~ 21 - 
The question whoth.^r sprayiig or dusti/.g is nore j'rofitable is 
'".ifficult to p.nswer in thif» case. In gr.neral, less -npt-rinl is usrd in 
spraying than in dusting, but p.^rhaps thr- treatment would hav3 to "be 
repi?atod niors freouer tly since th:? after effect of spraying is vpry poor. 
In the laboratory, beetles confined for 2 days on lea"''"es that had bem 
sprayed v/ith a, strong derria-powder suspension (rotenone l:l,600) shov^.d 
only slight mortality (5 of the 20 beetles). The insects took almost no 
food; thus th^ sprayed leaves, in genral, seem to have had a repellent 
effr-ct. Ktt-'T the beetles had receive'" fresh food th^y again fed nor-'ially. 
The after effect of thr- dusting v;as nuch great'=-r than that of the spray- 
ing; dusted lea-"cs v:er" not only attac'-ced but a considerable percentage 
(about 60 to go percent) of the be'-.tles that settled down on them died. 
This advantage over stiraying, however, is inpcrtant only in ti'nes with 
little r^i.-fall and in cas'-s where the chances of reinf estetion arr gre^t. 
Finally, it has b^f-n concluded that it is desirable to begin the 
treatmrr.t early, to protect the plants during the difficiilt early stages; 
before all, the spraxying or dusting must be regularly re-peated in the be- 
ginning. Thp results that can be obtained were shown in a Luf fa planting 
of the Agricultural Institute, At first this was treated with derris t^'ice 
a week, later once a week; then treatments vrrro begun when the little plants 
were 2 weeks old. While the imtreated Liiffa were continually severely attack- 
ed and shov^ed completely riddled leaves and for this rea.son grev^ slowly, the 
leaves treated vrith derris remained practically whole and the growth vras 
faster. 
C.^TQ^^Hf^- irijf^rjia.ta (Forst.), the bean leaf beetle 
Branncn (_^) in 193^ reported that in r^reliminary tests derris 
sprays containing 0,015 percent of rotf-none were shown to b'^ effective 
against _C. trifurc-^ta . which had bern abnormally abu;:dant in the Norfolk 
section during ytny . The treatment applied to the infested snan. beans 
was the same as thr-t recommended for the control of the Mexican, bean 
b'^-etlc, Beforr treatment of thei^e beans, the foliage in.iurj- causkjd by 
the bean leaf beetle was estimated at from 60 to 75 percent. Eleven 
days after treatment the foliase injury on the treated plots was estimated 
at from 5 to 15 percent, v.'hereas on the untreated r)lotR it ran.eed from "^5 
to Uo percent. 
Fenton ( l27 ) in I036 reconreiided the sam-^ treat-^ent for thi<! b?etle 
as for the Me:eicen beai beetle, that i'^, rott^none dusts and sprays. 
Nettles (29U) in January I03Q reco i i^nd'-'d derris extract for the 
control of tho be-.n leaf beetle in Sout!^. Carolina. 
Hau.le (l?l) in l''\39 recrom lended a dust (0.5 percent of rotenone) 
or a spray (3 pour.ds of cube- or derris of ^ percent rotenone content per 
100 gallons) for th'-^ control of this insect. 
Brannon (U7) in 1939 r^jported tliat a spray containing cube root, 
p.^rethrum, and s'^lfonated castor oil, and ^ dust mixture comncs^d of cube 
plus p.vrethrum flow^n-s, with sulfur as a diluei^t, and containing 0.5 per- 
cent of rotfno o, vrere highly-- to^"ic to the bfisn leaf b'-etle on the storing 
crop of snap bean" at I^orfolk, Va. 
