502 Journal of Agricultural Research voi. x. no. lo 



5.33 ounces of quassia chips with 2 quarts of water; 92 per cent of these 

 aphids died. Other branches of prune trees were sprayed with a solution 

 prepared in the proportion of 7 pounds of quassia chips to 250 gallons 

 of water; 96 per cent of these aphids were killed. Parker ascertained 

 that variously concocted formulas consisting of quassia extract and soap 

 solution are effective upon the hop aphis {Phorodon humuli Schr.) in 

 the field. He believes that the solution kills only by coming in contact 

 with the insects. The same author (33, p. 6), in the laboratory and in the 

 field sprayed hop aphids and prune aphids with three different formulas 

 in the proportion of ingredients as follows: (i) 0.4 gm. of quassiin to 

 2,000 c. c. of water with whale-oil soap; (2) 0.4 gm. of quassiin to 2,000 

 c. c. of water with soap bark; and (3) 0.4 gm. of nicotine sulphate to 

 2,000 c, c. of water with soap bark. He concluded that the formulas 

 containing quassiin were almost as effective as that containing nicotine 

 sulphate. He did not test the effects of the quassiin solution upon other 

 insects, but believes that it will prove effective elsewhere if used in pro- 

 portions corresponding to the amounts of nicotine sulphate that are 

 known to be effective. 



METHODS OF PREPARATION AND EFFECTIVENESS OF QUASSIA 



EXTRACTS 1 



An investigation of the efifectiveness of a substance as an insecticide 

 may be divided, as a rule, into two distinct phases: (i) The preparation 

 and preliminary testing in the laboratory of various extracts obtained 

 from the substance; and (2) the testing under outside or field conditions 

 of those solutions containing the extracts that have proved efficient in 

 the laboratory. 



I. — METHODS OF EXTRACTING QUASSIA CHIPS 



The bitter principle, quassiin, which is considered to be the active 

 constituent in quassia sprays, is claimed to be only slightly soluble in 

 watdr. It is important, therefore, to know just what method of ex- 

 traction is likely to insure the greatest quantity of this constituent. 

 A review of the literature reveals a wide difference in the results obtained 

 in extracting quassiin from the chips. The solubility of the quassiin, 

 as found by various investigators, appears to vary greatly, and, owing to 

 the confusion existing with respect to the practical methods of extracting 

 this substance, it seems advisable to include in the present investigation 

 some experiments to determine the value of the various methods. 



(a) Quantities of Extract Removed by Successive Extraction 



On the market, quassia chips vary greatly in size. A bag of this 

 material is likely to contain pieces varying in size from several inches in 

 length to very small fragments and sawdust. Since even the average- 

 sized chips are quite large, it was thought probable that they could be 



1 The word " extract" throughout this paper means the soUd material removed by a solvent. 



