Q-PHENYLAZOANILINE AS AN INSECTICIDE
By M. C. Swingle, J. B. Gahan, and A. M. Phillips,I/
Division of Control Investigations
During 1940 and 1941 at the Sanford, Fla., laboratory a large number
of synthetic organic compounds were tested as insecticides against 16 species
of insects. One of the most promising compounds tested was p-phenylazoa-illine
(p-aminoazobenzene). It was therefore selected for further investigation
with regard to its general effectiveness as a spray on truck-crop plants.
Most of these investigations were made at Sanford, during 1940 and 1941.
The compound (C6 Hs N: NC6 H4 1Ha) is preferably called L-phenylazo-
aniline, although it is often referred to as p-aminoazobenzene. I is a
yellow crystalline solid when pure, but the color of comLercial samples
may vary from yellow to dark brown. The compound is only slightly soluble
in water but is soluble in ether, acetone, and hot ethyl alcohol.
A pure grade of p-phenylazoaniline was used in these tests. The
derris standard used in comparative tests contained 4.5 percent of rotenone
and the pyrethrum standard 0.33 percent of pyrethrin I and 0.33 percent of
R-Phenylazoaniline has been tested on several species of insects by
different workers, In 1930 McAllister and Van Leeuwen (5) reported rather
poor results with the compound when used as a spray against newly hatched
codling moth larvae. Later Fink and coworkers (2) reported the compound
toxic to mosquito larvae at 20 parts per million in water, and therefore
not particularly promising compared with other compounds reported in the
same paper, Bushland (1) used the compound in jar tests with young screw-
worm larvae and reported it nontoxic by the method used.
On the basis of the results of Fink and coworkers, application for
an insecticide patent was made by D. L. Vivian and H. L. J,. hauler (i), of
1/ A. M. Phillips was transferred to the Division of Fruit Insect
Investigations July 1, 1941.
this Bureau. This patent describes not only R-phenylazoaniline but also
other compounds having two homocyclic nuclei joined by an azo linkage and
having one or more amino groups.
The compound was received from the Division of Insecticide Investiga-
tions for general testing, as described in a previous publication (6).
These tests were designed to obtain preliminary evidence of toxicity, and
then to study in more detail the amount of dust or concentration of spray
required for satisfactory control of various pests, the utility of the
material as a spray on tender foliage, and something of its residual effec-
tiveness when exposed to certain factors of weathering.
Since many organic compounds are specific in their toxicity, it was
considered that a few tests on a large number of species of insects would
be more useful and informative than many replicated tests on a few species.
The compound was therefore tested on 16 species representing 4 orders.
The majority of the tests were made on leaf-feeding lepidopterous larvae.
Nearly full grown larvae were generally used because they are more resistant
to insecticides than smaller individuals. The various species used in
these tests were as follows:
Foliage or grain treated
American cockroach (Per planeta americana (L.))
Cabbage looper (Autog~rpha brassicae (Riley))
Cabbage webworm (Hellula undalis (F.))
Colorado potato beetle (Leptinotarsa
Cowpea weevil (Callosobruchus maculatp s (F.))
Cross-striped cabbage worm (Eve.rgestis
Diamondback moth (Plutella maculipennis (Curt.))
Greenhouse leaf tier (Phiyctaenia rubigalis (Guen.))
Fawaiian beet webworm (Hymenia fascialis (Cram.))
Imported cabbage worm (Pieris rapae (L.))
Melonworm (Diaphania hyalinata (L.))
Rice weevil (Sitophilus oryza (L.))
Southern armyworm (Prodenia eridania (Cram.))
Southern beet webworm (Eachyzancla bipunctalis (F.))
Termites (Reticulitermes sp.)
Yellow woolly bear (Diacrisia vir inica (F.))
Swiss chard and beet
Swiss chard and beet
Preliminary Petri-Dish Tests
Preliminary tests were made in Petri dishes to establish insecticidal
action and to determine the species most susceptible to the compound, The
tests were made by feeding insects leaf sections that had been rather heavily
dusted with the pure compound, as described in a previous publication (g).
