- 51 - 
Formulae for Dust Mixtures (cont'd) 
To make To make 
0.75^ dust 0.50,.: dust 
No. 2 Powdered air-floated derris or 
cubo root containing 4 percent 
rotenone. 1C-3/4 pounds 12-1/2 pounds 
Talc or in^rt clay 81-1/4 pounds 87-1/2 pounds 
The rotenone content of the finished dust should not bo loss than 
0.50 percent, and it is believed that the use of the 0.75 percent dust may 
be justified in view of the better protection afforded. Twenty to 25 pounds 
of tho finished dust should be applied per aero at each dusting. 
Many of the proprietary rotenone insecticides now on the market will 
give good r .suits if used according to the instructions of the manufacturer. 
Nine different combinations of insecticides were used in triplicate 
on seedling cotton as a control for thrips. Only one application of the 
materials was made. The following table shows the percentage of reduction in 
thrips population in each case. ".Then the plants were practically mature in 
size, a count was made of injured stalks to determine any difference in 
protection given by the various materials used. The stalks considered as 
injured were those having two central stems instead of one. 
The results of this count is also shown in the table. The stalks 
were counted on one row out of each of the six-row plots. 
Tests of Insecticides for Control of Thrips, 
Pee Dee Experiment Station 
Application of May 13 Percent 
Reduction Stalks Stalks Percent 
of thrips injured uninjured injured 
Rotenone 15/* 
Sulfur 42.5/ 
Tobacco dust 42.5/ 65.56 147 144 50.52 
Cheok 47.62 156 124 55,71 
Paris green 10/ 
Sulfur 90.: 100.00 116 178 3S.46 
* This probably means 15 percent of a material containing 4 or 5 percent of 
rotenone. 
