- 9 - 
In the field 99 percent of the apple aphids were killed when 
sprayed with a suspension of rotenone 1:60,000; and 77-2 percent were 
killed "by a dust containing 1 part of rotenone and 99 parts of diatoma- 
ceous earth. — Davidson (6^) in 1930. Fulmer ( 113 ) in 1930 wrote that 
the green apple aphid can "be effectively controlled "by spraying with 
derris powder, 5 pounds per 100 imperial gallons. 
Ginsburg and Schmitt (12_5) in 193 2 compared the contact insecti- 
cidal action of rotenone and the pyrethrins on apple aphids. Apple twigs 
infested with these aphids were dipped in solutions of various concentra- 
tions of rotenone, derris, and pyrethrum extracts. Both rotenone and 
derris extract proved much more toxic to aphids than did pyrethrum ex- 
tract. Rotenone at 1:10,000 killed 93 «^ percent of the apple aphids in 
2h hours; derris extract (rotenone equivalent to 1:13,200) killed 93 per- 
cent. 
Ginsburg and Granett ( 122 , 123 ) in I93U tested on the green apple 
aphid untreated derris powder and also the marc after extraction with 
acetone or with acetone followed "by water. The materials were applied in 
the form of coarsely and finely ground dusts. Derris-root dust (rotenone 
U.l percent) was more toxic against aphids when applied on wet than on 
dry foliage. Residues from derris root extracted with acetone possess 
practically no toxicity to aphids. In 193? *he same workers ( I2U ) studied 
the compatibility of derris in combination with other materials in tests 
on A. pomi . The addition of lime, lead arsenate, or sulfur, singly or 
combined, tended to reduce the aphicidal properties. It also appeared 
that with a good wetting agent a suspension of fine derris root was as 
efficient as a dispersion of a commercial acetone extract. Liauid lime- 
sulfur appeared to exert a deleterious effect on the aphicidal properties 
of derris. nevertheless the combination of derris root and lime-sulfur 
with a spreader gave sufficiently good results against the green apple 
aphid to warrant tests as a substitute for nicotine-lime-sulfur in the 
field. 
Ginsburg, Schmitt, and Granett (126, 127 ) in 193^ reported on the 
toxicity of various extracts of derris root to sucking and chewing in- 
sects. Tv.'o extracts of derris root, one containing a high percentage of 
rotenone, the other no rotenone, were equally toxic to aphids in dilu- 
tions of 1:20,000 or lower. 3ased on tests of extracts with different 
species of insects, including the green apple aphid, the following con- 
clusions were drawn: 
Water-soluble organic solvents such as acetone and alcohol 
are able to extract practically all of the water-soluble and 
"atcr-insoluble ingredients of derris root that arc toxic to 
sucking insects. Either continuous distillation, or soaking 
with subsepuent filtration and washing, extracts all the active 
< principles that act as contact poison when acetone or alcohol 
is used. Water does not extract all the toxic principles of 
derris root. At low dilutions the water extracts compared 
well in toxicity with acetone and alcohol extracts, but pro'*ed 
inferior to them in high dilutions. Water extracts rapidly 
deteriorate on standing, with resultant loss of toxicity. 
Alcohol extracts slowly lose toxicity upon standing. Acetone 
extracts do not show any appreciable changes in toxicity upon 
*TSTZ PLANT BOARP 
