and fresh slaked or quick lime with from 75 to 150 gallons 

 of water. A slight excess of lime is advisable. A somewhat 



1 Paris green is now chemically known as copper accto-arsenite ; in other 

 words, it is a chemical compound of oxid of copper, acetic acid and arsenious 

 acid, and when properly combined the proportions of the different chemicals 

 are as follows: copper oxid, 31.29 per cent.; acetic acid, 10.06 per cent.; 

 arsenious acid, 58.65 per cent. 



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