-35- 
Kearns, Marsh, and Pearce (84) in 1933 reported that derris spray gives 
a good measure of control of the red spider. Commercial experience with 
derris as a means of controlling apple pests in England is limited end the 
results have "been variable. The indifferent results ere probably due to the 
use of too low a concentration of the toxic principle (rotenone) . Derris 
is used mainly in two forms for the preparation of washes: Finely ground 
derris root added to a week soap solution, and en oil emulsion consisting 
of a derris extract in a mineral or vegetable oil. The, duration of effective 
toxicity after the application of some preparations may he several days, but 
critical data on this point are not available for apple pests. . Derris dusts 
have not been used to any extent on apples. 
Keerns, Marsh, and Martin ( 83 ) in 1935 reported trials carried out the 
wrevious year at Long Ashton, England, with combined sprays for the simul- 
taneous control of the red snider, caterpillars, end the plum sawfly on 
plums. At Finvin trials ^ere carried out on trees of the variety Czar. 
Double spraying was enroloyed, and t^o types of spray were tested in the second 
application. For the first amplication, on May 11, 7 days after petal fell, 
the following mixed spray was used: Colloidal lead arsenate 2 pints, nicotine 
8 ounces, lethelete netting -preparation 8 ounces, and water 100 gallons. 
The second application was made on May 29, when half the trees previously 
sprayed on May 11 received the following spray: Refined petroleum-oil 
emulsion 1.5 gallons, lead arsenate powder 4 wounds, and water 100 gallons. 
The remaining half of these trees was sprayed on May 29 with a derris-arsenate 
spray of the following composition: Ground derris root (2 percent crystalline 
rotenone) 2 wounds, lead arsenate -powder 4 wounds, lethalate wetting prep- 
aration 8 ounces, and water 100 gallons. The control of the red spider was 
satisfactory in both types of treatment employed, end no foliage damage was 
recorded. 
Van der Lean ( 90 ) in 1936 reported that Tetrenychid.ae are sensitive to 
derris. 
The East Mailing Research Station, England (55) in 1936 reported that a 
proprietary derris powder was used in the routine spraying program in 1935 
for the red spider on apples (l-l/4 pounds -f- 5 pounds of soft soap per 100 
imperial gallons of water) . 
Steer ( 140 ) in 1936 published a summary of the use of derris as an 
insecticide in England. On damsons in 1934 derris and soap, applied on May 
18, was substantially as effective as lime-sulfur for the control of red 
spiders. The reduction caused by these sprays in the amount of red spider 
injury, and the reduction in numbers of summer eggs subsequently laid on the 
leaves, was 92 and 97 percent, respectively. Derris showed great promise and 
is worthy of trial for the control of red spiders where lime-sulfur eannot be 
used with safety. 
The University of Bristol, Agricultural and Horticultural Research 
Station at Long Ashton, England ( 16 ) , in 1936 reported that derris was the 
most satisfactory' spray for the control of the red spider. 
