Spring populations of the green peach aphid on peach trees and the role of natural enemies in their control


Tamaki, G.

Environmental Entomology 2(2): 186-191

1973


A 2-year study of the spring population of Myzus persicae (Sulzer) on peach trees showed that the number of surviving fundatrices reaching reproductive maturity represented less than 2% of the overwintering eggs. Colonies established from surviving fundatrices protected from natural enemies by sleeve cages displayed a tremendous numerical recovery. For example, in a protected environment (cage) the average number of alate aphids per stem mother was 3596 in 1970, and 1080 in 1971. In contrast, on unprotected twigs the natural enemies, primarily coccinellid and syrphid predators, played a major role in reducing the production of alate aphids by an estimated 95% in both years (based on counts of immature aphids).

Spring
Populations
of
the
Green
Peach
Aphid'
on
Peach
Trees
and
the
Role
of
Natural
Enemies
in
Their
Control"
GEORGE
TAMAKI
Yakima
Agricultural
Research
Laboratory,
Agric.
Res.
Serv.,
USDA,
Yakima,
Washington
98902
ABSTRACT
A
2
-year
study
of
the
spring
population
of
Myzus
persicae
(Sulzer)
on
peach
trees
showed
that
the
number
of
surviving
fundatrices
reaching
reproductive
maturity
repre-
sented
less
than
2%
of
the
overwintering
eggs.
Colonies
established
from
surviving
fundatrices
protected
from
natural
enemies
by
sleeve
cages
displayed
a
tremendous
numerical
recovery.
For
example,
in
a
protected
environment
(cage)
the
average
number
of
alate
aphids
per
stem
mother
was
3596
in
1970,
and
1080
in
1971.
In
con-
trast,
on
unprotected
twigs
the
natural
enemies,
primarily
coccinellid
and
syrphid
predators,
played
a
major
role
in
reducing
the
production
of
alate
aphids
by
an
esti-
mated
95%
in
both
years
(based
on
counts
of
immature
aphids).
In
our
continuing
effort
to
develop
an
integrated
control
program
for
suppression
of
the
green
peach
aphid,
Myzus
persicae
(Sulzer),
on
peach
trees,
we
have
previously
studied
the
ecology
and
the
biology
of
this
species
in
autumn
(Tamaki
and
Weeks
1968).
The
present
paper
reports
the
1st
study
of
the
green
peach
aphid
on
peach
trees
in
the
spring.
We
wished
to
determine
the
survival
of
eggs
and
funda-
trices,
the
potential
for
population
growth,
the
nor-
mal
production
of
alate
aphids,
and
the
impact
of
natural
enemies
on
the
spring
population.
Therefore,
during
the
spring
of
1970
and
1971,
the
overwinter-
ing
eggs,
fundatrices,
and
virginoparae
were
studied
at
the
USDA
peach
orchard
at
Yakima,
Wash.
Materials
and
Methods
Two
separate
tests
were
conducted
each
year.
From
late
February
to
early
May,
the
survival
of
overwintering
eggs
and
fundatrices
was
observed
and
recorded;
from
April
to
June,
we
studied
the
popu-
lation
growth
of
green
peach
aphids
exposed
to
or
protected
from
its
natural
enemies.
Thus,
for
the
1st
test
in
1970,
51
twigs
of
previ-
ous
year's
growth
which
contained
2
or
more
dis-
tended
eggs
were
selected
on
Feb.
24.
All
twigs
were
rated
(from
highest
to
lowest)
by
the
number
of
eggs
per
twig.
Then
this
rating
was
used
to
select
twigs
for
each
of
the
3
treatments
so
each
treatment
was
applied
to
17
twigs
that
had
almost
an
equal
number
of
total
eggs.
The
1st
treatment
consisted
of
placing
17
twigs
in
individual
sleeve
cages
that
covered
ca.
10-12
in.
of
the
terminal
tips
so
the
eggs
and
hatching
fundatrices
were
protected
from
predators
and
parasites
and
other
aphids
were
ex-
cluded.
The
cage
was
made
of
nylon
organdy
fi
tted
tightly
over
a
cylindrical
4-in.-diam
wire
frame.
