- 3 U- 
satisfactory control of the pest was unobtainable during the summer, ever, if 
the same insecticides were applied at two or more tines the strength found 
effective in the first instance. Consequently sprays containing dcrris as 
the active principle appear unlikely to replace petroleum-oil emulsions for 
general use, and further work is necessary "before they can he recommended for 
use early in the season when risk of edena is greatest. This station (oO) , 
in 1938 reported that dcrris extract added to a petroleum-oil emulsion was 
more effective against red spider mites than derris only. 
Miles and Miles (lC_5) in 1935 reported that recent work had indicated that 
sprays containing derris or extract of pyrethrum may prove of value in control 
ling red spiders. Derris sprays '"ere used extensively against red spiders on 
hops. With derris sprays there is no risk of injury to delicate plants. In 
this publication Polvosol was advertised by Cooper, KcDougall, and Robertson, 
Ltd. Talding, Kent, for the control of red spiders. Polvosol is a highly 
concentrated liquid preparation of derris, which kills at 1:U00 and is 
particularly suitable for plants susceptible to edema. 
Jary (79) in 1935 reported tests of insecticides against the red spider 
on hops, "indications were that the toxicity of a derris spray to the mite 
may be greater some hours after' its preparation than when freshly prepared. 
k derris st>ray of O.OO56 percent of rotenone content enc containing O.O30 
percent of* sulfonated Lorol appeared to give a complete control at the second 
application, whereas it failed to do so at the first. Jary (80) in 1936 agair 
reported the results of spraying potted hop plants for control of this mite. 
Two derris extracts diluted to 0.005 percent and 0.002 percent of rotenone, 
respectively, were without appreciable effect when two applications were made 
with a knapsack sprayer. Pyrethrum extract also proved ineffective. Lime 
-sulfur 1:79 S ave the tost resu lts in pot experiments, and proved successful 
in the field when a wetter '"as added. 
Tctranyc.hidae (unidentified spocies) 
Carlos (Hi) in I92S reported that red spiders are among the chief pests 
that can be easily exterminated by the application of insecticides containing 
derris or its products. 
The Institute of Physical and Chemical Research (78) Tokyo, Japan, in 1927 
reported that Nootoh, at the rate of 1 pound per 80 imperial gallons of water, 
killed 100 percent of the red spiders. 
Schmitt ( 13U ) in 1930 reported that dusting with dry powder of the finely 
pulverized root of Derris eiliptica "as not effective against red spiders. 
Andries (5) in 1932 recommended Derrisol and Katakilla for use against red 
sniders in South Africa. 
