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UNITED STATES DEPARTMENT OF AGRICULTURE

Contribution from the Bureau of Entomology
L. O. HOWARD, Chief

Washington, D. C. PROFESSIONAL PAPER. May 17, 1921

EFFECTS OF NICOTINE SULPHATE AS AN OVICIDE AND
LARVICIDE ON THE CODLING MOTH AND THREE
OTHER INSECTS.

By N. E. McInvoo, Insect Physiologist; F. L. Stuanton,’ Hntomological Assist-
ant; H. K. Prank and R. J. Fisker, Scientific Assistants, Fruit Insect
Investigations.

CONTENTS.
Page. Page.
PntrOGuetiOni = aks s aes ee 1 | Experiments conducted in the labora-
Hxperiments conducted in the labora- tory—Continued.
(HOVC (4, av gern hep sees OS Ker iene ogee, Caren eee 2 Summary of experiments con-
Hffects of nicotine sulphate on ducted in laboratory________ 14
eggs and newly batched larve Experiments conducted in orchards_ 15
of the silkworm moth_______ Pe Experiments performed at Ben-
Effects of nicotine sulphate on LOne ElaTrboOrs = Ninichia ss ase ea 12)
eggs and newly hatched larve Experiments performed at
of the codling moth________ 4 Grand Junction, Colo_______ 16
Hffects of nicotine sulphate on Experiments performed at Ros-
eges of two other insects____ 8 SSA SSE hess Nest SA Stilt eg i RE ance 17
Discussion as to how nicotine Conclusions from field experi-
sulphate acts as an ovicide TOTS ie Ne oe 18
and larvicides 2 a es LO Ue itera tuner citedie. 2 a we ee eee 18
INTRODUCTION.

For several years nicotine and its compounds have been used
against certain soft-bodied insects as contact insecticides, and within
the past few years the question has been raised concerning the effects
of nicotine sulphate upon the eggs and early instars of other insects
‘which are commonly controlled by other means.

During 1915 and 1916, in the State of Washington, De Seliem (4)?
carried on field experiments with nicotine sulphate and arsenate of
lead and claimed that the former insecticide was as efficient as the
latter one for controlling the codling moth (Laspeyresia pomonella
L.). During the season of 1917 similar experiments in three or-
chards were performed by the same author and others (2) on a larger
scale in the same State, and the results obtained showed that nicotine

—

1 Resigned March 31, 1920.
2 Numbers (italic) in parentheses refer to “‘ Literature cited,” p. 18.

22660°—21—Bull. 988—1

2 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

sulphate did not control the codling moth as well as did lead arsenate,
and that its control was unsatisfactory on all of the plats sprayed,
except one. The Bureau of Entomology also conducted some field
experiments during the season of 1917 in three important apple
regions in the United States, the first of these being in the Lake region
at Benton Harbor, Mich.; the second one in the mountainous region
at Grand Junction, Colo.; and the third one in the semiarid region
at Roswell, N. Mex. In the first region the experiments were carried
on by Mr. Simanton; in the second one by Mr. Plank; and in the
third one by Mr. Fiske. All of the laboratory experiments were per-
formed by Dr. McIndoo.

Lovett (4) reports that nicotine sulphate with soap is an effective
ovicide for the codling moth. Excepting this experiment, in which
only 26 codling-moth eggs were used, no other experiments, either in
orchards or in a laboratory, have ever been conducted to determine
how nicotine sulphate checks the work of the codling moth, although
Feytaud (3), testing the effects of pure nicotine and soap in the labo-
ratory upon the eggs of two moths belonging to the same family,
ascertained that about 75 per cent of the embryos in the eggs tested
were aborted during the last stage of development, while the remain-
ing eggs hatched.

The first portion of the present paper embodies the results obtained
in the laboratory concerning the effects of nicotine sulphate as an
ovicide and larvicide on the codling moth and three other insects.
The second portion of this study deals with the effectiveness of nico-
tine sulphate as compared with the efficiency of arsenate of lead for
controlling the codling moth in orchards.

EXPERIMENTS CONDUCTED IN THE LABORATORY.

In order to throw some light on how nicotine sulphate checks the
work of the codling moth the following tests were performed :
EFFECTS OF NICOTINE SULPHATE* ON EGGS AND NEWLY HATCHED LARV OF

THE SILKWORM MOTH.

This investigation was begun in September, 1916, when it was too
late to obtain codling-moth eggs or fresh eggs of any other insect;
so the study was begun by using eggs of the silkworm moth (Lombyx
mori L.), 10,000 of which were 14 months old, 2,000 of which were
from 1 to 6 days old, and 10,000 of which were 3 months old.

EFFECTS OF NICOTINE SULPHATE ON EGGS OF THE SILKWORM MOTH.

The eggs just enumerated were divided into several lots, and some
of these lots were sprayed with nicotine sulphate (1:800 -+ fish-oil

’'Throughout this paper reference is made to “nicotine sulphate” containing 40 per
cent of nicotine.

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 3

soap, 2 pounds to 100 gallons of water) ; some with nicotine sulphate
1: 800; some with nicotine sulphate 1:1,066; and others were not
sprayed, these being used as controls. During October, 1916, all of
the eggs 14 months old hatched, but the hatching of the sprayed ones
was more or less retarded. Relative to the eggs from 1 to 6 days old
when treated, the following data were obtained during the spring of
1917. Only 1 per cent of those sprayed with nicotine sulphate
1:800 hatched, while 80 per cent of the unsprayed ones hatched; in
regard to the eggs 3 months old, 20 per cent of those sprayed with
nicotine sulphate 1:800-++soap hatched, 25 per cent of those sprayed
with nicotine sulphate 1: 800 hatched; 35 per cent of those sprayed
with nicotine sulphate 1: 1,066 hatched; while 90 per cent of those
unsprayed hatched. The unsprayed eggs hatched quickly, and the
newly hatched larve grew normally, while the sprayed eggs were
more or less retarded in hatching and the young larve were so
stunted that after 20 days the larvee from the unsprayed eggs were
from 1 to 6 times as large as those from the sprayed eggs. A large
percentage of the unhatched eggs contained embryos aborted during
the last stage of development.