It
was
fastened
to
the
twigs
by
tying
the
overlapping
ends
of
the
cloth
covering
to
the
twig
with
soft
wire.
Then
the
caged
twigs
were
supported
on
the
trees
by
securing
wire
guides
from
the
terminal
end
of
the
Hemiptera:
Aphididae.
2
In
cooperation
with
the
College
of
Agriculture,
Research
Center,
Washington
State
University,
Pullman
99163.
Received
for
publication
8
Sept.
1972.
3
Mention
of
a
proprietary
product
does
not
constitute
en-
dorsement
by
the
USDA.
caged
twigs
to
other
stronger
twigs.
The
2nd
treat-
ment
consisted
of
banding
the
basal
end
of
the
selected
twigs
with
masking
tape
10-12
in.
from
the
tip
and
putting
a
ring
of
Stikemo
on
the
band
so
the
apterous
aphids
could
not
leave
these
semi
-
isolated
twigs
but
the
aphid
colonies
on
the
twigs
were
exposed
to
fl
ying
predators
or
parasites.
The
3rd
treatment
was
the
control:
these
17
twigs
were
simply
tagged
and
numbered
10-12
in.
behind
the
tips.
A
hand
lens
was
used
to
determine
the
number
of
distended
and
shriveled
eggs
on each
twig.
The
2nd
test
in
1970
was
made
with
30
twigs
on
Apr.
22.
Each
had
either
a
stem
mother
or an
in-
cipient
colony,
and
all
were
rated
as
in
the
1st
test
except
that
the
rating
was
based
on
the
number
of
aphids
instead
of
the
number
of
eggs.
The
treat-
ments
used
were
the
same
as
in
the
1st
test,
but
only
10
twigs
each
were
tested.
However,
the
twig
cages
were
made
of
6-in.-diam
cylindrical
wire
frames
to
allow
for
leaf
growth.
The
same
2
tests
were
repeated
in
1971
except
that
10
twigs
were
exposed
to
each
treatment.
Also,
in
the
1st
test
in
1971,
only
the
uncaged
twigs
were
tested.
In
all
tests,
the
eggs
on
all
twigs
were
counted
1-3
times
a
week.
However,
during
the
period
of
alate
production,
counts
were
made
at
least
2
times
a
week,
and
after
each
count,
alate
adults
were
re-
moved
from
the
caged
twigs
to
prevent
larviposition
on
peach
leaves.
However,
Davis
and
Landis
(1951)
reported
that
only
3
nymphs
were
produced
from
152
alates
caged
on
peach
trees
and
that
none
of
these
nymphs
reached
maturity.
To
determine
the
differences
in
the
air
tempera-
ture
around
the
caged
and
uncaged
twigs,
we
used
a
battery
-operated
thermister-thermometer
fi
tted
with
small
flexible
nylon
probes.
Results
and
Discussion
Survival
of
Eggs
and
Fundatrices
In
late
February
1970,
86-92%
of
the
eggs
in-
spected
were
distended,
and
each
twig
had
an
aver-
age
of
0.27
fundatrix
nymphs
(Table
1).
However,
all
these
nymphs
were
in
the
1st
stadium,
which
in
-
186
April
1973
TAMAKI:
NATURAL
ENEMIES
OF
GREEN
PEACH
APHID
Table
1.
—Survival
of
distended
eggs
and
live
fundatrices
of
the
green
peach
aphid.
1970
and
1971.•
187
Date
Banded
twigs
(total
86
eggs)
Caged
twigs
(total
91
eggs)
Control
twigs
(total
86
eggs)
%
distended
No.
live
eggs
fundatrices
%
distended
eggs
No.
live
fundatrices
%
distended
eggs
1970
No.
live
fundatrices
Feb.
24
86
2.4
86
3.5
92
2.4
Mar.
9
83
3.5
77
7.6
74
5.9
Mar.
17
74
1.8
60
2.9
63
2.4
Mar.
24
44
2.4
40
2.9
59
2.4
Apr.
3
22
2.4
6
2.9
11
1.8
Apr.
15
1
2.4
0
2.9
0
1.8
Apr.
21
0
2.4
0
2.9
0
1.2
1971
(total
236
eggs)
Feb.
28
50
13
Mar.
10
43
11
Mar.
