18 



Among substances employed for this purpose coal oil 

 (kerosene), Persian insect powder (pyrethrum), buhach, 

 and white hellebore, are well known for their effective- 

 ness. A " resin compound, " more recently recognized 

 as useful, is now used successfully for scale insects on 

 orange trees, in the West, and is highly recommended 

 by some of our best authorities on the treatment of such 

 pests. The methods of preparing and using such insec- 

 ticides have been so frequently considered in Station re- 

 ports that it is not necessary to go into detail here. Those 

 especially interested in these matters will find a condensed 

 account of the insecticides and fungicicdes in common 

 use, in Circular No. 3, of this Experiment Station. As a 

 matter of convenience I will, however, give the formulae 

 for making the two preparations best calculated, by vir- 

 tue of their cheapness and effectiveness, for use on trees. 



Kerosene, or coal oil, is now everywhere applied to 

 plants as an emulsion, which may be prepared as follows : 

 Dissolve one-half pound of cheap soap in a gallon of hot 

 water, then while still hot add to this two gallons of ker- 

 osene, and finally pass the whole through a pump, re- 

 turning it with force to the vessel whence it is being 

 pumped up. In a few minutes it will assume the ap- 

 pearance of cream, and if the churning has been 

 thoroughly done it will retain this consistency and [ap- 

 pearance. It is in fact an emulsion, and in this condi- 

 tion the oil may be mixed with water in any proportion. 

 Herein consists its advantage over pure coal oil. It 

 maybe so diluted that it will do no injury to leaves, but 

 still retains all its properties as an insecticide. 



Mr. Koebele who has perhaps had as much experience 

 with the resin compound as any one, recommended a few 

 years ago the following formula for its preparation : 



Sal-soda, 3 lbs. 



Resin, 4 lbs. 



