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- 