19
35
2
Mar.
24
34
1
A
pr.
2
29
0
Apr.
14
14
0
Apr.
23
8
0
May
3 3
0
May
12
1
0
1970
data
adjusted
for
an
average.
10
twigs.
dicated
that
they
had
recently
hatched.
The
time
of
1st
egg
hatch
is
not
known,
but
in
past
years
we
have
found
a
few
nymphs
on
peach
trees
by
mid
-
February.
Doncaster
and
Gregory
(1948)
men-
tioned
that
the
date
of
hatching
seemed
to
be
influ-
enced
by
the
severity
of
the
preceding
winter.
The
peak
number
of
nymphs
occurred
Mar.
9,
an
average
0.35-0.76
aphids/twig
in
all
treatments.
Then
as
the
bud
swell
stage
began
Mar.
17,
the
number
of
nymphs
found
on
each
twig
began
to
decrease
in
all
treatments,
and
the
number
of
dis-
tended
eggs
continued
to
decrease.
By
the
time
the
buds
started
to
show color
Apr.
3,
only
0.18-0.29
nymphs/twig
were
found
and
only
6-22%
distended
eggs.
Of
the
original
444
overwintering
eggs
found
on
the
51
twigs
used
in
Test
1,
1970,
only
9
stem
mothers
reached
maturity
and
established
colonies,
5
in
caged
twig
and
2
each
in
the
other
2
treatments.
Since
the
number
of
established
colonies
was
thus
quite
small,
we
repeated
the
same
test
in
1971
with
uncaged,
unbanded
twigs.
In
the
1971
test,
the
uncaged
twigs
selected
had
ea.
3
times
as
many
eggs
per
twig
as
those
used
in
1970.
However,
as
Table
1
shows,
only
50%
of
the
eggs
checked
on
Feb.
28
were
distended,
and
each
twig
had
an
average
of
only
1.3
newly
hatched
nymphs.
At
bud
swell
on
May
24,
only
1
nymph
was
found
on
10
twigs;
and
thereafter
no
nymphs
were
found on
any
of
the
experimental
twigs.
How-
ever,
colonies
were
found
on
twigs
in
each
peach
tree
so
we
could
study
the
population
growth
of
established
colonies.
Thus,
over
a
2
-year
period,
less
than
2%
of
the
overwintering
aphid
eggs
survived
to
produce
mature
stem
mothers.
Even
when
a
large
number
of
dis-
tended
eggs
are
available
in
spring,
few
nymphs
re-
sult,
either
because
the
eggs
are
not
all
viable
or
because
the
nymphs
are
killed
immediately
upon
hatching.
Limitations
of
Sleeve
Cages
Although
sleeve
cages
were
not
important
in
the
experiment
dealing
with
survival
of
eggs
and
funda-
trices,
they
did
play
a
key
role
in
the
experiment
dealing
with
population
growth,
predator
impact,
and
alate
production.
We
therefore
considered
their
limitations
in
our
interpretation
of
the
data
obtained
through
their
use.
Smith
and
DeBach
(1942)
reported
using
sleeve
cages
to
exclude
natural
enemies
of
scale
insects,
but
they
mentioned
several
limitations
of
the
cages,
one
being
that
they
prevented
natural
dispersal
of
the
caged
insect.
In
our
study,
it
was
sometimes
apparent
that
dispersal
was
being
prevented,
for
example
when
populations
of
aphids
reached
a
peak
by
the
3rd
generation
and
the
virginoparae
aphids
fully
covered
the
available
leaf
area.
However,
by
this
time,
most
of
the
aphids
were
destined
to
be
winged
aphids,
and
the
winged
aphids
were
periodi-
cally
removed
from
the
cages.
Also,
in
the
banded
treatment,
only
a
few
aphids
were
ever
caught
in
the
sticky
bands.
Thus
these
aphids
never
increased
to
the
numbers
found
inside
the
sleeve
cages.
(From
our
observations
of
aphid
colonies
on
peach
trees,
the
green
peach
aphid
at
this
time
of
year
stays
in
compact
colonies,
indication
of
rather
sedentary
be-
havior.)
188
ENVIRONMENTAL
ENTOMOLOGY
Vol.
2,
no.