Eust was applied to both sides of the leaves, and the deposit was determined
leavesj. >wo le'ves were thit i
Petri C ishes con>Lanin, c to 1 o 25 .
examiC.tion was aue for 0 gtaiiy of -L L
amount of feedng.,imilCr tesK r t 0 e,
insecticides recognlioe LoiC S o _L J
A he d is e -l' ,1n, le i
dusted leaves, mortality might i'su ..i : i
Preliminary tests sise
results presented cor the ...... .
welworm, the imporLed caske L_ we
and Lhe southern ee: c.. cer....
for the other insects r o
species--the Colorco l_ o ,.o Lee e h o-
Hawaiian eet we'evor d the -.
effective s the sLn(r'1 r ico e
100 micr se rcet1ee ..' 1.
limited fecdiug. .he CoI7ou .
the southern &r. ar,, Ind h ac eeol ... '
insectioide. It zas hih) ......
cabbago insects lsted. his p i* ...
also eviCent in h tests e o, I 4-(iile C
insects are usually rA'he, s e. A .
ance to ihese co-punds s f it.!ei r .
) ~ I j~v.
)~ r~ ~
The results of the ....
of toxicity to certain insLects L Co t gve cU
of toxic action. Te help clariy h L d i
subsequent invest _'ions > e et ii 0 "
under certi atosjheric cc i 1,
chemical w-as ,eiohed Iefo i nc ,
(not sunlight) oil a screened poUi r ,
more than 3 percent of 0ho depsit 1. i-t I.
stability for use as a i..... cn c: "
It ws also evident that A the ,. .
to act as a fumigant. !his coni ion e e ced,
test on the maelonworm, the cross-s c e
arm,,x orm cy isolatir.i :---,, l ih er
dishes containing 1.i-e ein" on ,i
the conclusion that p-phenilc u iie i 1 -.
tests reported in table 1.
Table l.-Toxicity of R-phenylazoaniline as compared with a standard insecticide
when dusted on foliage and fed to nearly full grown larvae
of several species confined in Petri dishes
p-Phenylazoaniline Standard insecticide
ct Deposit Kill in Feeding on Deposit Kill in Feediag on
__ 2 days 3 das last day- 2 day last l
U;_ Vn,.m Par + 0 na + U; rn.~e V +rnn V a.,n+
per sq. cm.
W A V W a %,* V&
per sq. cm.
Yellow woolly bear
43 47 Moderate
7 71 Traoe
9 80 do.
0 92 do.
D 90 do.
5 96 Trace
4 99 do.
3 100 do
7 100 do.
5 55 Moderato
5 64 do.
4 71 Trace
3 78 do.
With the toxicity of p-phenylazoaniline established with regard to
certain insects, a study was made of the effectiveness of spray deposits
on potted plants in cylindrical screen cages. For this purpose the copound
was made up as a spray at concentrations of 8, 4, 2, and 1 pound to 10
gallons of water, and each concentration vas applied to tio pln-. with a
compressed-air spray gun until the spray began to drip from the leave.
When the plants were dry, 15 larvae were confined on each plant by a cylin-
drical screen cage. The treated plants were then placed out o; doov in a
sheltered location vnd e-aiined at two-day intervals for larval mortality
and an estimate of the feeding on the plants.
Of the various wetting agents tried, the most satisfactory was
saponin. The spray was prepared by grinding the weighed portion of p-
phenylazoaniline in a mortar with a measured quantity of a saponin solution
(equivalent to 1/8 pound of saponin per 100 gallons of sprav) a'n- then adding
water gradually to obtain the desired concentration. The spray thus for.ned
remained well in suspension, with occasional agitation, and adhered well
Spray suspensions of p-phenylazoaniline were tested a-t inst five
species of insects. The results, presented in table 2, are -verages of
three replicated tests. The compound was very effective againt the cross-
striped cabbage worm and the melonworm, being about equal to derris, which
is very effective on these species. Against the Hawaiian b-et &ebwor.m
p-phenylazoaniline appeared to be slightly more effective than deIrri at all
concentrations. It was definitely inferior to lead ar~enate against the
southern armyworm but slightly superior to this insecticide against the
southern beet webworm.
An experiment was next made to determine the tolerance of certain
tender truck-crop plants to spray deposits of p-phenylazoaniline. The
spray was prepared at concentrations of 4 and 8 pounds per 100 gallons of
water, with saponin, and applied to small field plots of bean, collards,
pumpkin, and swiss chard. After 10 days a second application was made, and
the final results were recorded 20 days after the first application. From
4 to 12 plants of each kind were used with each concentration of spray.
The plants were protected from showers and at night to prevent the spray
residue from being washed off.
The two applications of the 4-100 spray caused no injury to bean and
collards, but they did cause slight injury to pumpkin and c.iss chard.
A few spot burns were noted on the swiss chard, and moderate to s, vere
burning of the old leaves resulted on pumpkin. The t-o applications of
the 8-109 spray caused no injury to collards and only very slight injury
to the old leaves on bean. The injury to swiss chard and pdpkiin was
similar to that described for the 4-100 spray.