EFFECTS OF NICOTINE ON NEWLY HATCHED SILKWORMS. ~

McIndoo (6, p. 97) has already shown that the exhalation (called
odor) from leaves an hour after having been sprayed with a solution
of nicotine sulphate kills small fall webworms (Yyphantria cunea
Dru.), small caterpillars of the catalpa sphinx (Ceratomia catalpae
Bdv.), and certain aphids (Aphis populifoliae Davis).

On May 12 at 12.30 p. m. a bunch of leaves on a mulberry tree was
dipped into a solution of nicotine sulphate 1:400 and another bunch
into a solution 1:800. On May 14 at 9.30 a. m. a leaf was removed
from each bunch of the leaves treated, and 20 silkworms 1 day old
were placed on each leaf; at 12.30 p. m. all the worms were dead.
The leaves still emitted a faint odor like that from the solution.
On May 16 at 11.15 a. m. the preceding experiment was repeated;
on May 17 at 9 a. m. 8 worms on the leaf treated with the solution
1:400 and 1 on the other leaf were dead; all of the remaining live
worms were more or less stupid, and two hours later, after having
been fed with a fresh leaf treated with the solution 1:400, died.
This leaf was cut into small pieces, and it still emitted a very faint
odor like that from the solution, but the leaves treated with the
solution 1:800 had ceased to emit this odor so far as the observer
could perceive. At no time during any of the preceding experiments
did the silkworms eat the treated leaves; the exhalation arising from
them therefore must have killed the worms.

4 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

EFFECTS OF NICOTINE SULPHATE ON EGGS AND NEWLY HATCHED LARVZ OF
THE CODLING MOTH.

In tests with the eggs and newly hatched larve of the silkworm
moth it was determined that nicotine sulphate is efficient against
only the fresh eggs, but more or less retards the hatching of older
egos. The exhalation from leaves which had been dipped into solu-
tions of nicotine sulphate from 1 to 5 days previously killed newly
hatched silkworms, and from the sixth to the eleventh day after
the foliage had been treated the newly hatched silkworms, after
having eaten some of these treated leaves, died, the mortality varying
from a high percentage on the sixth day to no mortality on the tenth
and eleventh days. The following pages give the results obtained
by using the eggs and newly hatched larve of the codling moth:

EFFECTS OF NICOTINE SULPHATE ON EGGS OF THE CODLING MOTH IN THE
LABORATORY.

Many codling-moth sticks containing wintering larvae, reared at the
bureau’s field station in Grand Junction, Colo., were shipped to
Washington, D. C., where they were kept out of doors until March 1,
1917; after this date they were kept in a refrigerator, and at irregular
periods about 40 of them at a time were removed from the refrig-
erator and were placed in battery jars, which were covered with
cheesecloth. Each morning the moths that had emerged were re-
moved to other battery jars containing moist sand and either glass
plates or foliage of fruit trees. In these jars the moths copulated
and the females laid their eggs on the glass plates and foliage, which
after being removed were then sprayed. By this method eggs of a
known age were easily obtained.

Since these experiments were started in March, when fruit-tree
foliage was not to be had, glass plates were put in the battery jars,
and whenever a sufficient number of eggs had been deposited on these
plates, the latter were removed, sprayed, and then placed in other
battery jars also containing moist sand.

Since the details of the four experiments performed, using eggs on
glass plates, are similar, only Experiment No. 1 will be described
fully. On April 4 the first plate, bearing 57 eggs (1 and 2 days
old), was sprayed with a solution of nicotine sulphate 1:400; the
second plate, bearing 20 eggs, with a solution 1:800; and a third
plate, bearing 16 eggs, was used as a control. Each plate was put
in a separate battery jar. On April 7 most of the eggs were in the
red-ring stage; the sprayed plates bore spots or a thin film as a.
residue left after the evaporation of the solution, and these spots
still emitted a nicotine-like odor. On April 11 many of the eggs
were in the black-spot stage and the plates still emitted the nicotine-
like odor; two small last year’s apples were put in each jar. On

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 5

April 12 the eggs on each plate began to hatch, and later when
examined 42.1 per cent of those on the first plate had hatched; 60
per cent of those on the second plate and 92.7 per cent of those not
sprayed had hatched. On April 13 several dead larve were found
on the sprayed plates and on the apples by these plates, but no dead
ones were found in the jar containing the control plate, and four bur-
rows were counted in the apple by this plate. On later dates it was
common to see dead larve in each of the first two jars. On April 23
the plate sprayed with the solution 1:400 still emitted a faint nico-
tine-like odor. The apples by this plate showed four burrows, from
which finally emerged two full-grown larve; those by the other
sprayed plate only one burrow, from which emerged a larva; and
those by the control plate also four burrows, from which emerged
two large larve. Four of the five larve passed through the pupal -
stage and emerged as adult moths, while the fifth one only reached
the pupal stage; this one was from the first two apples mentioned.

The preceding tests indicate that nicotine sulphate is not an effi-
cient ovicide against the codling moth when the eggs are laid on glass
plates. Other experiments were performed by constantly keeping
fresh foliage of pear and apple trees in the battery jars. On the
third day after applying the spray solution a nicotine-like odor was
still emitted from the leaves, the strength of which depended upon
the strength of the solution used. This odor gradually disappeared,
and by the time the eggs began to hatch the observer could not per-
ceive it. Unsprayed leaves usually have bright and shiny surfaces,
but sprayed ones have dull surfaces, and with the aid of a hand
lens a dried film of residue from the solution may often be seen on
them. These experiments are summarized in Table I; experiments
1, 2, and 3 represent individual tests with eggs on pear-tree leaves,
while experiment 4 is a summary of several tests with eggs on apple-
tree leaves. Soap was used at the rate of 2 pounds per 100 gallons
of water.

Relative to experiment 4, the following notes, although not signifi-
cant, are nevertheless interesting. Four last year’s apples, each be-
ing dipped into the same spray solution as that sprayed on the leaves,
were placed in four jars containing the sprayed leaves. Two apples
not sprayed were also placed in two jars containing unsprayed
leaves. Eliminating one of the four jars and its contents on account
of the apple in 1t becoming badly decayed before the eggs hatched,
245 eggs in the other three jars hatched and later 14 burrows were
counted in the three remaining apples. In the two jars used as
controls 52 eggs hatched, and later 14 burrows were also counted in
the two apples contained therein. Soon after this date all of these
apples totally decayed and consequently no matured larve were ob-
tained from them.