3000
1000
X
500
O.
17
111
100
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50
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22
28
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4
APR
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cCAGED
TWIG
12
15 18
MAY
22
28
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15
JUN
2
0
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0
100
50
1-
AVG.
NO.
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TWIG
(LINE
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1000
500
100
•••-•-•
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BANDED
50
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GeTV/IG
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--GAGED
TWIG
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-
1130
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en
41
50
1-
a
21
26
APR
7
10
14
17
20
24
28
MAY
4
7
10
JUN
FIG.
1.
—Population
curves
for
green
peach
aphids
on
peach
twigs
held
at
3
different
conditions
and
production
of
alates
on
caged
twigs
in
1970
(left).
Ftc.
2.
—Population
curves
for
green
peach
aphids
on
peach
twigs
held
at
3
different
conditions
and
production
of
alates
on
caged
twigs
in
1971
(right).
Smith
and
DeBach
(1942)
also
mentioned
that
physical
factors
such
as
temperature,
wind,
and
light
were
modified
by
the
sleeve
cages.
Of
these
factors,
the
cage
and
the
ambient
air
temperatures
would
probably
have
the
greatest
effect
on
the
popu-
lation
growth
since
temperature
affects
the
develop-
mental
rates
of
the
aphids.
In
our
tests,
cage
tem-
peratures
averaged
1-2.4°C
higher
than
the
tem-
perature
of
the
ambient
air,
and
during
the
part
of
the
day
when
temperatures
were
highest,
they
aver-
aged
2-4°C
higher
(during
the
early
sunlight
hours
they
were
only
ca.
0.5-1°C
higher).
However,
in
the
spring,
temperatures
high
enough
to
be
detrimental
to
aphid
development
are
probably
rare;
therefore,
the
higher
temperatures
inside
the
cages
probably
increased
the
developmental
rates.
Population
Growth
In
the
2nd
experiment
each
year,
twigs
with
either
a
stem
mother
or
an
incipient
colony
were
selected
so
we
could
determine
the
growth
potential
of
the
spring
population
of
the
green
peach
aphid
on
peach
trees.
On
Apr.
22,
1970,
when
we
covered
the
twigs
with
sleeve
cages,
the
aphids
on
each
twig
averaged
1
stem
mother
and
11.9
progeny.
The
population
increased
at
an
exponential
rate
and
peaked
May
25
when
an
average
of
3217
aphids
was
present
in
each
cage
(676
winged
adults
had
been
removed
for
a
3
-day
interval).
After
May
25,
the
population
of
aphids
in
the
cages
declined
rapidly
(Fig.
1).
In
1970,
in
the
other
2
treatments
(banded
and
control
twigs),
the
aphids
were
exposed
to
natural
enemies.
Thus
on
Apr.
28,
6
days
after
the
initial
count,
the
twigs
in
both
these
treatments
had
more
aphids
per
twig
than
twigs
in
the
cage
treatment.
Also
on
May
4,
these
populations
were
continuing
to
in-
crease
though
at
a
much
slower
rate
than
in
the
cages
(Fig.
1).
However,
none
of
the
uncaged
colon-
ies
of
aphids
rose
above
an
average
of
100
apterous
aphids/twig,
and
both
populations
usually
fluctuated
between
35
and
100
aphids/twig.
(In
this
paper,
I
have
defined
apterous
aphids
to
include
immature
aphids
with
wing
pads.)
Then
from
about
mid
-May,
the
size
of
the
2
types
of
colonies
declined
steadily
because
of
emigration
or
the
removal
of
the
winged
aphids.
In
1971,
the
populations
of
aphids
in
the
sleeve
cages
increased
at
an
exponential
rate
until
May
12,
peaked
May
20
(an
average
843
aphids/cage;
148
winged
adults
were
removed
for
a
3
-day
interval),
and
then
declined
rapidly
(Fig.
2).
In
contrast,
the
uncaged
colonies
of
aphids
never
exceeded
an
aver-
age
50
aphids/twig.
Thus,
ca.
4
times
as
many
aphids
were
found
in
sleeve
cages
in
1970
as
in
1971.
