TREE INSECTS AND THEIR CONTROL 191 



Nicotine Sulphate. This is a liquid extract of tobacco, 

 which is effective against aphids, or plant lice, and other 

 soft-bodied insects. It may be bought under numerous 

 trade names. The strength varies with the different 

 preparations, and directions for proper dilution with water 

 are usually printed on the labels. The most used form 

 is the 40 per cent, nicotine sulphate, although any strength 

 may be used when properly diluted. The addition of 1 

 ounce of soap to each gallon of spray is useful in causing 

 the material to spread and stick. 



Fish-oil Soap. This material, also known as whale-oil 

 soap, is effective against aphids, scale insects and other 

 sap-suckers. For use in summer spraying, dissolve 1 

 pound of the soap in from 3 to 4 gallons of water. For use 

 against scale insects in winter, dissolve 2 pounds of the 

 soap in each gallon of water. The mixing should be done 

 over a fire and the spray used before the solution is cold, 

 as the mixture congeals upon cooling. Common laundry 

 soap may be used instead of the fish-oil soap. 



Poisoned Contact Sprays. For use against borers, 

 while they are still feeding in the bark, sodium arsenite 

 should be added to either kerosene emulsion or miscible 

 oil sprays. The addition of this poison makes what is 

 known as a poisoned contact spray, which penetrates 

 where ordinary water solutions would be ineffectual. 

 Sodium arsenite may be obtained at drug stores. When 

 diluting the kerosene emulsion or miscible oil for use, add 

 one ounce of sodium arsenite to each gallon of the water 

 employed for dilution, allowing the poison to dissolve 

 before making the final mixture. The poisoned contact 

 sprays are injurious to foliage and should be applied 

 with care. 



Carbon Disulphid. Carbon disulphid partakes of the 

 nature of contact remedies, but its use is along dif- 



