Sx^osur- to 
wpathor (dr.-s) 
Insects 
nsod 
P^rc 
1 
^•nta 
2 
11 in 
__u_ 
100 
55 
20 
12 
U 
d-. 
5 
1 
^5 
25 
2^ 
25 
25 
lb 
10 
\. 


56 
U 

u 
5U 
55 
o ■ 
12 
U 
2 
55 
7 
^ ........ ... 
5 
20 
12 
U 
Dust usif=^d 
Before 
duRtin/: 
June 
16 
June 
IC!.. 
Pounds 
25.7 
Kunbf^r 
io6 
llU 
ilu-nter 
501 
2b. 1 
131 
^'3 
527 
10.^ 
ikS 
2 
20U 
A t,^':.icnl ex^rrolr -.f control of fle= b-ptl'-' in the field with drrris 
and prrrthr-.Ti on Junp 15, 193^, is gh'^vrn in tho following: tatle: 
Beetles f'^ujid 
Dust usf^d Beforf 
Material 
0,20 percent prr^tbrun 
0.50 p^Tcent pyrethrun 
diluted with talc 
Dcrrifl (0.75 percent 
rotenone) 
Th-^- United Statos Depart^i'^nt of A.:ricultur-, Buropu of Entomologj"- 
snd Plant Quarantine ( 390 ) . in its annual report fr-.r 1^35 report'^d that 
derris -nowder hop shown excellent promise as a control for the to"b?cco 
flea "beetle, esDociall," in the geedteds. Similar control was obtained 
in the field, "but the cost 'f cuch tre^^tnr-nlg had not "b'-'^n det'^rnlned. 
White (^fl2) in 1P35 recom-Tended derris-tobacco dust (2 percent of 
rotenone) at tho rate 'of 1 r-oxind per 100 souare yards of plant "br-d for 
the control of flea beetles on tobacco. 
Chamberlin (71) reported in 1936 fro^ Qi.iincy, Fla. , th^^t recent 
laboratory and field ex^eri'-ients desii'nrd to det'-minp the loss in toxic- 
ity of cub«- duat as a result ef pxr.osure tn direct sur.llc^iht ha"e <shovn 
that the toxic pror^e-ties of a cube-dust nixture with denicotinizr-d tob- 
acco dust as a diluent decreased r?-^idly when this dust -ixture was sub- 
.iected to direct sunlif-ht, and neasured by its toxicity tn the tobacco 
flea 3ef tie. Thece experirnents also disclosed thr-t the cub"-dnst "lixture 
conteinin-^ 1.5 percent of rotenone maintained its toxicity much lon^cT than 
did a dust nixture containing 0.5 percent of rotenone, A cuo--^-dust mixture 
cont-^inin:: 1 percent -f rotenohe killed 7U pfrc^nt of the tobacco flea beetles 
after the dust mixturr had be'-n erriosed tr direct sunli Jit for 2- hour* which 
was enui^'alpnt to approxi lately UG hours' exposure und^r field conditions. 
In performinfi- theo>- experiments it vras not t^os'^ible to make rrorer allowance 
for tv'o i-portant influ'^^nces which ordinsirily occur 'indcr normal shade- iTown 
tobacco condition-*, n^nely, the wetting o-ffrct ^'f hea^y dews and thp dens^ 
sha/.e which ^^.revails within a crop of maturing shade-.Trovn tobacco, Consp- 
auently, it is -orobable th^t und^r rctual field cor-diti'^n" cuh^^-dust mixture* 
will retain their insocticidrl efficiency ageinst the tobrocco flr;^ beetle 
for 9 lonii-"r lorriod t^^/^n was indicrt^d by thesf '^xr^rrimnnta. 
