-105- 
r, Large larvae on cabbage were all killed by a dust consisting of 1 part 
/rotenone and 99 parts of diatoraaceous earth. — Davidson (90) in 1930* 
Davidson and Jones (91) in 1931 reported on the change in aqueous 
suspension. Rotenone in solution in pyridine, or in acetone to which 
tannic acid has been added, rapidly loses its insecticidal effective- 
ness. This loss in toxicity is accompanied by a decrease in optical 
activity and a progressive yellowing of the solution. Atmospheric oxi- 
dation of the rotenone appears to account for these changes. The yellow 
crystalline material resulting from the oxidation of rotenone in pyri- 
dine solution was tested on goldfish and insects and was found to be 
much less toxic than rotenone. In acetone or in alcohol rotenone de- 
composes very slowly. In aqueous suspensions made from fresh acetone 
and alcohol stock solutions rotenone loses toxicity upon standing. A 
suspension of rotenone in water at 1:50,000 killed 100 percent of 
Pier is rapae larvae on potted cabbage plants in a greenhouse, whereas 
the yellow decomposition material t even at 1:12,500, killed none. 
Rotenone suspended in water 1:1,000, sprayed on leaves and fed to 
fifth instars as a snndwich, killed allj at 1:5,000 it killed 20 per- 
cent. — F. L. Campbell (60 ) in 1932. 
Tests have shown that neither paris green, nor lead arsenate, nor 
calcium arsenate will give as effective control of imported cabbage 
worms as will derris dusts containing 1.75 percent of rotenone, applied 
at the rate of 12 to 15 pounds per acre, or pyrethrum dusts containing 
0.12 percent of pyrethrin I and applied at the same rate. Hellebore 
was found to give better control than the arsenicals but was consider- 
ably inferior to the derris and pyrethrum products. — United States 
Department of Agriculture, Bureau of Entomology ( 434 ) in 1933. 
Stahl (389 ) in 1933 reported that at Sanford, Fla. , rotenone 
1.6 percent at 1:200 and rotenone 5 percent at 1:800 did not appear 
to be sufficiently toxic, either as a contact or a stomach poison. 
Derris dust (3 percent rotenone), 1 part in 4 parts of an inert carrier, 
gave very good kill, even without the addition of pyrethrum powder. 
This combination having approximately 0,6 percent of rotenone gave 
better results as a contact dust than did a proprietary cube dust of 
the samo rotenone content. 
A derris-dust mixture (20 parts of derris of 5-percont-rotenone 
content, 40 parts of tobacco dust and 40 parts of 300-mesh dusting 
sulfur) is very effective. — Allen (ll) in 1934. 
The United States Department of Agriculture, in a press release 
dated January 13, 1936, chllod attention to certain disadvantages that 
bar the use of rotcnono insecticides for some types of insects. Derris 
is not effective against all insects but does kill the common cabbage 
worm. 
