-68- 
When used undiluted or nixed "'ith equal parts of 
finely ground tobacco dust or sulfur, ground derris root 
proved to be more toxic to each of the three species 
studies than the other materials tested. It apparently 
has a residual action, which pyrethrun dust does not have. 
Plants dusted ""ith derris appear to be more thrifty and 
freer fron thrips than those dusted ""ith other materials. 
The data indicated that dosages of 3 to 6 pounds (nixed 
^ith equal amounts of tobacco dust) per acre per applica- 
tion, applied under favorable conditions, "'ill effectively 
control the cabbage looper, the common cabbage ,r orm, and 
the larvae of the diamondback moth* Derris caused certain 
discomforts to operators, including slight tickling and 
irritation of the respiratory organs and, if breathed for 
a long period, slight nausea. No plant injury occurred. 
Derris r^ith sulfur, 1:3, and derris, tobacco dust, and sulfur 
1:4:5, '"ere also tried. The relative susceptibility of the three 
species to a mixture of equal parts of derris (rotenone 4.9 percent, 
total extract 18.8 percent) and tobacco is sho^n in the following table 
of results obtained at Chadbourn, N. C. 
Relative susceptibility of cabbage worms to derris and tobacco 
Time 
appl : 
of : 
LCa-: 
Bate of 
applica- 
tion/acre 
Reduction in number of vorms per plant 
as compared -rith undusted plots (percent) 
tion 
Loopers: Diamondbacks : Common cab-: All 3 
: :bage <"om.s : species 
p.m. 
a.m. 
17 
16 
74 100 100 83 
46 69 100 57 
White (481) in 1935 summarized the results obtained 'oy the Bureau 
of Entomology and Plant Quarantine at Chadbourn, K„ C, , Charleston, S. ( 
Baton Rouge, La., and Columbus, Ohio, "-ith nonarsenical insecticides 
for control. As a general insecticide for the concvol of mixed popu- 
lations of the four species of cabbage "-orris involved, derris gave 
the best results and pyrethrum came next. In comparison, paris green, 
cryolite, and calcium arsenate '"ere approximately equal in effective- 
ness but, in general, "-ere inferior to either derris or pyrethrum. 
Based on comparative efficiency, at economical strengths, dermis and 
pyrethrum -ere approximately equal in effectiveness in controlling 
the looper, and either "-as more effective than paris green, cr.'-jlite, 
or calcium arsenate.. In general, better rebults ,:, e.re obtained vith 
dust mixtures than "-ith sprays. The dusts '"ere applied »ith rotax 
type hand dusters in such a manner as to cover thoroughly all infested 
portions of the plants, care being taken to reach the insects "-ith the 
dust whenever possible. The rate of application ranged fror 15 to 20 
pounds per acre per application, according to the size of the plants. 
Applications vere begun "-hen the vorns firs': appeared on the plants 
and "'ere repeated as often as w as necessary to protect the crop.. 
Usually three applications ""ere nade per crop. Dc .'is duets, cither 
hone-mixed or commercial, containing from r 5 to 1,0 percent of roten- 
one, gave the most satisfactory results of any of the insecticides 
tested, in four sections of the Central, Eastern, and Souchern States. 
