CHAPTER VIII 

 CONTACT INSECTICIDES 



For insects which do not feed upon solid food, stomach poisons are 

 useless, and sprays which come in contact with, and kill them in one or 

 another of the ways already indicated, must be used. This is unfortunate 

 for it means the most thorough kind of work if all the insects are to be 

 reached by the spray. It is among such insects too, that the greatest 

 difficulties in accomplishing this, occur. Some, though large enough to be 

 almost certainly reached by the spray have a particularly thick outer 

 shell: others are exceedingly small and thus can find protection under 

 buds, in crevices of the bark and in other places where the spray may not 

 reach them: still others form protective coverings (scales) over them- 

 selves, which fit tightly to the objects they may be on, so that a successful 

 spray must be very strong and penetrating: and finally, many of the 

 smallest and also of the scale-protected insects have marvelous powers of 

 increase, so that if even a single individual escapes treatment, a few 

 days or a week or two will find the plant again swarming with these 

 insects. 



Every insect therefore, which can be killed by a stomach poison is 

 best controlled by such materials. For the others, oils, soaps, nicotine, 

 sulfur compounds and a few other substances of minor importance serve 

 as contact insecticides. 



Considering the oils first, there are several which are of use. Among 

 mineral oils, crude petroleum and kerosene are destructive to insect life 

 but so dangerous to plants when of full strength, that some method of 

 dilution becomes necessary. 



Kerosene Emulsion: standard formula: 



Common laundry soap ^2 lb. 



Soft water 1 gal. 



Kerosene 2 gal. 



Dissolve the soap in the water (best by shaving it into hot water) : 

 then add the kerosene and with a small hand spray pump having a fine 

 nozzle, draw the mixture into the pump and out through the nozzle back 

 into the dish from which it was drawn. In a few minutes it should 

 become creamy and then begin to thicken. When it has become so 

 thick as to go hard through the pump, this process has been completed, 

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