-110- 
L. A. Strong in a letter dated July 6, 1935, to Houghton and 
Byrne, Sydney, Australia, stated that in laboratory tests with the 
ground root of Tephrosia virginiana , which did not 6ontain any rote- 
none, approximately 36.6 percent of the quart er-gro^m larvae of the in- 
ported cabbage worm '"ere killed, as compared with e 55.0-perfient kill 
from the use of clay alone. Clay is one of the common diluents for 
rotenone-containing dusts. The total extractives of th.: Tcphrosia v:ere 
not known, but probably did not exceed 3 or 4 percent* .Amplications 
of Tephrosia dust containing 0,097, 0.067, 0.042, and 0.105 percent of 
rotcnone killed from 94 #4 to 98.3 percent of quart er-grov.-n lcr^ae. 
Those results indicated that the presence of rotenone in Tcphrosia does 
aid materially in increasing its. toxicity to quart er-gro^n larvae under 
laboratory conditions, 
F. L, Thomas ( 410) in 1935 recommended 1 part of derris (5 percent 
rotenone) mixed with 9 parts of finely ground conditioned sulfur for the 
control of cabbage worms, including this species. In 1936 Mr. Thomas 
(411 ) reported that in Texas derris-sulfur dust (0.5 percent rotenone) 
gave good results, ' 
VJhite (480 ) in 1935 recommended derris dust (0.5 to 1.0 percent 
rotenone) and derris spr^y (0.02 to 0.25 percent rotenone) for the con- 
trol of this insect. Later he ( 48l ) summarized the results obtained 
by th© Bureau of Entomology and Plant Quarantine at Chadbourn, N. C, 
Charleston, S. C., Baton Rouge, La., and Columbus, Ohio, with nonarseni- 
cal insecticides for the control of four species of cabbage worms in- 
cluding the imported cabbage worm, ^-s a general insecticide for the 
control of mixed populations, derris gave the best results and pyr cthrum 
came next in effectiveness. Based on the comparative officienoy, at 
economical strengths, of each of the insecticides tested against each of 
the principal species present, the sxporiments indicptod that rs a con- 
trol for the imported cabbage verm derris was more effective than pyrothrum, 
paris green, cryolite, or calcium arsenate, while pyrethrum wrs superior 
to the three last materials. i ;r hite in 1936 recommended derris dust con- 
taining 0,5 to 1.0 percent of rotenone for the control of cab' age -..'ems 
on cabbage and cauliflower at a dosage of 15 to 20 pounds per acre. It w 
found tb be especially important, however, td start the treatments early 
in the development of the cauliflower, while the plants were small, since 
it was not possible to obtain p good coverage of the insecticides ov 
the heavy foliage of nearly mature cauliflower plants. The experiments 
in 1934 on collards indicated that each of the three more common species 
of cabbage worms may be controlled satisfactorily with n derris-dust 
mixture containing 0.5 percent of rotenone. 'Vhite ( 482 ) i. 1937 r - 
ported that derris dust containing from 0.5 to 1.0 perc nt of rotenon6 
applied at the rate of 15 to 20 pounds per -ere, was the ri- 
al for use against thd imported cabbage worm, the cabbage looper, 
diamond-brck moth on cabbage. The rotenone content of derris roo*t r 08, 
and purchases should bo made on the basis of rotenone coni nt, total 
tractives, and degree o^ fineness. ■ '. , - ' con- 
taining 4 percent of rotenone should contain not 1©S6 than 14 p of 
total carbon-tetrachloride or - . . total 
extract (either by oarbon-tetrachloride or ether) she- approxi- 
mately three and one-half times the rot . root 
r der should be of such degree of I rfiont 
