Materials and Formulas. 167 



and it may be that the insects are also more easily treated here. 

 But in California and in the South, the resin solutions are very 

 highly valued, as they appear to be more efficient than those 

 containing kerosene. 



Applications are made to dormant as well as to growing trees. 

 In the former case stronger mixtures are used with success, but 

 if used during summer, the same ones might cause much dam- 

 age. When selecting from the formulas given below, the nature 

 of the treatment must be kept in mind, to avoid injuring the 

 trees. It is advisable to use a covered iron kettle for boiling the 

 ingredients of the insecticides. 



Resin 20 pounds. 



Caustic soda (70 per cent) 5 " 



Fish-oil 2 pints. 



Water to make 100 gallons. 



The first three ingredients should be placed in a large kettle 

 and covered with four or five inches of water. Boil for one or 

 two hours, or until the liquid has a dark brown color resembling 

 coffee. 



The use of a 98 per cent granulated caustic soda shortens the 

 required time of boiling. In case this is used, its amount may 

 be reduced to 3 pounds, and 3 pounds of fish-oil should also 

 be added. Under such circumstances, these ingredients may be 

 boiled a moment with but 15 gallons of water and a stock solu- 

 tion thus obtained, which may be diluted at will. (The total 

 cost is about five and one-third cents per gallon.) These two 

 formulas are very extensively employed in the work of the United 

 States Department of Agriculture. 



When water is added to the solutions, it should be poured in 

 slowly and thoroughly mixed. Dilute as required, in green- 

 houses 1-3, or 1-4. For use in summer. 



Resin 40 pounds. 



Caustic soda (98 per cent) 10 " 



Potash 10 " 



Tallow 40 " 



Water to make 50 gallons. 



Dissolve the soda and the potash in about 10 gallons of hot 

 water. The resin and the tallow should be heated, and when 

 dissolved and thoroughly mixed, pour the two solutions into a 



