108 



This substance is cheaper than arsenate of lead, but has 

 not been used long enough so that one is always sure of the 

 results which will be obtained. At the present time it seems 

 to be a promising insecticide, provided care is taken in mixing 

 to add lime enough to prevent burning the leaves. 



Contact Insecticides. 



Nicotine Sulfate, Ifi Per Cent. — This material is on sale 

 under various trade names selected by different manufac- 

 turers. It is rather expensive, but is so much diluted for use 

 that a little of it goes a long way as a spray. 



One part of the nicotine sulfate is usually mixed with about 

 800 parts of water. For a barrel pump, which holds about 

 50 gallons, the proportions are — 



Nicotine sulfate, 40 per cent (pint), . ^ 



Soap (pounds), . 2 to 3 



Water (gallons), 50 



Sometimes it can be used stronger than this for particu- 

 larly resistant insects, and in a few cases 1 part in 1,000 parts 

 of water (three-eighths of a pint in 50 gallons of water) is 

 strong enough, but 1 in 800 is the standard dilution. 



This is the best contact insecticide for plant lice, crawling 

 young of scale insects, etc., but if it cannot be obtained, kero- 

 sene emulsion, though not quite as effective, and troublesome 

 to prepare, may be used instead. 



Kerosene Emulsion. — This is prepared as follows: — 



Common laundry soap (pound), | 



Soft water (gallon), 1 



Kerosene (gallons), 2 



Dissolve the soap in the water (most quickly done by heat- 

 ing the water), remove from the fire, and add the kerosene. 

 Now, with a small hand spray pump and fine nozzle, spray 

 this mixture out of the pail or whatever it is in back into the 

 pail again through the pump, thus thoroughly mixing or 

 "churning" the materials. If this is properly done the mix- 

 ture should soon become milky, then gradually thicken until 

 it goes hard through the pump. This thickened material is 



