210 The Principles of Vegetable- Gardening 



known to be so for many years. It has not come into general 

 use, however, because there has not been any device which would 

 thoroughly and accurately emulsify them. Within the last two 

 or three years, however, pumps have been invented which mix 

 and emulsify the kerosene and water in different proportions. 

 Some of these pumps are now sufficiently perfected to be recom- 

 mended with confidence. It is probable that within the next 

 few years these machines will be still further perfected, and the 

 kerosene and soap emulsion will then pass away. The kerosene 

 and water emulsion is cleaner, much more easily applied, and more 

 easy to make than the kerosene and soap emulsion. It has been 

 found that when the water and oil are thoroughly emulsified the 

 foliage will endure without injury an emulsion which contains 

 one -fourth or one -fifth of kerosene; and this strength is fatal 

 even to the San Jose scale. It is always best, however, when 

 applying the kerosene and water emulsions, to make the appli- 

 cation on a sunny day, so that the kerosene quickly evaporates. 

 Some plants are not injured by pure kerosene applied when 

 the sun is shining. Recent experiments and practice have 

 shown that an emulsion of water and crude petroleum makes 

 a very efficient insecticide ; but the grades of crude petro- 

 leum vary so much that it seems to be difficult to give gen- 

 eral advice. The grower should secure the latest bulletins on 

 the subject, as it is expected that considerable progress will be 

 made in this direction within the next few years. 



Whale-oil soap. — An old-time remedy for scale insects and 

 plant-lice is whale-oil soap. This is a very disagreeable com- 

 pound to dissolve and handle, however, and it is gradually giving 

 way to the kerosene emulsion, although it is a very efficient 

 insecticide. It is customary to dissolve one pound of whale-oil 

 soap in four or five gallons of water. One should experiment on 

 a few plants, if he is using a denser strength, before he applies 

 it on very large areas. Some tender plants are injured by the . 

 formula given above. 



Tobacco dust is a standard insecticide and repellent for some 

 insects. The striped cucumber and melon beetle is usually 

 driven away if the plants are thoroughly dusted with tobacco 



