ig NEW YORK STATE MUSEUM 



usually advised. It is also well to employ an equal amount of recently 

 slaked lime (mix with considerable water and strain before adding) in order 

 to lessen the danger of burning the foliage. It is essential that either of 

 the above mixtures be kept well stirred in order to secure uniform results, 

 as the latter named poisons, in particular, sink rapidly to the bottom of the 

 tank. 



Formulas for contact insecticides. Kerosene emulsion is one of the 

 most important contact insecticides, that is, those- which must be actually 

 thrown on the insect in order to secure results. It may be prepared as fol- 

 lows : dissolve one half pound of hard soap in a gallon of boiling water 

 and while it is still hot add two gallons of kerosene, and emulsify either by 

 stirring rapidly or by repeatedly forcing it through a pump and fine nozzle. 

 A white, uniform creamy mass which does not break up into oil and water 

 should be obtained and this can then readily be diluted with water, the 

 usual amount being nine parts water to one of the emulsion. A sour milk 

 emulsion should be used in limestone regions, two gallons of kerosene to 

 one gallon of sour milk, emulsify as described above and dilute. The 

 10% mechanical kerosene emulsion can be used in a similar manner, pro- 

 vided the pump can be depended on to give reliable proportions, which is 

 not often the case. One pound of whale oil soap to four gallons of water 

 is the strongest that can be used safely on foliage and one pound to six gal- 

 lons is usually as effectual as the kerosene emulsion for similar purposes. 



The abov^ formulas are to be used on trees in foliage and can be 

 depended on to kill only the more tender insects. The abundance of cer- 

 tain scale insects in recent years has shown the need of something more 

 effective and what are known as winter washes have been devised. These 

 are more penetrating corrosive or alkaline substances which can be applied 

 with safety to trees only while they are dormant, and are therefore more fatal 

 to insect life. The whale oil soap solution, 2 pounds to a gallon, comes 

 under this head and it may be applied either in the fall or spring for 

 the destruction of certain scale insects. It has been used very success- 

 fully against the San Jose scale, Aspidiotus perniciosus Comst. 



