l! I 

 QUASSIIN AS A CONTACT INSECTICIDE. ' 



Table II. — Results of experiments with quassiin as a contact insecticide — Continued. 

 SERIES NO. 3. WITH SOAP BARK ON PRUNE APHIS IN FIELD. 



Formula. 



Number of 

 aphides 

 sprayed. 



Per cent of 

 aphides 

 killed. 



0.4 grams to 2,000 cc. 

 0.4 grams to 1,800 ec. 



1,923 

 721 



97.5 

 99.2 



CHECK SERIES. 



"Whale-oil soap, 3 pounds to 100 gallons 



Soap bark, 2 pounds to 100 gallons 



Nicotine sulphate, 0.4 grams to 2,000 cc, with soap bark, 2 pounds to 100 gallons. 



1 These were the largest percentages obtained for the check materials. 



2 In field. 



From the foregoing table it will be readily seen that quassiin used 

 at the rate of 0.4 grams to 2,000 cubic centimeters, or 6J ounces of 

 40 per cent solution to 100 gallons, was almost as effective against the 

 hop aphis and the prune aphis as nicotine sulphate, 0.4 grams to 

 2,000 cubic centimeters, or 6 -J ounces to 100 gallons. The difference 

 is approximately 3 per cent, while quassiin, 0.4 grams to 1,000 cubic 

 centimeters, is fully as effective. 



The writer has not so far tested this material upon insects other 

 than those mentioned, but believes that it will prove effective else- 

 where if used in proportions corresponding to the amounts of nicotine 

 sulphate that are known to be effective. 



CONCLUSION. 



Picrasma excelsa Swz. (quassia wood) is a native of Jamaica, and, 

 according to data obtained, is available in considerable quantities. 



The percentage of quassiin in the quassia wood varies somewhat, 

 and does not appear to be definitely known. Supposing it to be 0.75 

 per cent, as given by one author, to use the quassiin at an effective 

 rate of 0.4 grams to 2,000 cubic centimeters, it would take only 1^ 

 pounds of the chips to 100 gallons of spray. To be on the safe side, 

 double the amount of chips calculated to be necessary, and we have 

 the following formula 1 and cost per 100 gallons of spray: 



Quassia chips, 0.75 per cent quassiin, 3 pounds, at $0.04 $0. 1 2 



Whale-oil soap, 3 pounds, at $0.04 12 



Total cost of materials per 100 gallons 24 



Quassiin can be readily extracted from quassia wood, Picrasma 

 excelsa Swz., in a comparatively pure form. (See p. 3.) It probably 

 could be more cheaply extracted in an impure water-soluble form by 

 using sodium carbonate solution. The percentage of quassiin could 

 be determined and the material evaporated until a standardized solu- 

 tion was made. Such a material could be diluted and used with 



1 This formula corresponds very closely to formula No. 1, page 2. 



