ARSENATE OF LEAD 67 



lead is a compound of arsenic, but is a less violent poison than Paris 

 green. The standard requirements for the paste call for at least 12 1 

 per cent arsenic oxid, not over f per cent soluble arsenic, and not 

 over 50 per cent water. 



To apply as a spray, the paste may be mixed with water, with Bor- 

 deaux mixture, or with lime-sulphur solution. In either case the 

 strength to employ is from 3 to 10 pounds of the paste in 50 

 gallons of water, or of Bordeaux mixture, or of lime-sulphur solution. 



If the dry lead arsenate is used in making up a spray, it is advan- 

 tageous to employ the finely powdered form made by the " electro " 

 process. The proportions will be from 1 to 4 pounds of the powder to 

 50 gallons. 



Either the paste or the powder should first be mixed with a little 

 water, so as to get it into a thin paste. It is entirely unnecessary to 

 add lime. 



Owing to the fact that arsenate of lead is not as violent a poison as 

 Paris green, it is necessary to use heavier doses for larger or resistant 

 insects, as indicated in the formula given above. 



Powdered arsenate of lead, applied dry, is developing a special field 

 of usefulness and promises to become a valuable form of insecticide 

 application. Paris green has been used in this way for many years, 

 especiall}^ on some truck and field crops in the South ; but it is rather 

 hkely to burn the foliage and is easily washed off by rains. Powdered 

 lead arsenate, especially the amorphous form made by the so-called 

 '' electro " process, rarely will burn the plants, and if apphed after a 

 shower or when the dew is on the leaves, it sticks tightly. 



On most truck crops or field crops it has important advantages over 

 liquid applications. The apparatus for applying it is light and inex- 

 pensive ; large areas can be covered easily and rapidly ; the need of 

 drawing a hea\y cart through the field is obviated ; and if a good pow- 

 der gun is used, the material can be forced in large quantities into the 

 places where it will do the most good. It is not suitable for orchard 

 work in general, or for work of such character as vineyard spraying. 



Advantages of lead arsenate are the facts that it will not usually 

 burn foliage, that it stays in suspension in the spray mixture fairly 



