PLANTS INSECTICIDAL 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 
p- 7 -) . . . 
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 larvae, 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 
Derris : 
1/3+4+100 95 
Pyrethrum : 
1+4+100 90 
Using the commercial products, the following percentages of 
aphids were killed : 
Derris: Per 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 (Macrosiphum ambro- 
siae Thos.), with some of the preceding products: 
Derris : Per cent 
1/1,000 100 
40 per cent nicotine sulphate : 
1/1,200 100 
Pyrethrum : 
1/1,000 95 
■" Cube :" 
1/3+4+100 100 
