-115- 
for all Combinations, "but the cube remaining after 5 days killed an 
average of 42 percent of the test insects, as compared with a 17-percent 
mortality in the controls, indicating that, -on the average, toxic 
material still remained after 5 days ' exposure to weathering. . Soray 
suspensions of cube with adherents and spreaders gave a greater total 
mortality over a period of 5 days than did dusts with four different 
diluents. However, the kind of spreader or the kind cf diluent made no . 
appreciable difference, indicating that the choice of either could be 
based on availability and price. Although the water suspension without 
adherents or spreaders utilized only about half as much cube per acre as. 
did the dusts, it gave equally good kills* Precipitation was second to 
duration of exposure in causing decreases in the- effectiveness of dube 
dusts and sprays. This was indicated by a significant correlation 
(r = 0.7^ between the decrease in mortality during H-day periods of ex- 
posure and the logarithms of the total precipitation recorded during these 
respective periods. 
The imported cabbage worm can be controlled with a rather dilute 
rotenone dust. — Howard and Mason ( 196 ) in 1937. 
Hut son ( 209 ) in 1337 recommended derris for the control of .the im- 
ported cabbage vorm. A good insecticidal dust contains 0.5 to 0.75 per- 
cent of roter.orie. Suitable diluents are talc,/bW%»nite, chalk, tobacco 
dust, flour, or sulfur. Five pounds ground derris with 1 pound of poi^dered 
skim milk, 2 gallons of skim milk, 3 pounds of thoroughly dissolved soap,, 
or 3 to 6 ounces of one of the sulfated alcohols make 100 gallons of 
effective spray. 
Kelsall and Stultz ( fffo ) in 1937 reported laboratory tests of derris 
(Vpercent rotenone) as a dust, with gypsum as a diluent. Results were as 
follows : 
Concentration 
of derris Mortality ■ 
Percent Percent Days 
-flOO 2 
1 • 
I 67 
12.5 f 20 2 
\ 100 1 
A derris-gypsum dust containing 5 percent of derris gave a thorough 
and practical control in field tests. 
Manschke (268) in 1957 reported on tests carried out with aqueous 
suspensions of derris-root powder against a number of insects. The re- 
sults against imported cabbage worms on cabbage are given in the accompany- 
ing tabulation. In the sprays tested the amount of derris powder ranged 
from O.U5 to I.36 kg. in 37#»5 liters of spray. 
