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Insecticides. 



Lead Arsenate. — Leaf-feeding insects of all kinds are usually best 

 controlled by poison sprays. Lead arsenate is the best of these for shade- 

 tree purposes; its initial cost is somewhat higher, but it adheres to the 

 foliage longer, and does not often burn the leaves when used at the ordinary 

 strength. It is usually sold in the form of a paste, and should be worked 

 up in a small amount of water before being diluted. For general spraying 

 against leaf-feeding insects, two pounds are mixed in 40 gallons of water; 

 but for bad infestations of canker-worms, forest tent caterpillars, and 

 certain others, especially when the caterpillars are more than one-half 

 grown, three or four pounds to the barrel of water should be employed. 



Lead arsenate is also used in the form of a powder. One pound of 

 the powder will do the work of about two pounds of the paste. 



Paris green is used at the rate of four ounces mixed in 40 gallons 

 of water for general spraying against leaf-feeding insects. When a stronger 

 mixture is required the poison may be increased to five ounces in 40 gallons. 

 There must always be added twice as much freshly slacked lime as Paris 

 green to prevent burning the foliage and the spray mixture must be kept 

 well stirred while spraying is in operation. 



Paris green 4-5 oz. 



Fresh lime ^-1 lb. 



Water 40 gallons. 



Kerosene emulsion. — Sucking insects such as plant lice and scale 

 insects are controlled by spraying the infested foliage with contact insecti- 

 cides, which must wet the insects in order to affect them. Kerosene 

 emulsion is generally used for this purpose. 



One-half pound of hard soap is shaved fine into one gallon of hot 

 water and stirred until dissolved. Two gallons of kerosene (coal oil) 

 are then added and the mixture immediately churned violently until a 

 thick creamy emulsion is produced. This churning is best done with a 

 bucket pump, putting the nozzle back into the bucket. The stock emul- 

 sion which is obtained when the mixture is properly made will keep for 

 months if covered from the air. For use on plant foliage it must be diluted 

 with water at the rate of one part of the stock solution well mixed in from 

 9 to 12 parts of soft water. 



