CONTROL OF THE HOP APHIS. 29 



THE USE OF QUASSIA. 



Various formulas for quassia spray are used in the field and were 



observed to be effective when properly prepared. Some of them are 



as follows: 



Formula No. 1. 



Cents. 



Quassia chips, 7 pounds, at 5^ cents per pound 37 



Whale-oil soap, 9 pounds, at 4^ cents per pound ( . . 40.5 



Water, 250 gallons. Total cost per 100 gallons 31 



Formula No. 2. 



Cents. 



Quassia chips, 8 pounds, at 5^ cents per pound 42 



Whale-oil soap, 6 pounds, at 4^ cents per pound 27 



Water, 100 gallons. Total cost per 100 gallons 69 



Formula No. 3. 



Cents. 



Quassia chips, 9 pounds, at b\ cents per pound 47. 2 



Whale-oil soap, 6 pounds, at 4^ cents per pound 27 



Water, 100 gallons. Total cost per 100 gallons 74. 2 



Formula No. 1 was used by Prof. W. T. Clarke in his work upon 

 the hop aphis at Watson ville, Cal., in 1902. It was also successfully 

 used by the writer in some field experiments at Santa Rosa, Cal. ; 

 during 1911. The other formulas are stronger and have also been 

 observed to be effective when properly prepared. 



PREPARATION. 



Many failures in control work, when quassia is used, are due to 

 faulty preparation of the material. Some growers only soak the chips 

 and use what soaks out. Others boil them without previous soak- 

 ing. The proper way to prepare quassia spray, based on Formula 

 No. 1, is as follows: 



Soak the chips 24 hours, then boil for 2 hours in 3 gallons of water. Add this 

 decoction to 247 gallons of water in which the soap has been dissolved. The whale- 

 oil soap is readily dissolved by boiling in a small amount of water. 



QUALITY OF QUASSIA. 



The quality of quassia may vary and the percentage of quassin 

 which can be extracted from the different grades of chips will not 

 be the same. For this reason the use of quassia chips is not so 

 certain in its results as a material containing a known amount of 

 insecticide. When the quassia chips are used, it is well to look 

 over sprayed areas three days after they are sprayed to be sure that 

 the spray has been effective. 



