PLANTS ISTSECnCIDAL, PROPERTIES. 13 



studies on derris (61) the resin was found to be the toxic principle. 

 The filtrate and cold-water extract were practically ineffective. (See 



Extracts of " cube" derris, and pyrethrum, and nicotine sulphate 

 used in field experiments. — Four rows of potatoes, badly infested 

 with potato beetles, and one large rose bush, badly infested with 

 rose aphids, were sprayed with a commercial extract of derris 

 (1/400) in soap solution (4/100). Another four rows of potatoes 

 and another rose bush, similarly infested, were sprayed with a com- 

 mercial soapy extract of pyrethrum (1/400) in soap solution (4/100) , 

 fish-oil soap being used in all these tests. Both preparations were 

 found efficient against the potato-beetle larvse, but had practically 

 no effect on the adult potato beetles and were inefficient against the 

 rose aphids. 



In July and August, 1922, the following experiments were per- 

 formed on aphids at Tallulah, La., by mixing various dilutions of 

 the insecticides with soap solution (4/100), laundry soap being used. 

 Small portions of rows of cotton plants, each 100 feet long and badly 

 infested with the cotton aphis (Aphis gossypii Glover), were sprayed 

 with alcoholic extracts of " cube," derris, and pyrethrum (prepared 

 in the laboratory), with commercial extracts of derris and pyre- 

 thrum, and with 40 per cent nicotine sulphate. 



Using the laboratory products, the following percentages of 

 aphids were killed : 



" Cube :" Per cent. 



1/2+4+100 99 



1/3+4+100 98 



1/4+4+100 95 



D'erris : 



1/3+4+100 95 



Pyrethrum : 



1+4+100 90 



Using the commercial products, the following percentages of 

 aphids were killed : 



Derris: p er cent 



1/2,000 95 



1/1,600 99 



1/1,000 99 



40 per cent nicotine sulphate : 



1/1,600 95 



1/1,200 96 



1/800 99 



Pyrethrum : 



1/1,000 95 



The following percentages were obtained by spraying many large 

 weeds heavily infested with large red aphids (Macrosiphvm ambro- 

 siae Thos.), with some of the preceding products : 



Derris: Per cent. 



1/1,600 100 



40 per cent nicotine sulphate : 



1/1,200 100 



Pyrethrum : 



1/1,000 95 



M Cube :" 



1/3+4+100 100 