6 BULLETIN 9388, U. S. DEPARTMENT OF AGRICULTURE.

Three apples, after having been dipped into a solution of nicotine
sulphate 1:400-++soap, were placed in three battery jars containing
many unsprayed eggs. <A later examination showed that 49 eggs
had been deposited on the apples, 47 of which had hatched. These
decayed apples contained 39 burrows, and finally two moths were
found in each of two jars. A repetition of this experiment resulted

in obtaining no moths from three dipped apples and only two from

three control apples.

TABLE 1.—ZEffects of nicotine sulphate on codling-moth eggs (1 and 2 days old)
laid on fruit-tree foliage in laboratory.

BER! : Number Eggs
Bieia bra = Strength of nicotine-sulphate solution Eggs atin HA totally
Experiment No. | used, and control. ot ees hatched. | aborted. | unde-
iis veloped.
| Per cent. | Per cent. | Per cent.
AQ eereitaira 2a pee td Mieenee Merman 15 53. 3 AGT Nowa
1 if SOQ? cee Z Tait OF Sterey: eS 33 66. 7 Ss Lae Sas
CS ah a par en ar IE 800-CSOADE +2 a. = sa eeeesans-ceeeeqese = 15 EB ie Sear ease 36.3
Gontrol?s. 3:22 2336. ee es 29 GGG [see ES 3.4
9 it sEQO0--SOap- 2 Epi PE Se se ELECE ES 38 92.1 AG BIS
ats Gata Ae ee COntrOl nee Bese etas Tee cis veers rl 79 OS Fialte tee se 1.3
: DOOR MM sn. oematinary, taney ee eo 52 63.5 13.4 23.1
Fy GO nage a ra h\Controly. 5 =. fo) - SSE eee || 64 95.3 3.1 1.6
PAQOKE CE Lae. Sf eeR Fas SS ee Eee. eel THUS 47.4 52.6 | oh eee
4 | 1400" "Soapiate. ses ee sl ae. oS oes | 158 49, 2 47,4 | 3.4
LIT Siii Rea fF @W0+-soapss- (3-2 2255.08. Auld ag 213 79. 8 MZ. LEAS
(Control Be ie eee sete reer 36 | 94.4 Brean ee 5.6

To test the value of nicotine sulphate as an ovicide for codling-
moth eggs, two experiments were started by EK. H. Siegler, ento-
mological assistant, June 5, 1918, at the bureau’s field laboratory in
Wallingford, Conn. In each experiment the eggs were deposited
on apple-tree foliage by moths confined in oviposition jars. All of
the treated eggs were thoroughly immersed in a solution of nicotine
sulphate 1:800 plus common laundry soap (3 pounds to 50 gallons
of water). After treatment each leaf was placed in a separate jar,
with an apple as food for the larve as they hatched.

Experiment No. 1—In this experiment the eggs were deposited
June 3, and at the time of dipping them into the spray solution many
had advanced to the red-ring stage. Seven leaves bearing 310 eggs
were treated, while one leaf bearing 190 eggs was left untreated
as a check. The results obtained show that out of 310 eggs treated,
296, or 95.48 per cent, hatched; out of 190 untreated eggs 96.84 per
oa hatched. Many oh the re entered the apples a commenced
feeding vigorously therein.

Experiment No. 2.—The eggs i ae in this test were deposited
June 4, and at the time of dipping them into the nicotine-soap solu-
tion none had advanced to the red-ring stage. Out of a total of 37

eggs, 35, or 94.59 per cent, hatched; out of 11 untreated eggs, 11, or

_ as ea eee

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. vé

100 per cent, hatched. As in experiment No. 1, many of the newly
hatched larve entered the apples and started their development
therein.

EFFECTS OF NICOTINE SULPHATE ON NEWLY HATCHED LARVA OF THE CODLING
MOTH IN THE LABORATORY.

From the preceding results it is evident that nicotine sulphate is
not an efficient ovicide against the codling moth; and since the eggs
probably hatched after the cessation of an injurious exhalation from
the sprayed glass plate and leaves, the newly hatched larve perhaps
died of starvation, rather than from the spraying. . To test the effects
of the exhalation from leaves sprayed one or more days previously
upon the newly hatched larve, the following experiments were
performed :

At 11.30 a. m. a pear-tree leaf was dipped into a solution of
nicotine sulphate 1: 400, and another one into a solution 1: 800. At
1.30 p. m., when the leaves were dry, 15 newly hatched codling-moth
larvee were placed upon each leaf. At 4.30 p. m. 13 larvee were dead
on the first leaf, but only 6 dead on the second leaf. The leaves still
emitted a nicotine-like odor. The following morning all the larve
were dead and the leaves were wilted. At no time did any of them
try to burrow into the leaves as do larvee on leaves not treated with
these solutions, and they crawled away from these leaves more than
do larvee on untreated leaves.

On May 4 a twig bearing foliage on an apple tree was dipped into
a solution of nicotine sulphate 1: 400, and another twig into a solu-
tion of 1: 800. On May 14 a leaf was removed from each twig and
then 28 newly hatched codling-moth larve were placed upon each
leaf between two watch glasses. During the first day the larve
burrowed considerably in the leaves and apparently were not affected.
During the second day three of them died, but the leaves began to
wilt. During the third day all of them died, and by this time the
- Jeaves had become dry. Between May 4 and 14 there had been much
rain and on the latter date the leaves did not emit a nicotine-like
odor. This experiment shows that the exhalation from the treated
leaves did not affect the larvee and that in all probability all of them
finally died of starvation.

On May 18 the two twigs mentioned in the foregoing paragraph
were again dipped into solutions of the same strengths, but this time
soap was added at the rate of 2 pounds per 100 gallons of water.
On May 19 six newly hatched larve were placed on each of two
detached leaves as usual. The leaves still emitted a faint odor
resembling that from the solutions. No larve died that day and
only 4 of the 12 were found dead the following saan The leaves were
shghtly eaten.

