364 "INSECTS AFFECTING VEGETATION 



greatest fault. "To give better suspension in water, it should be re- 

 duced to such fineness by grinding that it will pass through a 100- 

 mesh sieve. Its high cost (varying from 20 to 40 cents a pound, fol- 

 lowing the market price of copper and arsenic) is further increased 

 by its being crystallized with acetic acid, making it a more brilliant 

 pigment, but giving it a coarse grain and rendering it a poorer in- 

 secticide. The standards of purity demanded by various States have 

 led most manufacturers to produce a very fair article, but if there is 

 any doubt of purity a sample should be submitted to the State Ex- 

 periment Station or to the United States Department of Agriculture 

 for analysis. 



Hellebore. The powdered roots of the white hellebore (Vera- 

 trum viride) are often recommended and used as an insecticide, par- 

 ticularly as a substitute for the arsenites. This substance is useful 

 when a few plants only are to be sprayed, as in yards and small gar- 

 dens, but is too expensive for large operations. It kills insects in the 

 same w r ay as the arsenicals, as an internal poison, and is less danger- 

 ous to man and the higher animals; but if a sufficient amount be 

 taken it will cause death. It is particularly effective against the 

 larvae of sawflies, such as the cherry slug, rose slug, currant worms, 

 and strawberry worms. It may be applied as a dry powder, prefer- 

 ably diluted with from 5 to 10 parts of flour, and dusted on the 

 plants through a muslin bag or with powder bellows. The applica- 

 tion should be made in the morning, when the plants are moist with 

 dew. Used as a wet application, it should be mixed with water in 

 the proportion of 1 ounce to the gallon of water and applied as a 

 spray. 



Arsenite of Lime. This is normally a home-made preparation, 

 and there is no reason for its not being employed wherever one is 

 willing to take the trouble to compound it carefully. Its prepara- 

 tion, described below, following substantially the Kedzie formula, is 

 simple enough: 



White arsenic pounds . . 1 



Crystal sal soda* do ... 4 



Water gallons . . 1 



Place the above ingredients in an iron vessel, which is to be 

 kept exclusively for this purpose, and boil for twenty minutes or 

 until dissolved. To 40 or 50 gallons of water a pint of this stock 

 solution and 3 to 4 pounds of freshly slaked lime are added. This 

 excess of lime not only takes up any free arsenic, but by its distribu- 

 tion on the foliage enables one to determine how well the spraying 

 has been done. This formula has been thoroughly tested and used 

 now for many years, and is fully as efficient as any other arsenical 

 and far cheaper. Chemically it is arsenite of lime. The soda is used 

 to hasten the process and to insure the combination of all the arsenic 

 with the lime. The greatest care should be exercised in preparing 

 the stock mixture, and afterwards it should be plainly labeled to pre- 

 vent its being mistaken for some other substance. The only objec- 



*Two pounds only of the anhydrous sal soda are necessary. 



