Amj arsenite of knoirn composition may he applied in quanlity to furnish 

 metallic arsenic equal to that in an application of Paris green, trhereas any 

 arsenate of known composition may be applied to furnish metallic arsenic 

 equivalent in amount to that used in arsenate of lead. 



For most farm and orchard crops it is umnse to use anj^ arsenical 

 without protecting the plant against foliage injury. The addition of 

 milk of lime affords i)rotection against this arsenical injury. Four pounds 

 of high-grade quicklime (95 per cent CaO) are generally sufficient for 50 

 gallons (1 barrel) of spray. The lime should be slaked carefully, sieved, 

 diluted to nearly 50 gallons, and the arsenical added slowly, with thorough 

 agitation, immediately before application. 



II. Contact Poisons for Sucking Insects. 



Contact poisons mclude a large nmuber of diversified compounds (solid, 

 liquid and gaseous), and their effectiveness may depend upon more than 

 one property. The compound may act in any of the following ways: — 



1. Glue the insect down. 



2. Attack the body, dissolving fat and even muscle, precipitating proteids, etc. 



3. Act as a narcotic, paralyzant or anajsthetic. 



4. Asphyxiate the insect by closing the breathing pores (spiracles or trachea)), 

 •or, by saturating the body, prevent necessary aeration. 



These indicate some of the possibilities. These poisons are generally 

 ■soluble or emulsified products. They kill only by contact; hence liberal 

 and thorough application is necessary to insure effectiveness. The most 

 important contact poisons are (1) soaps, (2) sulfur sprays, (3) oil sprays, 

 and (4) nicotine. 



Composition and Properties of Contact Poisons. 

 {1) Soaps. 

 Whale-oil or fish-oil soaps are those most generally used in spraying, 

 although common laundry soap may also be used. There are also soap 

 preparations with rosin, making a so-called "soap sticker," and mixtures 

 of soap with nicotine, the effect of the nicotine being to make the whole 

 spray more effective against certain types of insects, and of the soap, to 

 volatihze the nicotine, and in this way increase the rapidity of its action. 

 These materials are not standardized. They may be purchased merely 

 as "soaps," and hence need not come under the provisions of the insecticide 

 act of 1910. The guaranty of analysis, if given, has but little significance. 