8 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

On May 20, at 1 p. m., or the second day after the leaves had been
treated, 13 codling-moth larvee were placed on each of two detached
leaves; at 3 o’clock 6 silkworms (2 days old) were also placed on
each leaf; at 4.30 o’clock 10 of the 12 silkworms were dead, but not
one of the codling-moth larve had succumbed. The following morn-
ing all of the silkworms were dead, but only 12 of the 26 codling-
moth larvee had succumbed. The leaves were slightly eaten.

On the third day after the leaves had been treated the preceding ex-

periments were repeated. On this date only a few of the silkworms
and none of the codling-moth larve died. The following morning
all of the silkworms were dead, but the codling-moth larve did not
die til] later, when the leaves began to dry.

On the tenth day after the leaves had been treated the codling-
moth larvee tested apparently were not affected.

On various dates many smali pears (22 mm. in diameter) with the
calyx cups yet open were picked and then sprayed with solutions of
nicotine sulphate. Some of these solutions contained soap in the
proportion of 2 pounds to 100 gallons of water. The stem of each
pear used was inserted into a small bottle containing water. From
one to seven days after the pears had been sprayed six active codling-
moth larve were removed from the oviposition jars and then placed
on each pear; unsprayed pears were used as controls.

A glance at Table IT shows that about 75 per cent of the larve
tested were killed when placed upon pears which had been sprayed
one or two days previously. It is also seen that the mortality de-
creases to about 25 per cent on the sixth and seventh days.

Taste I].—F#ffects on newly hatched codling-moth larve when placed upon
small pears previously sprayed with solutions of nicotine sulphate in labora-
tory.

|

7 - ; e : : , Solution Solution
Ee Solution 1:400 | Solution 1:800. 1:400-+soap. 1:800--soap. Control.
after ; a
spraying | | |
ee Num- | Larve | Num-| Larve | Num-| Larve | Num-| Larve | Num-| Larve
eae berofj| found ber of} found berof} found ber of} found ber of| found
Waite larve | dead on | larve | dead on |} larve | dead on | larve |} dead on | larve | dead on
tested tested.| pears. |tested.| pears. |tested.| pears. | tested.| pears. | tested.| pears.
| | | |
Per cent. Per cent Per cent. Per cent. | Per cent.
ee oe ee 18 (242 18 Uke eck Soe bed = See ere Se Ga ees eee 18 | 0.0
DONE Lin Se 18 7 Aa 18 Wana 18 61.1 12 25. 0 6 | 16.6
Sh Ave y iy [eee epee Aap lel lee ee Secu 6 100. 0 6 6636 ecco. Sie
7 ae ee eas Wel 6 50. 0 6 50. 0 | 6 50. 0 6 B3I3 122 ee ee ee
at ee @ eel ae 6 83. 3 6 66.6 | 6 BS Bere te] eer ce 6 16.6
Goa eee 12 25. 0 6 33. 3 | Sood pcb Bac ce blea coe nck oeecceeaneteet c aee Cae ae
Ce rs: 6 BBAS 6 33. 3 |

EFFECTS OF NICOTINE SULPHATE ON EGGS OF TWO OTHER INSECTS.

Experiments similar to those performed on the eggs of silkworm
moths and codling moths were also conducted upon the eggs of

os ae

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 9

potato beetles (Leptinotarsa decemlineata L.) and tussock moths
(Hemerocampa leucostigma S. & A.).

Fifteen potato-plant leaves, each bearing a cluster of potato-
beetle eggs (1 and 2 days old), were collected in a potato patch, and
after the petiole of each leaf had been inserted into a bottle of water
in the laboratory, 11 of the leaves were sprayed with solutions of
nicotine sulphate 1:400 and 1:800 and the other four leaves were
used as controls. The eggs thereafter were observed daily; prac-
tically all of them hatched, and the newly hatched larve were ap-
parently not affected by remaining on the wilted leaves 1 or 2 days,
after which they thrived when fed fresh and unsprayed leaves. Rela-
tive to the time of hatching there seemed to be little, if any, differ-
ence between the sprayed and unsprayed eggs. Similar results were
obtained by spraying eight clusters of potato-beetle eggs in a potato
patch with a solution 1:400 containing soap (2 pounds to 100 gallons
water).

In order to obtain tussock-moth eggs of known ages, many large
caterpillars of this moth were collected and were put in wire-screen
cages, in which the remainder of the life history was completed. On
various dates eggs from these cages and some from trees in the field
were collected, placed in open pasteboard boxes, and then sprayed
with four solutions of nicotine sulphate. Two of the solutions con-
tained soap in the proportion of 2 pounds per 100 gallons of water.
Some oi the control eggs were not sprayed, while the others were
sprayed with tap water; no difference in hatching between these was
observed. The details of these experiments are summarized in
Table HT:

TasLe I11.—Lffects of nicotine sulphate on eggs of tussock moth in laboratory.

Eggs collected in cages. Eggs collected in field. Age
probably from freshty-

laid eggs to these ready to
Strength of Eggs 1 and 2 days old. Eggs 2 and 3 days old. hatch.
nicotine-
sulphate z
solution i ea Pate |
used, and Num- Egg Egg Num- | Egg Egg Nuim- Se Egg
control. ber of | snasses | masses | berof; J occeq | Masses | berof| jj occag | es
S| that that | ©gg | that that | ess | that that
masses | notched. | did not | masses| p¢chea,| did not | masses] yt chéa | did not
tested. *| hatch. | tested. -| hatch. | tested. | : hatch
|
e $$ }
Per cent. | Per cent. Per cent. | Per cent. Per cent. | Pe cent.
Rees Caer Se eee 4 25. 0 75.0 12 83. 3 15.7
JESU a eee aaa peleiess ES SO Ree eG. ee cea k See 4 62. 5 IOs Waetecaeee= ee ae ees ere eee
1:800+soap...-.- | 4 25. 0 75.0 4 25.0 75.0 33 87.9 121
1:1000+soap. ---- 4 37.5 625 See heen ee eee | eee ae 45 82. 2 17.8
Cit. 20] 3 83. 4 16.6 4 | 87.5 1255 45 93.3 6.7

It is seen from Table III that nicotine sulphate is not efficient
against the eggs of the tussock moth; the percentages given for the
masses of eggs that did not hatch, however, are too low, because the
_ final examination showed that as a rule when a control and a sprayed
22660°—2i—Bull. 98388——2

10 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

mass of eggs (both recorded as hatched) were closely observed, more
larvee had emerged from the former than from the latter. The ones
sprayed with nicotine sulphate were slightly retarded in hatching,
and the eggs in most of the masses which did not hatch contained
aborted embryos, while the remainder of them were totally unde-
veloped.

