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The treatments in which toxicants were used showed a considerably 
higher scale mortality than the application of oil alone. Mortality on 
the leaves sprayed with oil alone ranged from 92 percent when there were 
5 scales per leaf to 21 percent when there were 55 scales per leaf with 
an average mortality of 71 percent. Mortalities in treatments with oil 
plus timbo extract were 91 and 89 percent respectively, with few indica- 
tions of any effect of population density. On the fruit the ranges in 
mortalities as the average infestation of scales counted changed from 
1 to 5 scales per square centimeter were as follows: oil alone, from 
86 to 58 percent; oil-timbo extract, from 93 to 84 percent; oil-nicotine, 
from 98 to 89 percent. There is no evidence that the addition of the 
toxic agents caused any injury to the trees. 
The extract of timbo was prepared by a Whittier, Calif., company 
dealing in this product. The ratio of rotenone to other timbo extractives 
was stated to be 1:4. A mixture of 30 percent trichlorethylene and 70 
percent butyl phthalate was used as a solvent. The butyl phthalate was 
incorporated at Cressman's suggestion in order to provide a relatively 
nonvolatile solvent which would increase the solubility of the rotenone 
in the oil phase. A small amount of this mixture was used in all 
emulsions in order to make them identical in respect to the oil content. 
Emulsions were made up with a high speed stirrer using ground glue 
as an emulsifier. All sprays contained 1 percent of oil. One treatment 
consisted of oil alone. For another treatment, an amount of timbo 
extract calculated to give a rotenone content of 1 part to 10,000 parts 
of dilute spray was added to the soil before emulsification. However, 
there was a discrepancy between the statements on the label and state- 
ments of the company representatives as to the rotenone content, so 
that final information as to the rotenone concentration applied cannot 
be furnished until a sample that has been forwarded is analyzed. In 
a third treatment, nicotine was added at the time of dilution of the 
emulsion in the spray tank to make 0.054 percent of nicotine. This was 
equivalent to 1 part of nicotine to about 1800 parts of dilute spray. 
Turner and Walker (409) in 1938 reported the results of tests 
of insecticides for the control of the onion thrips, Thrips tabaci Lind. , 
in Connecticut during 1933 to 1937. In 1933 an extracted rotenone 
spray (Insect-Nox) plus 0.5 percent (by dry weight) potash-coconut oil 
soap applied twice reduced the number of thrips but was slightly less 
effective than nicotine sulphate at 1:800. 
In 1936 cube dust (0.75 percent rotenone) and cube- sulfur dust 
containing 73 percent sulfur were applied 3 times. There was no satis- 
factory control of thrips, and sulfur caused some injury to the onion 
tops. 
In 1937, cube, cube +Ultrawet , cube+ Aresket , and cube + sulfur 
+ Ultrawet were tried. The' writers conclude as follows: 
"The combination of pure ground cube root with a 
suitable spreader apparently protected onion plants from 
thrips if spraying was begun before the plants were heavily 