Table 2.--Toxicity of L-phenylazoaniline as compared with a standard
insecticide when applied as sprays to potted plants infested with
nearly full grown larvae of several insects
Concentration _-Phenylazoaniline Standard insecticide
Insect of Tests Feeding on Kill after -- Feeding on _Kill after -
insecticide sixt ay 2da 4 days 6 days sixth day 2 days days 6da
Pounds per Number Percent Percent Percent Percent Percent Percent
Cross-striped 8 1 Trace 61 G7 100 Trace 83 100 100
cabbage worm 4 1 do. 70 93 100 do. 83 100 100
2 1 do. 58 83 100 do. 68 100 100
1 1 do, 58 83 86 do. 48 57 S6
Hawaiian beet 8 3 Trace 26 79 94 Trace 22 57 6)
w ebworm 4 3 do. 23 67 85 do. 11 51 68
2 3 do. 7 32 77 do. 6 38 60
1 3 Moderate 4 34 50 Moderate 2 23 37
Melonworm 8 1 Trace 73 100 100 Trace 30 56 95
4 1 do. 64 100 100 do. 23 74 98
2 3 Moderate 26 52 85 do. 11 45 86
1 3 do. 9 28 58 Moderate 1 18 61
Southern 8 3 Trace 6 42 49 race 71 98 100
armyworm 4 3 do. 0 20 46 do. 63 87 99
2 3 Moderate 2 7 26 do. 60 86 94
1 3 do. 0 3 24 do, 16 30 52
Southern beet 8 3 Trace 37 78 86 Trace 10 25 49
webworm 4 3 do. 27 57 75 do. 5 22 C3
2 3 Normal 5 13 31 do. 0 3 19
1 3 do, 2 8 17 Moderate 0 2 10
A limited study was made of the effect of exposure or weathering on deposits of
Q-phenylazoaniline on foliage. For this purpose a spray was made up in proportions
equivalent to 8 pounds of Q-phenylazoaniline and 1/8 pound of saponin to 100 gallons
of water and applied with a knapsack-type sprayer to 12 nearly full grown beet plants
growing in an outdoor garden. A similar plot was treated with an 8-100 derris (4.5
percent rotenone) spray, and a third plot was left unsprayed as a check. When the plants
were dry, six leaf samples (about 2 inches square) were cut at randomi from each plot and
placed in as many Petri dishes for infesting in the laboratory. Five Hawaiian beet
webworm larvae (fifth-instars) were placed in each dish, which was held at room temper-
ature in the laboratory for observation for 72 hours. At the end of 48 and 72 hours
the dishes were examined for mortality of the larvae and an estimate of the feeding on the
leaf sections. Similar samples were cut from the plants and fed to larvae in
the laboratory every 2 days for 10 days. During this period the sprayed plots
were exposed to all weather conditions other than rainfall, from which they
were protected by covering.
The results of these tests (table 3) show that a residue of p-
phenylazoaniline remained effective against the Hawaiian beet webworm for
about 4 days on beet plants but lost its effectiveness thereafter. As the
cDmpound is not very volatile, this loss in effectiveness would seem to have
been caused either by growth of the plant exposing fresh tissue or by a
change in the residue through the action of sunlight or other weathering
factor. Its effectiveness, however, was equal to that of derris, which
caused little mortality after the first 2 or 3 days although causing some
repellency throughout the 10-day period,
Table 3.--Results of tests with leaf samples taken at 2-Cay intervals
from beet plants sprayed in the garden with p-phenylazoaniline and
derris and fed to nearly full grown larvae of the awaiian beet
webworm in Petri dishes
after Kill after -
3 da s 2day_3days
Trace 30 73
do. 63 83
do. 10 40
Moderate 16 33
do. 6 30
do. 0 13
Derris 14.5 5 tenon
after Kill after -
__ds y s 3 days
Trace 43 67
do. 50 73
do. 3 10
Moderate 0 3
do. 6 10
do. 3 10
after Kill after -
3_days__2 days 3days
Normal 0 0
do. 6 6
do. 0 3
do. 0 0
do. 0 0
do. 0 3
A preliminary test of p-phenylazoaniline was made on the American
cockroach by placing 10 nearly full grown nymphs in a 6-inch battery jar on
a disk of paper rather heavily dusted with the pure compound. As the paper
disk covered the entire bottom area of the jar, the nymphs were certain to
come in contact with the powdered chemical. A film of vaseline about the
inside upper edge of the jar prevented the escape of the roaches. The jar
was kept at room temperature in the laboratory. Under these conditions a
deposit of 170 micrograms of dust per square centimeter killed none of the
roaches in 3 days. A slightly heavier deposit of sodium fluoride killed
70 percent of the roaches under the same conditions. p-Phenylazoaniline
was therefore not effective against the American roach, under these condi-
tions at least.
