- U6 - 
Tho Wisconsin i-axi cultural Experi.-nrnt Station ( Ul6 ) in 1Q77 ro^^ort^d 
that derris powdpr^ 3 P'^unds prr 100 sipllonj? of vf^tev plus an "oleated 
reginou? soap" as a spreader was? al.Tinp.t 100 percent f-ffective in I936 a,^ainpt 
thf> larvae and adults of the thrc^-linad lena attacking potatoes and' Japa.^- 
esp lanterns. 
Leptinotarsa decr-nlir.rata (Say), the Colorado potato "b'^etl*^ 
Mclndoo, Sievers, and Ao.ott ( 26b ) in I919 reported that d'^rri'? 
powder as a stomach poison was' tested on a s''iall scale against "ootato 
"beetle larvae- at several stren.^ths, rangin-:^; from 1 pound of powder to 16 
gallons of water up to 1 pound" to 12B gallons, and was found to "be vrr^' 
effective. Practically all the larvae vem killed within U8 h'-urs ond th- 
plants were little eaten. As these sioray nirturer: night have acted as 
contact poisons, "because the larvae vrcre already on the plants when the 
latter w-'-re sprayed, a second series -"f te?;ts was arranged t'^ eli^ninate 
this factor. The sane plants v;ere used and from 20 t^ Uo larvae wore r'laced 
on them 1 or 2 days after they had c-on sprayed. The result?! oVtained'were 
practically the same as in the first series of tests. Ver'- few living; lar"«7-ae 
were found 3 days later and the plpnt^ vr^re little eaten. When apr^lied as a 
dust, derris was equally efficient against potato bertlr larvpe. The. alc"^- 
htflic extract of Derris elliy tica in the rati'-' of extract from. 1 pound of 
powder to 50 gallons of water killed 96,6 percent of the larvae and 2Q,1 -of^r- 
cent ef the ?^dults, 
Brit tain (5^) in I92U described insectary feeding:, tests, made in Fiske 
trays with potato TDeetl": larvae. Arsenate of lead (paste), 2 pounds to Uo 
imperial gallons, was cmpared with various contact poisons, namely, nico- 
tine sulfate, fish-oil soap, and derris povrder, an attem.pt "boini?: made to use 
the last "both as a contact insecticide and as a stomach pois'^n. To te«?t the 
contact acti'-n of derris the -insects were placed in a wire "basket and di-^^ed 
in the solution, then drained pxd fed ^n unsprayed lepves, ■ ' " ■• 
.To test the int<^rnal action ^f derris the 
leaves wore dipped in t'ne solution and fed to the insects. The experiments 
lasted fr-.r a week, daily records i;'''inc ti^kcn. The i':8t notable res\ilts of 
the tests were those o"btained in the case -f derris, which in all streni'ths, 
ranging from. 3 pounds to 100 imioerial gallons to 1 ounce to 100 im-n^rial 
gallons, and with "both n.eth'ds, destroyed 100 percer.t -f the insects, in- 
clr.ding half-grown and fully grown gru'Ds and adults. It seems certain that 
this material did n'^t act as a stomach r^oison, •■r-cause th^' "ceetlep w^re f-^und 
dead in th^ trayn , with no evidence of feedin,,;. 
The extrem-- toxicity of this material to rotat'^ "Deetleo ip <?}i'-wn "by 
thf- fact th^t 1 week after this experiment was concluded a num'b'-'r -^f last 
instara were placed upon untreated lea-'^es in a tray. The nert mornin-: the 
insects were found dead in the "bottom of the tray without e-"-'- r having fed 
on the leaves. This tray had "t'Pen v.ned. in the previous week's test for one', 
of the derris treatments (l o'lnce to lOQ imperial gallons), and evidently 
sufficient sol^.ti'-n had heen taken Tip by the cheesecloth "bottom ^f the tray 
to cn.uae the death of the insects. In comparing these results vrith t^'^se of 
field tests, it appears that the material is much more effective under in- 
sectary cor.ditio;'.p. 
