17 



Crude petroleum emulsion. — Crude petroleum emulsion may be pre- 

 pared 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 kero- 

 sene emulsion, Init 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. 



Miscible oils. — Under the heading "Miscible oils" are to be desig- 

 nated several proprietary preparations which are essentially petro- 

 leum oils with the addition of a vegetable oil and an alkali, to secure 

 ready saponification with water. These come in concentrated solu- 

 tions and the spray is prepared by adding a specified amount of water. 

 In point of convenience they leave little to be desired. Miscible 

 oils are coming into increased use in place of kerosene or crude petro- 

 leum, either pure or in emulsions, and have a distinct usefulness as 

 winter spra3^s about the same as have the concentrated lime-sulphur 

 solutions. As has been indicated, the petroleum oils are at times the 

 cause of injury to twigs and fruit buds, and it is a question of judg- 

 ment whether, under conditions of severe scale infestation, the petro- 

 leum oils or the sulphur solutions should be used. The ])etroleum 

 oils, on the whole, are more effective and the danger of injury from 

 them is less to pome than to stone fruits. 



The practicability of making miscible oils at home has been inves- 

 tigated by Prof. C. L. Penny,'^ and he has shown it to be entirely 

 feasible, as detailed in the publications cited below. 



SOAP WASHES. 



Practically the only soap wash which has come into extended use 

 against the San Jose scale is that made from whale-oil soaj). This is 

 used mostly on dormant trees, the soap being employed at the rate 

 of 2 pounds to the gallon of water. A potash whale-oil soap is prefer- 

 able and should contain not more than 30 per cent of water. Soda 

 soaps, while perhaps cheaper, will be likely to solidify on cooling 

 when used at the strength above indicated, and are hence forced 

 througli the spray-pump nozzle with difficulty. For spraying trees 

 in foliage the soaj) should be used at tlie rate of 1 pound to 3 or 4 

 gallons of water, or somewhat weaker. 



SPRAYING APPARATUS. 



The washes as above described are applied by means of some form 

 of spray pump, the size and character depending upon the size of the 

 plants to be treated. For small plants, such as ornamentals, hedges, 

 etc., a bucket pump (fig. S) or knapsack pump (fig. 9) will be satis- 

 factory. The barrel form of puni]), however (fig. 10), will permit of 

 more thorough work and will be suitable for orchards of some size. 



<i Bui. 75, Del. Coll. Agr. Exp. Sta. (1906). 

 Bui. 85, Pa. State Coll. Agr. Exp. Sta. (1908). State College, Ta. 



