374 MANUAL OF VEGETABLE-GARDEN INSECTS 



work. If the sulfur vapor is condensed to the liquid form in 

 a cold receiver, roll sulfur is formed. Flour of sulfur is made 

 by grinding roll sulfur to a fine powder. 



In the form of a powder or dust, sulfur is especially valuable 

 against red-spider. For this purpose it is often diluted with 

 hydrated lime and may be applied mixed with water at the 

 rate of 1 pound in 3 gallons, in which a little soap has been 

 dissolved to help keep the sulfur in suspension. The sulfur 

 settles quickly and should be agitated constantly during spray- 

 ing. The sulfur will remain in suspension longer if first made 

 into a paste with water containing i of one per cent of glue. 



Emulsions. 



Emulsions are sprays in which oils are suspended in water 

 in the form of minute globules, a condition brought about by 

 the addition of soap. They form an important class of contact 

 insecticides useful particularly against plant-lice and other 

 soft-bodied insects. 



Kerosene emulsion is one of the oldest of contact insecticides. 

 It is prepared by the following formula : 



Soap i pound 



Water 1 gallon 



Kerosene 2 gallons 



Dissolve the soap in hot water; remove from the fire and 

 while still hot add the kerosene. Pump the liquid back into 

 itself for five or ten minutes or until it becomes a creamy mass. 

 If properly made the oil will not separate on cooling. 



For killing plant-lice on foliage, dilute with 10 to 15 parts 

 of water. The strength of oil emulsions is frequently indicated 

 by the percentage of oil in the diluted liquid : 



For a 10 per cent emulsion add 17 gal. water to 3 gal. stock emulsion. 

 For a 15 per cent emulsion add 10.^ gal. water to 3 gal. stock emulsion. 

 For a 20 per cent emulsion add 7 gal. water to 3 gal. stock emulsion. 

 For a 25 per cent emulsion add 5 gal. water to 3 gal. stock emulsion. 



