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of it will pass through a 200-mcsh sieve and all the material should 
pass through an 80-mesh sieve. 
The Colorado Agricultural Experiment Station (75) reported in 1936 
that during 1934 the insect infestation on cabbage and cauliflower con- 
sisted largely of the imported cabbage worm. A satisfactory control was 
obtained with pyrethrum dusts containing 0.18 percent of pyrethrins and 
with derris or cube dusts containing 0.5 percent of rotenonc. The min- 
imum amount of material and the number of applications to give seasonal 
protection remain to be determined. The infestation of the imported cab- 
bage worm was so light in 1935 that this part of the work could not bo 
completed. This station (76) in 1937 reported that rotenone Was found 
to be superior to pyrethrins in controlling the imported cabbage worm, 
and that 2.84 pounds of rotenone dust per acre gave a significant kill. 
Cottier (83) in 1936 reported excellent control of white butterfly 
larvae on cabbage in New-Zealand by the application of derris dusts and 
sprays. Derris plus summer-pil spray gave excellent control, whereas 
the oil sprays alone gave poor control. Dusts were slightly superior 
to the spray. Cottier recommended replication of e dust containing from 
0.5 to 0.75 percent of rotenone at the rate of 20 to 25 pounds per acre. 
He also tested e number of proprietory derris dusts and sprays. In 
1939 Cottier (84) reported that in Few Zealdnd derris sprays and dusts, 
at least when fresh, gave excellent control. Some of the derris-spray 
materials, however, had markedly deteriorated in killing power in their 
second season. One of the proprietary powders (D. P. No, 6) gave good 
results when bought on the market, although it was not possible to tell 
when it was manufactured; and another (D. P. No. 8), although it also 
contained pyrethrum extract, gave good results after storage for three 
seasons; therefore a considerable variation is to be expected with 
commercial brands of derris-spray powders. On the other hand, all der- 
ris dusts of 0.75-per cent-rot enono content retained their killing power 
well. In the field D. P. No. 2, which contained 0.5 percent of rotenone, 
gave good control of caterpillars 'when applied at 20 to 25 'pounds per acfe. 
Summer-oil sprays even at 1:60 did not give satisfactory results, but 
when derris spraying powder was added to the oil excellent results were 
obtained. 
Gui ( 171 ) in 1936 reported that in 1934 a spray of 1 part Rotecide 
plus 1 part, New Evergreen to 800 parts water controlled 95.7 percent of ■ 
the imported cabbage worm, and that a derrms-clny dust (0.5 percent rote- 
none) gave cEOO-purccnt control. In 1938 Gui ( 172 ) reported that for the 
protection of cabbage against three species of cabbage worms, including 
the imported cabbage worm, the crop should be dusted or sprayed at 10-day 
intervals with paris green or derris powder. Derris-powder dusts should 
contain not less than 0.5 percent of rotenone, and 1 pound of derris pow- 
der of 4-pcrccnt-rotenono contont should be used to 7 pounds of the diluent, 
Desirable diluents arc flour, talc, diatomaceous clay, dusting gypsum, 
and finely ground tobacco stems. Derris-powder sprays should consist of 
1.5 pounds of derris powder (4 percent rotenone) in 50 gallons of water, 
used with n spreader and sticker. When other grades of derris powder are 
used, spray should contain 0.015 percent of rotenone. 
