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effective as the sulfonated castor-oil sprays. None of the sprays except 
lauryl thiocyanate caused any permanent injury to either tomato or cucumber • 
Boyce and Prendergast (14) in 1938 reported that, aside from the regular 
oil spray, there are several materials or combinations of materials including 
oil at low dosage plus rotenone-bearing materials, that may be used in the 
control of the citrus red mite. Combinations of rotenone-bearing materials, 
such as derris, cube, tira'bo,, ,and others with a low dosage of oil (0.5 to 0.7 
percent), have been in use for several years. Such combinations have generall:, 
afforded satisfactory control of the black scale but have been definitely 
inferior to a regular dosage of oil in red snider control. Experimental work 
with these combinations, together with extensive field observations of 
commercial treatments, indicates that when from 1/2 to 2/3 of 1 percent of 
licht-medium oil is used with anv of the more commonly used rotenone-bearing 
materials the average length of time that red slider control may be expected is 
about 3 months. With thorough application, the kill of ell stages, except the 
egg, is usually as good with these materials as with the full dosage of oil. 
The amount of egg kill, however, appears to be directly related to the amount 
of oil deposited and the nature of the deposit. Therefore, the period over 
which these materials effect satisfactory control is largely determined by 
climatic conditions and other factors affecting the development of the spider 
after treatment. The oil-rotenone mixtures are relatively expensive when 
considered in the control of the red spider alone; however, when considered in 
the combined control of aphids, the red spider, and the "off-hatch" black scale 
during the spring, they are very practical. Of the available materials (Selc- 
cide excepted) that may be used at this season for red spider control, the 0.5 
percent light-medium oil plus rotenone-bearing materials is nerhaps the safest 
and is generally most effective. 
Hamilton (70) in 1938 reported the results ofjtests of cube and derris 
ponders (4 percent rotenone and 15 to 18 percent total extractives), applied 
as a spray at the rate of 4 pounds per 100 gallons, with the addition of 4 
pounds of rosin-residue emulsion. Cube powder appeared to be as effective as 
derris powder in the rosin-emulsion spray, both as a contact poison and as a 
repellent. These tests were made- by members of the National Shade Tree Con- 
ference under a cooperative project -ith'the Hercules Ponder Company, manufact- 
urers of rosin residue, and 5 of the principal suppliers of derris and cube 
powders. Sufficient spr^y material to make from 500 to 1,000 gallons of 
diluted spray was sent to each of 38 cooperators in 14 States, together with 
instructions for using the spray and a report blank to be used in giving the 
results of the tests. In 4 out of 6' tests, the sprays were satisfactory agains- 
snider mites on spruce, juniper, and privet., but probably were not effective 
against the eggs. 
The Massachusetts Agricultural Experiment Station (99) in 1^37 reported 
that further- studies of pyrethrum and cierris extracts as us*d in commercial 
sprays showed that the red spider mite is not satisfactorily controlled by 
pyrethrum extracts, but that extracts, of derris, either as rotenone or as other 
extracted resins, principally deguelin, terhrosin, and toxicarol, gave satis- 
factory control, when used in the proper concentration. The emulsified extracts 
containing 10 percent of sulfated alcohol as a netting and spreading agent wer._ 
diluted 1:200 for application. A snray' containing 1.5 percent of ^yrethrins ha< 
