INSECTICIDES, PREVENTIVES, AND MACHINERY. 445 



sects with a fine coating of soap, which, in drying, closes up the 

 breathing pores, resulting in their death. It is thus that all 

 soaps act when used against plant-lice, larvae, or adult insects, 

 and it is readily seen that extreme thoroughness of application is 

 desirable. 



After trying a large proportion of the soaps on the market, I 

 have found nothing more effective for general use than good 

 whale-oil soap : the term "whale oil" including any kind of fish 

 oil that can be obtained cheap. The soap may be made by the 

 farmer himself, according to the formulas given on every package 

 of lye ; but, practically, the material is sold so cheaply that, un- 

 less labor counts for nothing, it is as economical to buy as it is to 

 make it. Whale-oil soap contains a considerable amount of 

 caustic, and where a very thick suds is applied, we have not 

 only the effect of the oil, but the prolonged effect of the caustic 

 contained in it. It is, therefore, especially useful for destroying 

 scale insects, against which caustics alone exercise a satisfactory 

 effect. In whale-oil soap the caustic softens or lifts the scales, 

 while the oil in the soap chokes the insect to death. To kill 

 scales on trees it should be applied during the winter, when the 

 vegetation is dormant, at the rate of two pounds in one gallon 

 of water. To destroy plant-lice and most other insects feeding 

 upon leaves, an extreme application is one pound in four gallons 

 of water, which is as much as most plants will safely stand, and 

 which is also effective against most of the insects upon which it 

 can be used. Most plant-Hce yield readily to one pound in six 

 gallons of water. In applying this material, thoroughness is es- 

 sential, and it is the disregard of this necessary feature that often 

 leads to failure. 



It sometimes happens that a really good fish-oil soap is not 

 obtainable at a moderate price, and where it is desirable that a 

 satisfactory effect be obtained against resistant scales like the 

 San Jose, the following formula will make an effective material : 



Concentrated lye lYz pounds. 



Water 8 gallons. 



Fish oil I gallon. 



Dissolve the lye in boiling water, and to the boiling solution 

 add the oil ; continue to boil for two and one-half hours, and then 



