- 18 - 
derris containing more than h percent of rotenone; the toxic value of 
Derris malaccensis (from to 2.7 percent rotenone) is "best expressed "by 
the following formula: Value. = rotenone content + 1/3 remainder of extract, 
Brevicoryne brassicae (L.), the cabbage aphid 
Heoton 197.5 S m - , plus an equal weight of soap in Uo imperial gal- 
lons of water, killed 100 percent. --Institute Physical and Chemical 
Research (162) in 1927. 
Davidson (6j, SU) in 1930 reported the following results: 
Concentration of s"pray 
Percentage of aphids hilled "by spraying with 
Rotenone : Racemic : Tephrosin : Toxicarol 
: deguelin : : 
1:500 - - 
1:5,000 - 
1:10,000 - 
1:20,000 - 
1:30,000 - 
1:100,000 
1:200.000 
100 
97.^ 
.9^-0 

• -The cabbage aphid was Used as a tost insect by Davidson and Jones 
(65) in I03I in studying the loss of toxicity suffered "by rotenone in 
certain solvents and in aqueous suspension. Rotenone at 1:10,000 killed 
98.5 percent of this species. 
Shepard ( 2^-1 ) in 1931 referred to unpublished' work by Davidson, 
who found that individual tests on the cahhage aphid' with rotenone suspen- 
sions at 1:100,000, but treated in different ways, resulted in 89. 0, Ug.U, 
6U.0, 22. U, and U6.5-percent mortality a.t the end of 1- day, but at the end 
of k days the same experiments, respectively, gave 95-6, 88.1, 95«5, 70.0, 
and 90.7-percent mortality. These data show the desirability of following 
the course of poisoning until the action is complete. 
Hamilton and G-emmell (37) i n 193^ reported that pyrethrum dust and 
a mixture of derris and pyrethrum were effective in laboratory tests 
against the cahbage aphid, while derris (1-percent rotenone) was less so. 
G-insDUrg and C-ranett (12U) in 1935 reported that several hundred 
young caDhage plants infested with the cahbage aphid were -sprayed thor- 
oughly on both surfaces of the leaf with a commercial -acetone extract of 
derris at a. concentration of 0.5 piht per 100 gallons of water plus -0.25 
percent of soap. Approximately 90 _ to 100- percent kill was noted 2 days 
later. Houghton and Byrne in 1935 stated in a letter to the chief of the 
Bureau of Entomology and Plant Quarantine that they failed to control the 
cabbage aphid with a dust containing 2.92-percent of ether .extractives 
but no rotenone. Howard ct al. ( 15^0 in 1935 reported dcrris to he less 
effective than... nicotine for control of the cahhagc aphid. Huckett and 
