INSECTICIDES 45 



most effectively by the use of a powder-gun, which consists 

 of a rotating fan which drives the poison from a reservoir through 

 a tube by which it may be directed to the desired point. The 

 powder-guns most commonly used are carried by a man, though 

 larger machines carried on a wagon are in use for orchard work. 

 Paris green is usually diluted with 10 to 20 parts of flour, ground 

 gypsum, or preferably air-slaked lime, though some prefer to 

 use it undiluted when machines are used which control the amount 

 of the application. Dusting should be done while the dew is 

 on the foliage in early morning, except on such plants as have a 

 rough or adhesive foliage. Paris green is frequently used as a 

 dust upon potatoes, cabbage and other garden crops, as well as 

 for dusting weeds and grass for grasshoppers, army worms, etc. 

 Powdered arsenate of lead has recently been shown to be an 

 effective remedy for the cotton boll weevil (see page 272), and 

 is used pure. Its use in dry form will doubtless be found more 

 practicable on other crops than has that of Paris green. 



5. Arsenite of lime is a home-made arsenical, very much cheaper 

 than those previously mentioned, and giving very satisfactoiy 

 results for certain purposes. It is not as adhesive as arsenate 

 of lead, and as it sometimes burns foliage has been largely dis- 

 carded for orchard spraying. It is, however, very satisfactory 

 for potatoes and other low-growing crops, especially when added 

 to Bordeaux mixture, which sticks it to the foliage, and it may be 

 used to good advantage for righting grasshoppers and leaf-eating 

 caterpillars when it is desired to poison considerable areas of 

 weeds or waste grass. The so-called Kedzie formula is the most 

 satisfactory, as the soda hastens the complete combination of 

 the arsenic, and the resulting solution is in a clear liquid form 

 which can be readily measured.* Take 1 pound of white arsenic 



* Arsenite of lime is often made by boiling 1 pound of lime with 2 pounds 

 of white arsenic in 1 gallon of water for thirty to forty-five minutes. This 

 ' results in a paste of arsenite of lime, which settles in the solution. One quart 

 of this mixture is used per barrel of water or Bordeaux mixture, but unless 

 the stock solution is always stirred equally well, the amount of poison in a 

 quart will be quite variable, with varying effectiveness; hence the clear 

 solution of arsenite of soda as in the above formula is preferable. 



