CHAPTER V 

 INSECTICIDES AND SPRAYING 



FOR the purpose of combating insects the farmer, orchardist 

 and gardener, disregarding scientific classification, need consider 

 only two groups: 



A. Biting insects, or those which devour leaves, stems, stalks 

 of grain, grasses, and fruit. Examples of these are seen in grass- 

 hoppers, caterpillars of all sorts (including cut-worms and army 

 worms), and in beetles and so-called " slugs, " the larvae of saw flies. 



B. Sucking insects, those which pierce the surface of leaf or 

 fruit, skin of animals, and suck the sap of plants or the blood of 

 animals from below the surface. 



Manifestly two entirely different classes of insecticides are 

 necessary in combating the two groups. 



Internal Poisons. Group A calls for internal poisons, poison 

 sprays or poison baits, which taken internally result in the death 

 of the insects in question. Such poisons are found in a number of 

 forms. 



1. White arsenic or arsenious oxide (As 2 O 3 ) is soluble in water, 

 and is dangerous to both plants and human beings and hence not 

 desirable. 



2. Paris green is a combination of arsenic and copper with a 

 certain amount of free arsenic occurring in the compound. Some 

 states limit it by law to 50 per cent arsenious oxide and 3^ per 

 cent water-soluble arsenic. This insecticide costs from 25 cents 

 a pound up, depending upon the copper market and the avaricious- 

 ness of the dealer. Care has to be exercised in its use, otherwise 

 sprayed foliage is apt to be burned. It should never be used on 

 evergreens. 



A few simple tests are available to the farmer buying Paris 

 green. It should not be purchased at retail from open sacks or 

 other open containers where it is kept in bulk. It should be bright 

 green in color, not pale green. A small amount taken on a knife 

 blade, deposited on a piece of glass, and the glass then inclined and 

 gently tapped should leave on the glass a green streak ; if decidedly 

 pale green or whitish the Paris green is adulterated. 



Another test is to add a small amount (J^ teaspoonful) to a 

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