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cube sprays of the same rotenone content, the difference "being explainable 
on the "basis of the total extractives content, which was 18.6 percent 
for the derris and 12.3 percent for the cube; the addition of pyre thrum 
extract aided in killing thrips but did not improve the effectiveness 
of the sprays against the red spider; with sprays of the same rotenone 
content, containing sulphonated castor oil as a spreader, the result 
was a better kill than v/hen either alkylphenylbcnzenesulfonic acid, or 
rosin residue, was used. 
In a second series of experiments, using the same insecticides 
as in the first but applied for times at weekly intervals, approximately 
the same results were obtained, except that on tomatoes the spray containing 
derris, pyrcthrum, and alkylphenylbcnzenesulfonic acid appeared to be as 
effective as the sulphonated castor oil sprays. None of the sprays except 
lauryl thiocyanate caused any permanent injury to either tomato or cucumber. 
Chamberlin (70) in 1938 reported that experiments and observations 
during the last several years have indicated that finely ground and 
sterilized tobacco dust is the most satisfactory diluent for cube or 
derris when applied to shade-grown tobacco in combating the tobacco flea 
beetle, Epitrix p arvula Fab. The addition of clay to the customary cube- 
or derris-tobacco dust mixture used for combating the tobacco flea beetle 
apparently did not improve its dusting qualities when applied with rotary 
hand-operated dusters. It appeared that the use of a dust mixture 
containing 1 percent rotenone, with 75 percent tobacco dust and 25 percent 
finely ground Georgia clay as a diluent, on shade-grown tobacco under 
favorable weather conditions at the rate of 6 pounds per acre did not 
leave conspicuous residues on the cured tobacco leaves. Heavier appli- 
cations of this dust mixture, however, did leave conspicuous deposits on 
the cured product. In general, these experiments demonstrated that the 
addition of finely ground clay to the derris- or cube-tobacco dust 
mixture did not result in any appreciable improvement in the finished 
dust mixture and may cause a permanent white residue to remain on the 
treated leaves. 
Cressman (97) in 1938 reported tests of sprays applied to lemon 
trees heavily infested with California red scale. 
One percent of a heavy petroleum oil was used in all treatments. 
One application consisted of oil alone. I n a second treatment nicotine 
was added at the rate of 1 part of nicotine to 1800 parts of total spray 
liquid. In a third treatment an extract of timbo was used to give a 
rotenone concentration of 1 to 10,000. The ratio of total extract of 
timbo to rotenone was 4 to 1. The concentration of toxicants in the 
third spray was not determined. 
Determinations of the relative efficiency of the different treat- 
ments were based on counts of the late gray and later stages. Population 
density was estimated from the number of scales counted per leaf and the 
average number of scales counted per square centimeter on quarters of 
lemons. 
