THE WAR ON INSECTS 291 



of any value in this direction. The petroleum mixt- 

 ures, indeed, usually kill the plants primarily and 

 the maggots consequentially. We derive some help 

 from carbolic acid emulsified with soap, so as to be 

 soluble in water. To make this, dissolve one pound of 

 hard soap shaved fine, in one gallon of boiling water, 

 add one pint of crude carbolic acid (50 per cent.), and 

 churn the whole into an emulsion with a force pump. 

 This emulsion is diluted for use with thirty times its 

 own bulk of water, and applied to the soil at the base of 

 infested plants. The mixture, to be effective, must 

 come into direct contact with the insects, hence the 

 earlier it is applied when cabbages and onions are 

 infested, the more effective it will be; there must be 

 enough material to penetrate down to the lowest point 

 reached by the maggots. On cabbages this may be 

 three or even four inches and may require half a pint of 

 material; on onions it would not be over an inch or 

 two, and would of course require much less. Wire- 

 worms and white grubs are also affected by this emul- 

 sion and driven away or killed. On growing foliage it 

 cannot be safely applied, and it is unsuitable for use 

 against maggots infesting radishes or beets. 



Carbolic acid is sometimes used to increase the 

 effectiveness of whale oil soap and an ounce of the 

 acid in a gallon of spray mixture does improve it to 

 some extent, but not enough to balance the extra cost 

 and labor of working it in. It has been added to air- 

 slacked lime for use as a repellent around melon and 

 other cucurbit vines to keep off the melon beetles. It 

 forms an ingredient in tree washes and preparations 

 intended to prevent the entrance of borers, and is 

 somewhat effective in this direction. But insects are 

 not often adversely affected by unpleasant odors unless 

 they are also directly poisonous. 