Since
the
temper-
ature
records
in
April
and
May
in
both
years
were
not
sufficiently
different
to
be
the
primary
explana-
tion,
we
will
need
more
environmental
data,
such
as
peach
tree
conditions
and
physical
conditions
during
the
winter
and
spring,
to
isolate
the
factors
that
are
involved
in
such
large
differences
in
population.
April
1973
000
-
0
Lu
1000-
u
N
LU
4
0
z
CUMULATIVE
AVG
1007
0
TAMAKI:
NATURAL
ENEMIES
OF
GREEN
PEACH
APHID
189
/
,0-0-0-0-0
j197
0
0
/
--'.--•-•-•
19
71
I/
0
APR
5
10
15
20
25
5
10
IS
20
MAY
JUNE
FIG.
3.
—Comparison
of
the
cumulative
number
of
alates
produced
on
caged
twigs
in
1970
and
1971.
Impact
of
Natural
Enemies
As
previously
mentioned,
fewer
aphids
were
pres-
ent
on
uncaged
twigs
than
on
caged
twigs
during
the
spring
of
each
year.
This
difference
is
attributed
to
the
activity
of
natural
enemies.
Thus,
on
May
4,
1970
(Table
2),
the
percentage
of
apterous
aphids
on
the
uncaged
twigs
was
only
42%
that
on
the
caged
twigs
even
though
the
popu-
lation
on
the
uncaged
twigs
had
increased
from
the
previous
counts;
a
similar
situation
occurred
in
1971
(Table
2).
Also,
on
May
4,
we
found
evidence
of
activity
by
natural
enemies
on
8
of
the
10
control
twigs
(from
the
presence
of
natural
enemies,
mum-
mies,
fed
-on
aphids,
predator
excreta,
etc.).
Table
2
shows
the
census
of
syrphids
and
coccinellids;
how-
ever,
these
counts
represent
only
the
population
of
natural
enemies
present
at
the
time
of
the
count,
a
period
of
5-1.5
min.
Thus,
they
are
only
a
small
fraction
of
the
actual
predator
activity
taking
place
on
the
twigs
throughout
the
day.
For
instance,
coc-
cinellid
adults
were
highly
active
and
were
observed
flying
to
twigs
where
they
searched
and
fed
for
a
few
minutes
and
then
flew
to
other
twigs.
At
times,
ca.
20
coccinellid
adults
were
counted
searching
on
I
medium
-size
peach
tree.
By
May
18,
1970,
the
number
of
apterae
on
uncaged
twigs
was
only
2%
the
population
on
the
caged
twigs
(Table
2),
and
it
remained
at
this
level
for
the
next
20
days.
Then
from
June
1
to
12,
the
population
in
the
cages
de-
clined
faster
than
the
population
on
the
uncaged
twigs.
In
1971,
both
coccinellids
and
syrphids
were
less
abundant;
indeed,
syrphid
predation
was
negligible,
probably
because
the
population
of
aphids
was
lower
in
1971
than
in
1970.
As
reported
for
autumn
(Tamaki
et
al.
1967),
syrphid
oviposition
increased
as
the
number
of
aphids
per
leaf
increased
until
it
reached
a
high
of
30-40
aphids/leaf.
However,
the
coccinellids,
though
they
were
fewer
in
1971,
still
played
the
primary
role
in
suppressing
the
popu-
lation
of
aphids.
Indeed,
even
when
both
syrphids
and
coccinellids
were
present,
the
coccinellids
prob-
ably
had
a
greater
impact
on
the
aphid
population
in
the
spring
than
the
syrphids
because
of
their
more
voracious
feeding
habits,
powers
of
dispersal,
and
the
fact
that
both
larvae
and
adults
feed
on
aphids.
The
2
principal
species
of
coccinellids
present
dur-
ing
the
studies
were
Coccinella
transversoguttata
richardsoni
Brown,
the
most
abundant
species,
and
Hippodamia
convergens
Guerin-Meneville.
Parasites
and
hyperparasites
of
the
green
peach
aphid
were
frequently
observed
on
the
twigs,
but
only
a
few
mummified
aphids
were
found.
Most
of
these
aphids
were
parasitized
by
Praon
sp.,
probably
the
same
species
found
in
the
autumn
(Tamaki
and
Halfhill
1968),
which
is
probably
a
new
species
near
the
European
Praon
abjectus
(Haliday)
(Tamaki
and
Halfhill
1968).
