22 



another. Then to determine how much to dilute each of these to get a strength of 

 1.035 divide the last three figures of the 1.300 and 1.380, respectively, by 35, and 

 this will give the total number of gallons which each gallon, respectively, will make. 

 Thus 300-^35=:8 20-35, or approximately 8%, and 280^35=8. This means that 

 each gallon of the strength of 1.300 must be diluted with water to 8% gals, to make 

 a strength of 1.035, and each gal. of the strength of 1.280 to 8 gals, to give the 

 same strength. 



Those who wish to use the old home-boiled lime-sulphur, an excellent but 

 troublesome spray to make and apply, should consult Bulletin 198, page 14. 



Formula for Kerosene Emulsion for Use on Scale. — A number of fruit- 

 growers in the districts where there are oil wells have asked for a formula by which 

 they could make use of crude petroleum against San Jose Scale. The following 

 formula is taken from Circular No. 124, Bureau of Entomology, Washington, D.C. : 



"Kerosene Emulsion {stock solution 66 per cent. oil). Kerosene emulsion is 

 made after the following formula : — 



Kerosene (coal oil, lamp oil) gallons 2 



Whale-oil soap or laundry soap (or 1 quart of soft soap) . . . .pound >4 

 Water gallon 1 



Dissolve the soap in boiling water, then remove vessel from the fire. Immed- 

 iately add the kerosene, and thoroughly agitate the mixture until a creamy solution 

 results. The stock emulsion may be more conveniently made by pouring the mix- 

 ture into the tank of a spray pump and pumping the liquid through the nozzle 

 back into the tank for some minutes. The stock solution, if well made, will keep 

 for some months, and is to be diluted before using. In order to make a 10 per cent, 

 spray (the strength for trees in foliage), add" to each one gallon of the stock solu- 

 tion about 5% gals, of water. For 20 and 25 per cent, emulsions (for use on dormant 

 trees and plants), use, respectively, about 2>^ gallons and 1% gallons of water for 

 each one gallon of stock emulsion. Agitate the mixture in all cases after adding 

 the water. The preparation of the emulsion will be simplified by the use of 

 naptha soap. No heat will be required, as the kerosene will combine readily with 

 the soap in water when thoroughly agitated. Of naphtha soap, however, double the 

 quantity given in the above formula will be required, and soft or rain water should 

 be used in making the emulsion. In regions where the water is " hard " this should 

 first be broken with a little caustic potash or soda, such as common lye, before use for 

 dilution, to prevent the soap from combining with the lime or magnesia present, thus 

 liberating some of the kerosene ; or rain water may be employed. 



Crude Petroleum Emulsion. Crude petroleum emulsion may be prepared in 

 identically the same way as described for kerosene emulsion, substituting crude 

 petroleum for kerosene. The same dilutions for winter and summer spraying should 

 be made as prescribed for kerosene emulsion, but it should be noted that for summer 

 treatments of trees in foliage the kerosene emulsion is preferable, as it is less likely 

 to cause injury. 



I have not myself tested these emulsions, but would advise that they should be 

 used only to supplement lime-sulphur in spring, especially on the outer branches 

 and twigs of large apple trees. It is not safe to drench trees with any oil wash, 

 particularly the trunks and large branches. Spraying should be stopped as soon 

 as it is seen that the part is well covered, and before it legins to run. It is also 

 safer to spray on a bright or windy day than in dark gloomy weather, because the 



