INSECT ENEMIES AND DISEASES 
89 
with a direct nozzle to churn or agitate violently for 5 or 
7 0 minutes, or until the mixture is of the consistency 
of thick cream. If thoroughly emulsified the oil will 
not separate and the stock solution may be kept al- 
most indefinitely. Dilutions, ranging from 10 to 20 parts 
of water, with one of the stock solution, are used for 
various sucking insects. It is essential, of course, that 
the emulsioni come in contact with the enemy. This is 
not always easy to accomplish, especially when the in- 
sects are on the undersides of the leaves. 
133. Carbolic acid emulsion. — As a contact poison and 
a repellent carbolic acid emulsion is valuable in combat- 
ing onion maggots in small gardens. It is made in the 
same manner as kerosene emulsion (132), by using Y\ 
pound of soap, 1 gallon of water and % pint of crude 
carbolic acid. 
134. Tobacco is used in various forms. For dusting 
and spraying, tobacco in recent years has largely re- 
placed kerosene emulsion as a contact insecticide. To- 
bacco decoctions may be made by steeping the stems in 
water, but the commercial brands are in easy form to 
use and are more satisfactory. Tobacco stems also act 
as a repellent for lice and tobacco dust repels certain 
chewing insects, as the cucumber beetle. 
135. Soaps. — Whale-oil soap, 1 pound dissolved in 5 to 
7 gallons of water, makes a useful insecticide to control 
aphides and other minute insects. Hard and soft soaps 
may be substituted, but whale-oil soap makes a more 
effective spray. 
136. Miscellaneous insecticides. — Numerous other ma- 
terials are sometimes used in arresting the ravages of 
injurious insects, as calcium arsenate, sodium arsenite, 
zinc arsenite, and so forth. Lime, ashes, bordeaux mix- 
ture, land plaster or gypsum, and sulphur may be classed 
among insect repellents. A formalin solution is valu- 
able in treating seed potatoes both for the common scab 