Only
a
few
Orius
tristicolor
(White)
and
chrysopid
eggs
were
ever
found
on
the
twigs. In
1970,
no
diseased
aphids
were
observed,
but
in
1971,
we
found
5
dead
aphids
infected
with
a
fungus:
therefore,
disease
played
only
a
minor
role
in
sup-
pressing
the
population
of
aphids
in
both
years.
In
our
study,
unlike
many
others
made
of
aphido-
phagous
predators
(Atwal
and
Sethi
1963),
the
feed-
ing
of
the
voracious
predators
was
synchronized
with
the
buildup
of
aphid
populations
on
peach
trees.
Thus
the
predators
were
able
to
suppress
the
popu-
lation
early
in
the
growth
phase
before
it
began
to
display
an
exponential
rate
of
growth
(Fig.
1
and
2),
and
the
98%
reduction
of
the
populations
on
the
uncaged
twigs
was
primarily
the
result
of
this
high
level
of
activity
by
the
complex
of
natural
enemies
found
in
the
orchard.
Alate
Production
Our
ultimate
goal
in
controlling
the
green
peach
aphid
on
peach
trees
is
to
suppress
the
production
of
alate
aphids,
thereby
reducing
the
number
of
potential
vectors
of
virus
diseases
in
vegetable
and
sugarbeet
crops
in
early
summer.
We
therefore
at-
tempted
to
determine
the
potential
average
produc-
tion
of
alates
from
aphid
colonies
in
spring.
In
1970,
the
earliest
winged
aphids
were
found
May
4
(5
on
caged
twigs,
1
on
uncaged
twigs):
in
1971,
the
earliest
alates
were
found
May
7
(3
on
caged
twigs,
3
on
uncaged
twigs).
The
higher
tern-
perature
in
the
cages
therefore
caused
no
apparent
difference
in
time
of
the
earliest
appearance
of
alates.
In
1970,
the
last
alate
aphids
were
found
in
cages
190
ENVIRONMENTAL
ENTOMOLOGY
Vol.
2,
no.
2
Table
2.
—The
impact
of
natural
enemies
on
the
populations
of
the
green
peach
aphid
on
uncaged
twigs.
1970
and
1971.'
Aphids
on
uncaged
twigs
No.
twigs
with
evidence
of
activity
of
No.
of
natural
enemies
Para-
sitized
As
%
of
no.
of
aphids
on
caged
Syrphids
Coccinellids
Larvae
Eggs
Date
No.
twigs
natural
enemy
Adult
Larvae
Eggs
aphids
1970
Apr.
22
146
1
13
0
1
28
489
162
1
1
5
May
4
919
42
8
1
6
4
70
12
884
12
7
1
4
5
15
824
8
6
6 6
8
2
18
361
2
5
2
3
4
33
20
380
2
3
2
22
571
2
3
1
2
1
2
25
497
2
5
1
1
5
28
512
3
6
4
3
June
1
657
8
5
2
I
1
3
552
18
7
2
3
8
337
80
6
3
3
II
220
198
4
1
12
159
430
2
0
27
10
0
0
1971
Apr.
21
66
550
0
26
148
239
2
1
May
3
314
53
6
2 2
5
226
12
6
10
295
7
8
1
12
155
2
7
1
2
17
343
5
1
24
207
4
6
3
2
26
1
18
4
5
1
2
28
46
2
6
5
June
1
10
1
6
1
2
3
4
1
<
0
7
6
3
0
10
0
0
Avg
for
10
twigs.
June
27;
however,
in
1971,
the
test
was
terminated
June
11
when
only
a
few
apterous
aphids
that
were
destined
to
be
alates
were
still
present
on
caged
twigs.
The
peak
production
of
alates
(Fig.
1
and
2)
on
caged
twigs
occurred
between
May
25
and
June
1,
1970
(from
225
to
244
removed/day
per
cage)
and
between
May
21
and
24,
1971
(average
of
88
alates
removed/day
per
cage).
The
potential
of
spring
colonies
of
green
peach
aphids
to
produce
and
create
large
numbers
of
alates
in
a
relatively
short
time
in
cages
is
shown
graphi-
cally
in
Fig.