DISCUSSION AS TO HOW NICOTINE SULPHATE ACTS AS AN OVICIDE AND
LARVICIDE.

It is difficult to determine accurately how any insecticide kills a
larva or an adult insect, and in the light of our present knowledge
along this line it would perhaps be impossible to ascertain definitely
how an ovicide affects insect eggs. For this reason no attempt was
made in the present investigation to determine how nicotine sulphate
killed the eggs tested. Nevertheless a little theory on this subject
may not be out of place here.

Before attempting to explain how nicotine sulphate acts as an

ovicide, it is first necessary to know something about the coverings of

an insect egg. It is well known, as compiled by Packard (8, p. 520),
that a ripe insect egg has two coverings. The external one, the ege-
shell or chorion, is usually thick and hard; it is pierced by one or
more minute canals, the micropyles, and consists of two chitinous-
like laminee kept in close apposition by means of numerous minute
pillars. The internal covering, the vitellne membrane, is always
thin and delicate. The developing embryo inside the egg is supposed
to breathe directly through these coverings as does a chick embryo
through the shell of a hen’s egg.

According to the results already presented, it was ascertained that
freshly laid eggs, sprayed with solutions of nicotine sulphate, were
affected more than were older eggs likewise treated. The chorions
of these eggs were not as hard as those of the older eggs. This fact
alone may explain the difference in the mortality recorded. Since it
is scarcely possible that the spray solutions passed through the egg-
shells, there remain two possible methods of explaining the death of
the eggs sprayed: (1) Upon evaporation of the spray solutions there
was usually left a thin film on the leaves sprayed, and perhaps also
on the eggs. This film on the eggs might have decreased the aeration
through the eggshells and thus caused death by suffocation. (2)
Since practically all of the aborted embryos appeared to have died
during the last stage of development, the preceding view does not
seem to have much weight. As the sprayed surfaces continued to emit
a nicotine-like odor for some time after the spray solutions had been
applied, it seems reasonable to suppose that the embryos were killed
by breathing the exhalation from the sprayed surfaces through the
egeshells. Nicotine is a nerve poison, and the more highly developed

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 11

the nervous system the more effective the poison. This fact probably
explains why practically all of the embryos that died succumbed
during the last stage of development.

Feytaud (3) described five stages in the embryology of (Hudemis)
Polychrosis botrana Schiff. and of (Phalonia) Conchylis ambiguella
Hbn., and he treated many eggs of these moths with various strengths
of pure nicotine and soap. The resulting mortality varied consider-
ably, but even the strongest solution (1: 666) used did not prove effi-
cient. He tested the eggs in the various stages of development, but
in almost every case in which the embryos died they succumbed dur-
ing the last stage. i

Lovett (4) sprayed apple-tree foliage with solutions of nicotine
sulphate, and after several hours, when the leaves were perfectly dry,
he placed many small tent caterpillars (Malacosoma pluvialis
Stretch) on these leaves. He states that these caterpillars showed a
decided aversion for the sprayed leaves; all of them soon became sick
and a large percentage of them died. On the third day after the
fohage had been sprayed more caterpillars were placed on the same
leaves and similar results were obtained. The leaves were not eaten.
Lovett performed other experiments in which the caterpillars slightly
ate the leaves which had been sprayed several hours previously. In
this case the action of the nicotine was quick and decisive. These
results agree with those given in the preceding pages.

Theoretically nicotine sulphate is nonvolatile, although we know
from experience that the commercial 40 per cent nicotine sulphate
(the kind used in all the preceding experiments) is more or less
volatile. Moore and Graham (7) state that pure nicotine sulphate is
nonvolatile, and demonstrated that its vapor or exhalation (if either
one is given off) did not kill the insects tested. They also state
that commercial 40 per cent nicotine sulphate contains from 1 to 2
per cent of free nicotine, whose vapor did kill the insects tested.
Moore and Graham claim that when spray solutions are prepared
by using commercial nicotine sulphate, hard water, and soap, the
nicotine sulphate is decomposed, setting free the nicotine; the amount
of decomposition depends upon the amount of alkalies contained in
the solutions. This view easily explains the presence of a thin film
(already mentioned several times) left upon evaporation of the
spray solution, which is certainly the nonvolatile portion of the
nicotine sulphate contained in the solution. For some time after
the application of the solution the film continues to emit an odor
and its exhalation is more or less toxic to young larve, showing
that it 1s not pure nicotine sulphate according to Moore and Graham.

Moore and Graham (7) state that 12 days after lettuce in a green-
house had been sprayed with a solution of commercial 40 per cent
nicotine sulphate, it still bore nicotine.

12 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

To determine how long nicotine sulphate may remain on fruit-tree
foliage after the application of the spray solution, the following ex-

periments were performed by McIndoo. On September 10 a small

pear tree was sprayed with a solution of commercial 40 per cent
nicotine sulphate 1: 800, containing fish-oil soap (2 pounds to 100
gallons water). On various days thereafter about a quart of the
sprayed leaves were collected on each recorded date; the leaves, after

being ground in a meat grinder, were then mixed thoroughly with

water containing sodium carbonate. Upon distilling this mixture a
distillate containing nicotine was obtained on each day tested up to
the thirty-fifth day after the leaves had been sprayed. On the forty-
second day after applying the spray solution only an indication of a
precipitate was observed, but concluding from the precipitates ob-
tained prior to this date the amounts of nicotine present in the
distillates seemed to decrease irregularly from the first to the forty-
second day ; soon after which the remaining leaves fell from the trees.
During these tests there was comparatively little rainfall; neverthe-
less the results of the tests indicate that considerable rainfall is
required to remove all of the nicotine sulphate adhering to the sprayed
leaves. The details of these tests are presented in Table IV:

TABLE IV.—Tests on various dates using pear-tree leaves which had been

sprayed on Sept. 10 with a solution of commercial 40 per cent nicotine sul-
phate (1: 800) containing soap to show the presence of nicotine.

