INSECTS INJURIOUS TO CITRUS FRUITS 619 



" Difficulties that may arise in making the boiled formula are: 

 (1) A lack of sufficient heat; (2) improper pumping; (3) an improper 

 emulsifier. In many tests the water and soap only were heated, 

 and failure to produce a perfect emulsion resulted in every instance. 

 On the other hand, when all the materials were heated together a 

 perfect emulsion was secured. The materials should be heated 

 until a slight foam or a few bubbles appear, but it is not necessary 

 to boil for any length of time. 



"Some growers have failed because they attempted to stir the 

 materials together with a stick, and others because they used a 

 rotary pump. Neither of these is satisfactory. 



<( The emulsifying agent is very important. There is "no doubt 

 that potash fish-oil soap is the most satisfactory of all soaps for 

 the making of any of these emulsions. When this material is 

 used the oil very seldom separates and the resulting emulsions 

 never become too thick to be poured or handled conveniently. 

 On the other hand, when hard soaps are used which are made 

 from caustic soda and fats containing large proportions of stearin 

 and small quantities of resin, the emulsions separate on cooling, 

 and will cause much trouble in mixing on the day after they are 

 made. If the emulsion made from any hard soap found on the 

 market is used on the same day that it is made no trouble will be 

 experienced. The 'cold-stirred' formula is difficult to make with 

 hard soaps. The writer has found it impossible to make emulsions 

 by using any of the soap powders, even if flour is used as a 

 stabilizer. 



" Before any spray material is applied to a tree it should be 

 tested to determine if it is a perfect emulsion. To do this, add 

 a small amount to some soft water; if no oil floats or no thick, 

 greasy scum forms, it is satisfactory. If free oil appears the 

 emulsion is imperfect and should not be used. Great care should 

 be used to stir the contents of the barrel thoroughly before any 

 test is made. 



"Just at present the boiled-emulsion formula is the one which 

 will appeal to the average citrus grower in Florida. It is, beyond 

 all question, the cheapest effective insecticide for white flies and 

 scale insects. 



"The oils used in the making of these formulas usually test 

 from 24 to 32 Baume and have a viscosity not less than 200. 



