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Tischler ( 415 ) in 1935 studied the mechanism of how derris kills in- 
sects. Studies on the heart rates of various insects (including diamond- 
back cabbage worm) showed that the rate of pulsation was markedly de- 
creased before the insects exhibited incoordinated movements. Other tests 
made with insects including this species led to the conclusion that derris 
inhibits oxygen utilization by the tissues and that its detrimental effects 
are general rather than specific to any organ. 
Hervey, Huckett, and Glasgow (189) in 1935 recommended a dust contain- 
ing 0,5 percent of rotenone, made by diluting derris or cube with talc or 
clay and used. at the rate of 20 to 35 pounds per acre for the cor.trrl 
larvae of this species. A spray consisting of 4 pounds of derris povrcler 
(4 percent rotenone) plus 4 pounds of skim-milk powder per 100 gallons of 
water may also be used. 
Houghton and Byrne, in a letter to the Chief of the 3ureau of Ento- 
mology and Plant Quarantine of the United States Department of Agriculture, 
in 1935 wrote as follows concerning the use of derris as an insecticide 
in Australia: 
We have been getting very good control of cabbage moth with der- 
ris dust containing no rotenone whatsoever, but with a total of ether 
extractives in the finished dust of 2.92 percent. 
Howard, in a typewritten report to the Division of Truck Crop and 
Garden Insect Investigations of the bureau, in 1935 stated that derris 
root mixed with talc, infusorial earth, or tobacco dust so as to contain 
from 0.5 to 0.75 percent of rotenone and used at intervals of 7 to 10 
days at dosages of 25 to 30 pounds per acre per application was found to 
be fairly effective against the diamondback caterpillar. 
Howard, I'lason,and Davidson ( 197 ) in 1935 reported that derris dust 
was fairly effective. 
This species is more resistant than Fieris rapae to rotenone dust but 
may be satisfactorily held in check if the applications are not delayed 
too long. — Hov/ard and Fason ( 196 ) in 1937. 
-• Dusts containing 0.5 percent of rotenone are effective. — Huckett 
and Hervey (204) in 1935. 
• Morgan ( 283 ) in 1935 recommended dusting with lead arsenate plus an 
equal part of hydrated lime or kaolin until the cabbage begins 
then treating with 1 part of finely powdered derris root mixed with 9 
parts of talc. He said: 
In the writer* s experiments for the control of cabbage m 
with a dust consisting of 1 part of finely i -ed derris La 
9 parts of talc, 80 percent of the caterpillar: var- 
ious sizes up to the early stages of hearting were destroyed when 
the dust was applied at the rate of 1 pound to ' i 500 
plants. In 5 preliminary teste on plots each compr 1 ) cab 
