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In 1938 the same station ( 100 ) reported that in studies of insecticides 
used for the control of the red spider on carnations and greenhouse plants, 
materials containing rotenone continued to show a high toxicity against this 
pest and generally became more effect-ive as the temperature increased. The 
addition of wettable sulfur as a fungicide to one of the rotenone sprays 
caused no material change in the number of red spiders killed. In comparable 
tests most of the newer commercial insecticides containing rotenone were 
inferior to the older standard mixtures or to laboratory preparations. Sus- 
pensions of derris, cube, or pyrethrura powder in water were less effective 
than the extracts of these materials, and the addition of a netting agent 
did not increase their effectiveness in the laboratory. This station ( 101 ) 
in 1939 reported that experiments with sprays containing extractives from 
derris and cube indicated that effective sprays of this nature for combating 
the common red spider, and capable of consistently giving better than 90 
percent contol, should contain 0.03 percent of total extractives (0.0075 
percent rotenone). This is equivalent to a stock mixture containing 1.5 
percent of rotenone and 4.5 percent of other resins, diluted 1:200. Sprays 
containing these active ingredients are slightly more consistent in effective- 
ness if combined with brown camphor oil, rather then with soluble pine oil or 
sulfonated castor oil. The addition of 0.2 percent of Karaya gum increased 
the effectiveness about 5 percent, apparently by building up the deposit on 
the leaves; but ^hen both gum and spreader were added the run-off was 
increased and no benefit from the gum resulted, flhen the temperature was 
80° F. the effectiveness against the red spider was from 25 to 40 percent 
greater than at 60°. An alcoholic extract of derris containing 0.0075 percerv 
of rotenone and 0.0225 percent of other extractives was 10 percent more 
effective than a similar extract containing 0.005 percent of rotenone. The 
addition of 0.005 percent of pyrethrins not only failed to increase the 
mortality of the red spider but actually gave an average decrease of 5 percent 
in three experiments. 
The New Jersey State Agricultural Experiment Station ( 112 ) in 1938 
reported that during the last few years the greenhouse red sr>ider has done 
much damage to roses. In 1937 studies of the effect of derris-oil emulsions 
on this arthropod indicated that these are very satisfactory and cheap 
materials for red spider control. By the use of derris, the amount of oil 
necessary to effect control has been greatly reduced and the danger of damage 
to the rose plants correspondingly decreased. This materiel destroys all 
stages, including the eggs. 
Weigel and Nelson ( 164 ) in 1938 tested derris and cube with various 
wetting agents (including alkylphenylbenzenesulfonic acid, sulfonated castor 
oil, and ammonium caseinete + rosin-residue emulsion) for control of the 
common red spider on greenhouse tomatoes and cucumbers. The authors concluded 
that a. derris spray having a rotenone content of 0.0056 percent is as 
effective as one '"ith a 0.0112-percent-rotenone content when sulfonated cestcr 
oil is used as a spreeder; that the derris spreys used in these tests are 
superior to cube spreys of the same rotenone content, the difference being 
explainable on the besis of the total e^trectives: that the addition of 
pyrethrum extract does not improved the effectiveness of the spray against 
