286 INSECTS 



kill every scale it touches, and it spreads so well that it 

 will get under every protection, into every crevice and 

 through every covering of plant hairs. Unfortunately 

 it goes further and, if carelessly used, is just as likely 

 to get through the outer bark into the bast, and to kill 

 the tree as well as the insect. Nevertheless the material 

 has been and is even yet quite extensively used, and is 

 the reliance of a large number of good fruit-growers. 

 I do not advise its general use, but mention it for the 

 benefit of those willing to try it. In the garden and 

 conservatory it has no place. 



Kerosene is a derivative from the crude petroleum, 

 with the lighter volatile oils, the vaseline and the par- 

 affine eliminated. It can be safely applied to trees 

 even when in full foliage, in a very fine spray, under 

 conditions which favor rapid evaporation. I have 

 frequently applied it with excellent effect late in summer 

 on very scaly trees, killing off most of the insects with- 

 out appreciable harm to the tree itself. Apple and 

 pear trees are most resistant to the mineral oils; peach 

 and other stone fruits are most susceptible. Citrus 

 trees stand kerosene very well under favorable condi- 

 tions; but on the whole this is another material which 

 needs a thorough appreciation of all the factors in- 

 volved to make it safe. As a winter application it is 

 not nearly so effective as crude oil because it evapo- 

 rates so much more completely, leaving nothing in the 

 way of a coating to continue its work; but that very 

 feature makes it safer to use. 



The good points of kerosene as an insecticide were 

 long ago recognized, and nearly thirty years ago methods 

 of emulsifying it with milk and afterward with soap 

 were worked out under the direction of Dr. C. V. Riley 

 then U. S. entomologist, by Mr. H. G. Hubbard. The 

 milk formula was soon abandoned; but the soap emul- 



