THE CAMPHOR SCALE 13 



Formula 2. — When a power sprayer developing 300 to 400 pounds' 

 pressure is available, a soap emulsion can be more easily prepared 

 according to the following formula : 



Oil gallons— 10 



Water do 5 



Fish-oil soap pounds 3 



The ingredients should be combined unheated in the spray tank and 

 the mixture pumped at 300 to -100 pounds' pressure for 10 minutes. 

 On account of the increase in volume of the emulsion during prep- 

 aration, not more than half the capacity of the spray tank should be 

 made up at one time. 



The toxic effect of oil emulsions is due largely to the oil com- 

 ponent, the proportion of scales killed increasing with the quantity 

 uf oil left upon the sprayed plant. The quantity of oil deposited, 

 and hence the scale mortality, can be increased by decreasing the 

 quantity of soap used for emulsification. Emulsions made by the 

 second method have been used extensively in New Orleans, and 

 the proportion of soap given is the minimum that can be used 

 without danger of plant injury. It is best to test emulsions of this 

 type by diluting them in the spray tank and observing if there is 

 any surface accumulation of free oil when the agitator is running. 

 If so, the quantity of soap should be increased in order to avoid 

 applying a heavy concentration of oil to the trees as the last of the 

 spray liquid from the tank goes through the nozzle. Any emul- 

 sion of oil in water, emulsified with soap, tends to break down 

 when diluted with hard water, but the boiled emulsions made 

 by the first formula should be satisfactory for any fresh waters 

 encountered in southern Louisiana. The soap emulsions keep 

 better than those made with casein-lime spreader, and stock mix- 

 tures for the season's spraying can be prepared in advance. Such 

 mixtures, however, should always be well agitated before any is 

 withdrawn for dilution, so that the final sprays will be uniform in 

 quality. 



Formula 3. — Emulsions that are not affected by hard waters may 

 be prepared with certain nonsoap emulsifiers, such as casein-lime 

 spreader. An emulsion may be prepared as follows : 



Lubricating oil gallons— 8 



Water do 4 



Casein-lime pound 1 



The casein-lime should be dissolved in a small quantity of the water, 

 the remainder of the water then added, and the oil-water mixture 

 pumped back upon itself until emulsified. These emulsions do not 

 keep well and should be prepared only as needed for use. 



TYPE OF OIL TO BE USED 



Mineral oils of the cheaper lubricating type make the most satis- 

 factory sprays from the standpoints of cost of materials and toxicity 

 to the camphor scale. A number of physical and chemical charac- 

 teristics are listed by the manufacturers of such oils, but most of 

 these specifications indicate their value as lubricants and may have 

 little bearing upon their insecticidal value. Only volatility, viscos- 

 ity, and unsulphonatable residue will be considered here. 



