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of fumigation, However, in orchards where the red scale is a p rob 1 err., 
in the light of present knowledge it would appear that these sprays, even 
with the higher dosages of oil, should not be substituted for the regular 
oil spray and fumigation program. 
The Leffjngwell Company in 1937, in a letter to R. C. Roark, stated 
that when Tox-a is used with oil it is fairly effective against the citrus 
red scale, and is superior to oil alone. 
The California Fruit Growers' Exchange, Bureau of Pest Control (43) 
in November 1938 reported on the use cf rotenone-oil products for the con- 
trol of the red scale on citrus. The extent of red scale kill has been 
directly related to the amound of oil used, without regard to the addition 
of botanical powder. On the whole, the minimizing effects of these 
lower dosages of oil on water rot of ?!avcl oranges has not been particu- 
larly pronounced. Furthermore, r.hen more than 1 percent of oil was used 
with rotenone, the cost over regular-dosage oils was increased. 
LaDue ( 179 ) in 1938 reported that during the winter of 1936-37 
tests were made on a number of organic solvents from the standpoint of 
(1) the solubility of the derris resinate in the solvent: (2) the solu- 
bility of solvent in the spray oil; (3) the solubility or suspensibility 
of the derris resinate-solvent irixture in the spray oil; (4) the solu- 
bility of the solvent in water; and (5) the toxicity of the mixture to 
certain scale insects. The main groups of the solvents tested were (l) 
alcohols, (2) alcohol-ethers, (3) ethers, (4) glycols, (5) aldehydes, 
(6) ketones, (7) esters, (c) aliphatic amines, (9) chlorinated products 
of the saturated hydrocarbons, (10) phenols, (ll) benzene and benzene 
derivatives, and (12) the essential oils, Cnly a few compounds in each- 
group were tested. The higher ketones appearee to give the best results 
from the standpoint of solubility of the derris resinate, stability cf 
the resulting mixture, and added toxicity to the spray oil. Other com- 
pounds such as 2,2 f -dichlorethyl ether, sassafras oil, and the higher 
acetates appeared to be good solvents for derris resinate, and experi- 
mental data seem to indicate an added toxicity to the spray oil. A. 
aurant ii was used as the test insect. 
Derris resinate is not very soluble in highly refined petroleum oil 
such as is used in the spraying of citrus. Thus, when an appreciable 
amount of the derris resirate-solvent mixture is added to the oil, a sus- 
pension of resins and rotenone is formed. In the early part of 1937 
laboratory experiments were made using methyl isobutyl ketone, methyl-n- 
amyl ketone, and 2,2 , -dichlorethyl ether as intermediary solvents for 
the derris resinate and tank-mix spray oil. Lemons infested with the 
California red scale were vised for the experiments, Derris resinate 
dissolved in raethyl-n-amyl ketone appeared to give the best kill of the 
three solvents, Sbeling has shown that methyl -n-amyl ketone incorporated 
in spray oil increases the toxicity of the oil to the red scale. Further 
laboratory and field work by Ebeling during the svffiiner and fall of 1937 
also substantiates the above findings with regard to the toxicity of 
derris resinate to the red scale. 