| Kind of precipitate

Number obtained using—
ores Amount
Date. fences a _of Remarks.
Hadinean Phospho- Silico- rainfall.
Sparen molybdic | tungstic
SOE ee: acid. acid.
Inches
Sept. 11 1 | Heavy ...-| Heavy..-- 0.00 | Sprayed leaves emit nicotinelike odor.
Sept. 12 DRG a. 2 eC Oeeeeeee . 00 Do.
Sept. 12 @) None}. UNone==o5-- .00 | Unsprayed leaves on another tree were used.
Sept. 13 3 | Heavy..--| Heavy...- .00 | Sprayed leaves do not emit nicotinelike odor.
Sept. 14 A PLO see do.. .14
Sept. 15 DER ee. <sice close eeerarene -O1
Sept. 16 Ogee eae | SR . 08
Sept. 18 Suen eee Hainteense - 00
Sept. 24 14 do Very faint Ab
Sept. 27 (eC ees le eee ee -07
Sept. 28 aU] Lae eh eS cee) (Pe aie ene ee a6
Octal 21 | Fair Very faint 00
Occitan 4 NE ae nee See eee apne 01
OGin % Oe etee ee erate | chee em. atte 20
Oct. 8 28 | Fair... None 07
Oct. 9 DAS) | tes ek Sos aan sO (dea § Spd Se 35
Oct: il STN Sade She a See eeeee see tetse 01
Oct. 12 SPH Net ee seg aoe le eg ae 36
Oct 415 35 | Very faint.} None... 1
Oct. 19 SON es samesc re bacces oootte 89
Oct. 20 ON Rabe Se eeoae| Pe aeemere me ol
Oct. 22 AON InGicawon=|\"NOMOsssss}nee=-seeee
Total amount ofrainfall during tests. - . 2. 36
1 Control.

yo allie

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. ¥3

At the suggestion of Mr. V. I. Safro, McIndoo washed separately
50 sprayed pear-tree leaves in 50 cc. of water. The resulting filtrate
was acidified with hydrochloric acid and then tested for the presence
of nicotine by adding phosphomolybdic acid and silicotungstic acid.
Each test apparently showed the presence of nicotine. Fifty un-
sprayed leaves were likewise tested as a control; no precipitate was
observed. One hundred unsprayed leaves were also tested, using the
same amount of water; this time a precipitate was observed, and the
same result was obtained thereafter on several occasions. Only green
and unbroken leaves were used in these tests. At all times there is
more or less foreign organic matter in the form of dust on the leaves;
this is readily seen in microscopical sections through unsprayed
leaves, and alkaloidal reagents precipitate it, as well as the nicotine
which may be present. Consequently the preceding method should
not be regarded as reliable; nevertheless, Mr. Safro (9) has pub-
lished his method and says:

Generally we are able to obtain a definite indication of the presence of nico-
tine in as little as 25 ce. of water by using five leaves that had been sprayed
at the usual strength (about 0.05 of 1 per cent nicotine).

On the fourth day after the pear tree used in the experiments had
been sprayed, about a quart of the sprayed leaves were collected and
washed in water containing sodium carbonate, each leaf being washed
separately. Next the leaves were washed in running water for 5
minutes, and were finally ground and tested as described above. By
adding phosphomolybdic acid to the resulting distillate, a faint pre-
cipitate was obtained, but none by adding silicotungstic acid. On
the eighth day after the leaves had been sprayed, the test was re-
peated, but this time the leaves were washed for 10 minutes in running
water. No precipitate was observed in this test even by adding
phosphomolybdic acid. In each of the two foregoing tests the water
containing the sodium carbonate and foreign matter removed from
the leaves was distilled. Adding either acid to the resulting distillate
invariably produced a precipitate, but in none of the tests with
sprayed leaves did the distillate ever emit a nicotine odor. The
second experiment described above indicates either that the spray
solution did not pass into the leaves or that the amount of nicotine
still held by them was too small to be detected by the method em-
ployed. The following results will substantiate the former view:

A small quantity of nicotine-sulphate solution (1:800) containing
fish-oil soap (2 pounds to 100 gallons of water) was colored with car-
mine acid (Griibler’s Carminsaur) and an equal quantity with
indigo carmine (sodium sulphindigotate). Several leaves on a pear
tree were sprayed with each of the colored solutions, and two entire
detached leaves were submerged in each solution for 15 minutes; the

14 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

petioles of the leaves were left projecting above the surfaces of the
solution. An hour later the four treated leaves were put into absolute
alcohol and a day later a few of the stained leaves on the tree were
hkewise treated. The absolute alcohol did not dissolve or scatter
either one of the stains, and the only other reagents used were xylol
and Canada balsam; these also did not scatter the stains. A study of
the sections made shows much stain on the outside of the sprayed
and submerged leaves. While none was observed inside the sprayed
leaves, it was usually present inside the submerged ones and the most
of it seems to have passed through the ventral surfaces of the leaves.
Its passage may have been aided by the stomata which occur exclu-
sively on the ventral surface of these leaves; botanists, however, say
that the stomata are so small (0.0006 mm. and less) that neither dust
nor water can pass through them into the plant. According to the
above results the spray solutions did not pass into the leaves sprayed,
nor did the dust in the film of adhering nicotine sulphate enter the
stomata.

SUMMARY OF EXPERIMENTS CONDUCTED IN LABORATORY.

Nicotine sulphate as an ovicide, with one exception, was found
inefficient against all of the eggs tested—namely, those of the silk-
worm moth, codling moth, tussock moth, and potato beetle. The
eggs sprayed with it were variously affected, depending on the
strength of the spray solution used, on the age of the eggs tested,
and whether or not the solution contained soap. Upon the eggs of
three of the species of insects used there was practically no differ-
ence in effects between solutions containing soap and those without
soap, although those with soap were much more effective upon the
eges of the tussock moth. Comparing the effects of the spray solu-
tion 1:800, the strongest one of the economic solutions used, the
percentages of eggs sprayed with it that failed to hatch are as fol-
lows: Ninety-nine per cent of the freshly laid eggs of the silkworm
moth, but only about 75 per cent of the older eggs of the same
insect; about 20 per cent of the codling-moth eggs on apple-tree
foliage; 75 per cent of the tussock-moth eggs (1 to 3 days old) ; and
about 12 per cent of those of the same insect which had been col-
lected in the field; and practically none of the potato-beetle eggs.