Tests were also made against the cowpea weevil and the rice weevil
to find out the possible use of the compound as a grain protectant. A
variety called Whippoorwill pea was used with the cowpea weevil, and wheat
was used with the rice weevil. The seeds were treated by shaking 15 grams
in a flask with a weighed amount of the insecticide until thoroughly mixed.
The treated grain was then placed in a Petri dish containing 30 adult
weevils and held at room temperature for 3 days. A concentration of 1 part
of p-phenylazoaniline to 1,000 parts by weight of peas caused no mortality
within 3 days, although in a similar test derris killed 100 percent of the
weevils in 2 days. A concentration of I part of p-phenylazoaniline to 200
parts of wheat killed none of the rice weevils within 3 days. Derris, in a
similar test, killed 36 percent of the weevils. It is apparent that 2-
phenylazoaniline is not toxic to these weevils under the conditions of the
The compound was also tested as a soil treatment against termites
by a method described by Hockenyos (4). A weighed quantity of the insecti-
cide, according to the concentration desired, and 40 grams of sandy soil
were ground in a mortar until thoroughly mixed and then poured into a
150-cc. beaker containing about 12 cc. of water and a little tissue paper.
After the dry soil had absorbed the water, 30 adults or large nymphs of the
worker caste were placed in the beaker, which was held for 3 days in a
cabinet at 801F. Under these conditions it was found that a concentration
of 1-200 of the insecticide in soil killed only 50 percent of the termites
in 2 days and a 1-1,000 concentration had practically no effect. Pyrethrum
at 1-200 killed 100 percent of the termites within 48 hours.
p-Phenylazoaniline (p-aminoazobenzene) was tested against 12 species
of leaf-feeding insects in comparison with standard insecticides generally
used with these species. In preliminary tests as a dust on foliage the com-
pound was about as effective as the standard insecticide against the Colorado
potato beetle, the cross-striped cabbage worm, the Hawaiian beet webworm,
and the melonworm. A volatility test showed the compound to be practically
nonvolatile over a period of 5 days, which precludes the possibility of
Spray concentrations of 8, 4. 2. and 1 pound per 100 gallons, with
saponin added as a dispersing agent, were applied to potted plants and
tested against five species of insects confined by screen cages. In these
tests p-phenylazoaniline was equal or superior to the standard insecticide
against the cross-striped cabbage worm, the Hawaiian beet webworm, and the
Spray concentrations of 8 and 4 pounds per 100 gallons applied to
small field plots of tender truck crops caused slight to moderate injury
to swiss chard and pumpkin and little or no injury to bean and collards.
Small field plots of beet plants were sprayed with an 8-100 suspen-
sion of p-phenylazoaniline and leaf samples taken from the plots at 2-day
intervals for a period of 10 days and fed to Hawaiian beet webworms in the
laboratory. The residue was effective for about 4 days but became less
Q-Phenylazoaniline was ineffective against the American roach, the
cowpea weevil, the rice weevil, and termites when tested by the methods
(1) Bushland, Raymond C.
1940. The toxicity of some organic compounds to young screwworms.
Jour. Econ. Ent. 33: 669-676.
(2) Fink, D. E., Smith, L. E., Vivian, D. L., and Claborn, H. V.
1938. Toxicity tests with synthetic organic compounds against
culicine mosquito larvae. U. S. Bur. Ent. and P1. Quar.
Cir. E-425, mimeographed.
(3) Gahan, J. B., Swingle, M. C., and Phillips, A. M.
1941. 1,4-Diphenyl semicarbazide as an insecticide, U. S. Bur.
Ent. and P1. Quar. Cir. E-549, mimeographed
(4) Hockenyos, G. L.
1939. Laboratory evaluation of soil poisons used in termite con-
trol. Jour. Econ. Ent. 32: 147-149.
(5) McAllister, L. C., Jr., and Van Leeuwen, E. R.
1930. Laboratory tests of miscellaneous chemicals against the
codling moth. Jour. Econ. Ent. 23: 907-922.
(6) Swingle, M. C., Phillips, A. M., and Gahan, J. B.
1941. Laboratory testing of natural and synthetic organic sub-
stances as insecticides. Jour. Econ. Ent. 34: 95-99,
(7) Vivian, D. L., and Haller, H. L. J.
1938. Insecticide. U. S. Patent 2,111,879; issued March 22.
UNIVERSITY OF FLORIDA
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