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AN ECONOMIC ENTOMOLOGY. 



thus made, containing sixty-six per cent, of kerosene, will remain 

 unchanged for some time, and may be mixed with water to any ex- 

 tent. Soft water must be used for best results, and with very hard 

 water a real emulsion cannot be obtained at all without the addi- 

 tion of borax sufficient to soften it. Diluted from nine to twelve 

 times, this emulsion is very effective against plant-lice, many scale 

 insects, and such others as yield to contact insecticides in general. 

 Plants vary in their resistance to this material, not only absolutely 

 but relatively, under different climatic conditions. Diluted nine 

 times, few insects resist its effects, and only the hardier plants can 

 be safely treated ; diluted fifteen times, only the green plant-lice 

 are affected, while some foliage shows material injury. Where 

 plants do not readily stand a dilution of twelve times it is better 

 not to use the emulsion at all. For winter use, the emulsion is 

 useless as against dormant scales, and more injurious to trees than 

 the undiluted oil. 



In a mechanical mixture, applied with emulsion pumps, much 

 larger percentages of kerosene may be safely used, and as a 

 winter application, twenty to twenty-five per cent, of oil, is quite 

 effective against dormant scales when thoroughly applied. 



Another method of mixing oil and water is by using one of the 

 prepared finely ground limes or the very fine dry hydrate as fol- 

 lows : Pour the kerosene into a barrel, and for each gallon stir in 

 four pounds of lime, keeping the mixture in continuous motion un- 

 til it forms a thin, sloppy mass. In case a little k erosene separates 

 add more lime to absorb it. To this add water in quantity equal 

 to the kerosene, stir vigorously to get it well mixed, then add as 

 much more water as is needed to get the desired percentage, 

 and pump the mixture back into itself until a thorough emulsion 

 is secured. It is then a smooth mixture, which flows freely 

 through any nozzle, provided it is well agitated and no foreign 

 matter gets in. 



This kerosene lime, or K-L. reduced so that it contains twenty 

 to twenty-five per cent, kerosene, has been effectively used as a 

 winter wash against dormant scales, and it is safe if reasonably 

 used. As a summer wash, ten per cent, may be safely used on 

 most foliage. The lime here takes the place of soap as emulsify- 

 ing agent, but adds nothing to the effect against the insect nor 

 danger to the tree. Crude oil cannot be used in this way because 

 it forms clots. 



