PARIS GREEN. 33 1 



article to gain the desired end in spraying work. Lead arsenate 



can be used only in liquid form to be sprayed upon the foliage, 



and the usual formula is as follows : 



Lead arsenate - 3 lbs. 



Water 50 gallons. 



For sawfly larvae and some other insects that are easy to kill, 

 one pound in fifty gallons may suffice, and in spraying to kill 

 gypsy caterpillars five pounds in fifty gallons are the proportions 

 considered the most effective. In spraying for elm leaf beetle 

 larvae the poison should be directed against the under sides of 

 the leaves. The amount of lead arsenate may be increased greatly 

 without danger of injuring the foliage, and lime should not be 

 added. Lead arsenate can be used in connection with Bordeaux 

 mixture, though it is thought to be slightly less effective as an 

 insecticide when used in this way.* 



FORMULA FOR PARIS GREEN. 



Paris green is put up in powder form and can be applied either 

 dry or as a liquid. On account of the soluble acid which it con- 

 tains (see page 328 of this report) there is always danger of 

 "burning" the foliage unless some alkali is used with the poison. 

 For this purpose lime is Usually recommended, and the adhesive- 

 ness of the mixture is greatly improved by the lime. About three 

 pounds of lime should be used for each pound of Paris green. 

 If to be applied dry in a duster or powder gun, Paris green should 

 be mixed thoroughly with air-slaked lime or land plaster in the 

 following proportions : 



Piris green i pound. 



Air-slaked lime_ 100 pounds. 



For use as a spray Paris green may be prepared as follows : 



Paris green i pound. 



Fresh quicklime 3 pounds. 



Water ,- _ 100 gallons. 



In most orchards and potato fields Paris green is used in con- 

 nection with Bordeaux mixture, and as this contains an excess of 

 lime, no more lime is added. 



* Tests made at this Station show that the presence of the Bordeaux 

 mixture renders the lead arsenate perfectly insoluble. This perhaps may 

 account for its lessened poisonous effect on insects. 



