-135- 
niootine. A spj*ay of derris powder (4 percent of rotenone) and 1 
pint of sulfonated castor oil in 50 gallons of water, is very effec- 
tive.— Weiss and Baumhofer (669 ). 
The toxioity of rotenone sprays to red spiders on carnations 
inoreased with increased temperature. Effectiveness of suspensions 
of derris, cube, or pyrethrum powder in water was less than their 
extracts. Under normal greenhouse conditions* derris or cube powder 
(4 percent of rotenone), mixed with sulfonated castor oil (lt300) 
and diluted at the rate of 2 and 3 pounds per 100 gallons, gave only 
moderate oontrol of red spiders on roses after three applications, 
but good oontrol after four applications.-- Whitcomb (675 , 676) . 
In tests with eight commercial rotenone preparations against the 
red spider on roses in greenhouses, the addition of a neutral copper 
fungicide decreased the efficiency of rotenone sprays. Satisfactory 
control was obtained, after four applications at weekly intervals, 
only with those materials which contained sonie insecticidal ingred- 
ient in addition to rotenone, and an emulsifier. The most effective 
material was technical mannitan monolaurate to which 1 percent of 
rotenone and 2.6 percent of other derris extractives was added. "When 
diluted ( 1:400) this was the only spray material which consistently 
killed 90 percent or more of red spiders without injury to the plants. 
Several of the rotenone sprays, which gave unsatisfactory control of 
the red spider on roses, gave excellent control of it on potted car- 
nations. A commercial spray containing mannitan laurate and rote- 
none (1:400) killed 89 percent of red spiders in four applications; 
at 1:600 strength, 73 percent. Two other rotenone materials gave 
fair control of this pest on greenhouse plants. — Whit comb and coworkers 
(682 , p. 39, 62-3, 67) • 
Tetranychus telarius (L»), the red spider in Europe 
la England infested tomato plants should be sprayed with derris 
extract until the and »f May.— Bewley (49). 
Established infestations of this pest on plants in greenhouses 
in England are very difficult to eradicate, but a simple means of pre- 
venting its establishment has been evolved. Derris powder and soft soap 
are added to the water used for the routine "damping- down" of the 
plants, at the rate of 1.5 and 2 pounds respectively, per 100 gallons. 
The plants are thoroughly sprayed each morning, noon, and night, and 
consequently a thin deposit of derris accumulates on the leaves.— 
Mas see 
lenriy 
(401). 