The effects of the exhalation from leaves sprayed with solutions
of nicotine sulphate varied considerably, depending on the larve
tested and the strength of the solutions used. Again comparing the
effects of the solution 1: 800, all of the newly hatched silkworms and
codling-moth larve placed upon leaves sprayed two hours previously
died, but the silkworms succumbed the more quickly; all of the silk-
worms but only a small percentage of the codling-moth larve placed
upon leaves sprayed 24 hours previously died.

ee ed ee

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 15

Seventy-seven per cent of the newly hatched codling-moth larve

placed upon pears sprayed 24 hours previously with a solution of
nicotine sulphate 1:800 died, but only 33 per cent of those placed
upon pears sprayed a week previously died.
_ Relative to the control of the codling moth, the following briefly
summarizes the more important points herein recorded: About 20
per cent of the freshly laid eggs sprayed with a solution of nicotine
sulphate 1: 800 failed to hatch, and one-third of the remaining em-
bryos that emerged died before they entered pears sprayed a week
previously. Hence about one-half of the eggs and larvee had been
destroyed up to the time when the remaining larve entered the
sprayed pears; a large percentage of the latter larve died, as about
60 per cent of the pears did not become wormy. According to these
laboratory results nicotine sulphate does not seem to be efficient
against the codling moth, although only one application of it was
made; nevertheless its effectiveness would certainly be increased
in proportion to the number of its applications and to the amount
of rainfall.

EXPERIMENTS CONDUCTED IN ORCHARDS. -

According to the preceding laboratory results nicotine sulphate
would not seem to be efficient against the coding moth. To deter-
mine this from the practical viewpoint the following experiments
were conducted :

EXPERIMENTS PERFORMED AT BENTON HARBOR, MICH.

The experimental work conducted at Benton Harbor consisted in
testing the relative efficiency of nicotine sulphate when combined
with soap and when combined with soap and arsenate of lead in
contrast with the efficiency of arsenate of lead when combined with
lhme-sulphur at summer strength. The experiments were made in a
sod orchard about 50 years old, and each of the four plats selected
consisted of 16 trees. :

All of the applications throughout the season were made with the
same power sprayer and at a pressure well above 100 pounds. The
spray was delivered through the Vermorel type of nozzle. Although
the experiments were started with the calyx application, all of the
plats, including the check (No. 4), were given the cluster bud
application.

The set of fruit was scattered and rather light, being lightest in
plat No. 3, but it was sufficient to give reliable experimental results.
In order that trees with as uniform a crop as possible might be
secured throughout the different plats, five count trees in each plat
were not selected until after the fruit had set. The fallen fruit was

16 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

collected once a week and examined for codling-moth injury, and
at picking time the picked fruit was also examined. The results of
these examinations are given in Table V.

TABLE V.—Codling moth injury as shown by examination of both fallen and
picked fruit from experimental plats at Benton Harbor, Mich., 1917.

Fruit record.
No 2 ioe : (ose. Percent-
er Number of applications and brief | Number of larval en- Total age of
rat formula of each. trances at— Number | number | otal
pi. of wormy | of apples} number
| apples. | exam- | of apples
ined. | free from
| Calyx. Side. | Stem. 1 worms.
|
1 | 1 application of lime-sulphur and 3 |

applications of lime-sulphur + 1
pound arsenate of lead to 50 gallons

2 | 1 application of lime-sulphur and 3
applications of nicotine sulphate |
BE LS Sr a Segre Getty 559 662 ral 1,249| 9,924 87. 41
3 | 1 application of lime-sulphur and 3 |
| applications of nicotine sulphate |
| 1:800+soap+0.5 pound of arsenate | |
| oflead to 50 gallons of water... _....- 49 195 4 2
4 | 1 application of lime-sulphur (check). _| 2,032 607 93 2,4

|

Reference to Table V shows that nicotine sulphate (plat No. 2)
gave a control of only 87.41 per cent, while arsenate of lead (plat
No. 1) gave a control of 94.71 per cent. There is thus seen to be
no practical advantage in combining arsenate of lead with nicotine
sulphate in sprays designed to control the codling moth (plats Nos.
1 and 38).

EXPERIMENTS PERFORMED AT GRAND JUNCTION, COLO.

Experiments similar to the preceding were also performed at
Grand Junction, Colo. Of the 12 plats sprayed, only 2 were sprayed
with nicotine sulphate, but since the results obtained using arsenate
of lead vary so greatly, the data from 4 of the latter plats are given
in Table VI, so that the results from the plat sprayed with nicotine
sulphate may be compared with those from the plats sprayed with
arsenate of lead alone and also with the results from the plat sprayed
with arsenate of lead and nicotine sulphate combined. In plats on
which it was applied (i. e., all except plats Nos. 10, 14, and 15),
the calyx application was made with a Bordeaux type of nozzle
which delivered a fairly coarse and driving spray; a mist type of
nozzle was used for all subsequent applications. With this exception
the same spraying equipment was used for all plats except the checks.

At various times throughout the growing season and at harvest
time the apples on eight trees in each plat (four in each of the two
check plats) were examined; the results of these examinations, to-
gether with the treatment of the several plats, are given in Table VI.

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 17

TABLE VI.—Codling-moth injury as shown by examination of both fallen and
picked fruit from experimental plats at Grand Junction, Colo., 1917.

Number of applications.| Tota] Ae |

number | Fallen Total
Plat No.| Formula of insecticide of apples | Sexre | apples
: : For For apples | free from | ,_ see free from
first | second | Total. | exam- Worms. | orms worms.
brood. | brood. ined. J

Per cent. | Per cent. | Per cent.
2 | 1 pound of powdered arse- |

nate of lead to 50 gallons |
OL Water eee ae eas 4 2 6 23, 508 37.75 | 72.16 | 62.09
Nicotine sulphate (1:800) - . 4 2 6

me OO

29, 881 Aisd2) | 58. 33 | 37. 96
1 pound of powdered arse- :
nate oflead to 50 gallons |
of water plus nicotine ey |
sulphate (1:800).-.....-.-. 4 2 6 24, 003 40. 97 | 84.17 67.50
8 | 1 pound of powdered arse- | |
nate oflead to 50 gallons

olswaten.fe-22 22-2 S362: 3 2 5 | 38,874 48. 28 | 82.31 73. 49

9 | Same as above. .........-.- 4 3 7 47,773 47.74 | 85. 53 76. 53

10 | Same as above... -......-.- 13 2 5 37,628 22.83 | 60. 69 46.33
tévand15; | >Checic (amsprayed ot ess: ace lecee eo tee a 33, 882 736 | = 15,01 8.72

1 All three were cover applications, the calyx application being omitted.

Although the results in the preceding table vary considerably, it is
seen nevertheless that nicotine sulphate when used alone was ineffi-
cient (plat No. 3).

EXPERIMENTS PERFORMED AT ROSWELL, N. MEX.

The experimental work conducted at Roswell consisted in a com-
parison of the efficiency of nicotine sulphate with that of arsenate of
lead alone and also with that of arsenate of lead combined with nico-
tine sulphate. For this purpose four plats, lying in a 640-acre tract
of apple trees, were selected ; they were similar in all respects and the
trees, about 20 years old, were of the Ben Davis variety. Following
the regular 5-spray schedule, all the plats, except the check (No.
4), were sprayed on the following dates: April 25, May 15, June 14,
July 18, and August 14. During the first application about 21
gallons of spray material were applied to each tree, but during each
subsequent application only about 17 gallons per tree were used.
Bordeaux nozzles were used for the calyx application and a mist
type for the other applications. A power sprayer, holding 200
gallons, was employed, and the pressure was maintained at 200
pounds with three leads of hose.

During these experiments the dates and amounts of rainfall are
as follows: May 6, 0.23 inch; July 19, 0.03 inch; July 20, 0.03 inch;
August 1, 0.54 inch; August 2, 0.47 inch; August 15, 0.15 inch;
August 17, 0.60 inch; and August 18, 0.93 inch, giving a total of
2.98 inches.

The details pertaining to the plats, formulas of application, and
results of the foregoing experiments are given in Table VII.

18 BULLETIN 938, U. S. DEPARTMENT OF AGRICULTURE.

TaBLeE VII.—Codling-moth injury as shown by examination of both fallen and
picked fruit from experimental plats at Roswell, N. Mezx., 1917.

Fruit record.

Plat Number of applications and formula of each. Total Fallen Har- Total
No. number anes vested pales
of apples PP apples PP
free from free from
exam- | Yo free from | _~
ined. ESD conse | CEES
1 | 5 applications of 1 pound of powdered arsenate of lead Per cent. | Per cent. | Per cent.
BOLO callonSofwatereseesecest bes see eeee eee reese 1 33,472 93. 64 97.66 96. 88
2 | 5 applications of 1 pound of powdered arsenate of lead
to 50 gallons of water-+nicotine sulphate (1:800)+ 3
Pound oflaundrysoapeeeeeeee eset ee ee eae e eee eee 27,011 85.55 98.99 97.00
3 | 5 applications of nicotine sulphate (1:800)+ 3 pound of
laundry soap to 50 gallons of water................-.. 3 6,170 88. 01 93. 43 91.94
AU MUnsprayed.. ihe eee eine bcs e ape alsa tte Chars weiss Momieis 414,401 52.06 50. 01 51.53
1 On 6 trees. 2 On 4 trees. 3 On 4 trees. 4 On 12 trees.

From Table VII it is seen that the trees sprayed with nicotine
sulphate (plat No. 3) yielded a crop of apples 92 per cent sound,
while those sprayed with arsenate of lead (plats Nos. 1 and 2) yielded
a crop 97 per cent sound, and that the addition of nicotine sulphate to
the arsenate of lead mixture (plat No. 2) did not materially increase
the percentage of sound fruit.

CONCLUSIONS FROM FIELD EXPERIMENTS.

According to the work conducted during the season of 1917, it is
shown that nicotine sulphate 1:800 with soap gave a fair degree of
control for the codling moth at Benton Harbor, Mich., and at Ros-
well, N. Mex., but that it was not as effective as 1 pound of powdered
arsenate of lead to 50 gallons of water; and also that there was no
practical advantage in combining arsenate of lead and nicotine sul-
phate in sprays designed to control the codling moth. Of course it
is well known that nicotine sulphate controls aphids on fruit trees,
but this phase of the subject is not considered in this paper. At
Grand Junction, Colo., where the infestation was much heavier, nico-
tine sulphate 1: 800 without soap was inefficient against the codling
moth.

(4)

(5)

(9)

NICOTINE SULPHATE AS AN OVICIDE AND LARVICIDE. 19

LITERATURE CITED.

[Dr SELLEM, F. E.]
1916. Nicotine sulfate for codlin moth control. Jn Ann. Rept. Hort.
Dept., Yakima Co., Wash., p. 62-72.
EATON, J. S., and WATERBURY, H. E.
1917. Codlin moth experimental work in Ross orchard. Jn Ann, Rept.
District Hort. Inspector, Yakima Co., Wash., p. 27-42.

FEYTAUD, J.
1912. Action des insecticides sur les ceufs de la cochylis et de l’eudémis.
In Bul. Soc. d’Etude et de Vulgarisation de la Zool. Agr., Bor-
deaux, p. 1-20.
Lovett, A. L.
1917. Nicotine sulphate as a poison for insects. Jn Jour. Econ. Ent., v.
10, no. 3, p. 333-337.

1918. Nicotine sulphate an effective ovicide for codling moth eggs. Notes
in Jour. Eeon. Ent., v. 11, no. 1, Feb., p. 149-150.
McInpboo, N. E.
1916. Effects of nicotine as an insecticide. In Jour. Agr. Research, v. 7,
NO: 3. p. 89-122, 3 pl
Moore, WILLIAM, and GRAHAM, S8. A.
1917. A neglected factor in the use of nicotine Sulphate as a spray. Jn
Jour. Agr. Research, v. 10, no. 1, p. 47-50.
PACKARD, A. S.
1903. A text-book of entomology. New York.
SAFRO, V. I.
1917. How to test for the presence of nicotine on sprayed plants. Jn
Jour. Econ. Ent., v. 10, no. 5, Oct., p. 459-461.

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