3
for
the
2
years.
As
indicated,
in
1970,
an
average
yield
of
3596
alate
aphids/caged
twig
was
obtained
from
single
spring
colonies:
in
1971,
the
average
was
1080
alates/caged
twig.
How-
ever,
the
exact
number
of
alate
adults
produced
on
uncaged
twigs
could
not
be
determined
because
of
the
emigration
of
alate
aphids.
We
therefore
com-
pared
the
number
of
apterae
on
the
caged
twigs
with
the
number on
the
uncaged
twigs
during
the
period
of
alate
production
(May
4
to
June
22,
1970,
and
May
7
to
June
10,
1971).
The
data
showed
that
the
apterous
population
on
uncaged
twigs
was
only
4.8
and
4.3%
that
on
the
caged
twigs.
Thus,
the
esti-
mated
production
of
alates
on
unprotected
twigs
(ex-
posed
to
the
natural
enemies
of
the
green
peach
aphid)
was
reduced
nearly
95%
below
its
potential.
REFERENCES
CITED
Atwal,
A.
S.,
and
S.
L.
Sethi.
1963.
Predation
by
Coccinella
septempunctata
L.
on
the
cabbage
aphid,
Lipaphis
erysimi
(Kalt.)
in
India.
J.
Anim.
Ecol.
32:
481-8.
Davis,
E.
W.,
and
B.
J.
Landis.
1951.
Life
history
of
the
green
peach
aphid
on
peach
and
its
relation
to
the
aphid
problem
on
potatoes
in
Washington.
J.
Econ.
Entomol:
44:
586-90.
Doncaster,
J.
P.,
and
P.
H.
Gregory.
1948.
The
spread
of
virus
diseases
in
the
potato
crop.
Res.
Comm.
Rep.
Ser.
&
His
Majesty's
Stationery
Of-
fi
ce,
London,
189
p.
Smith,
H.
S.,
and
P.
DeBach.
1942.
The
measure-
ment
of
the
effect
of
entomophagous
insects
on
pop-
ulation
densities
of
their
host.
J.
Econ.
Entomol.
35:
845-9.
Tamaki,
G.,
11.
J.
Landis,
and
IL
E.
Weeks.
1967.
Autumn
populations
of
green
peach
aphid
on
peach
trees
and
the
role
of
syrphid
flies
in
their
control.
Ibid.
60:
433-6.
Tamaki,
G.,
and
J.
E.
Halfhill.
1968.
Bands
on
April
1973
TAMAKI:
NATURAL
ENEMIES
OF
GREEN
PEACH
APHID
191
peach
trees
as
shelters
for
predators
of
the
green
peach
aphid.
Ibid.
61:
707-11.
Tamaki,
C.,
and
R.
E.
Weeks.
1968.
Use
of
chem-
ical
defoliants
on
peach
trees
in
integrated
program
to
suppress
populations
of
green
peach
aphids.
Ibid.
61:
431-5.
The
Morphogenetic
Effects
of
Two
Juvenile
Hormone
Analogues
on
Larvae
of
Imported
Fire
Ants'
'
E.
W.
CUPP'
AND
J.
O'NEAL'
Department
of
Biology,
University
of
Southern
Mississippi,
Hattiesburg,
Miss.
39401
ABSTRACT
This
is
the
1st
report
of
the
morphogenetic
effects
of
2
juvenile
hormone
analogues
on
larvae
of
Solenopsis
richteri
Forel
and
S.
invicta
Buren.
Both
analogues
were
capable
of
preventing
pupation
but
isopropyl
11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate
proved
consistently
effective
when
administered
topically,
orally,
or
by
trophallaxis.
Anomalous
prepupae,
pupae,
and
workers
occurred
when
developing
larvae
came
in
contact
with
concentrations
of
5
parts
per
million
or
more.
Ethyl
3,7,11-trimethyldodeca-
2,4-dienoate
proved
less
effective
when
administered
by
trophallaxis.
The
use
of
juvenile
hormone
(JH)
and
its
ana-
logues
as
a
new
approach
to
insect
control
has
emerged
as
a
result
of
basic
physiological
and
bio-
chemical
studies
of
insect
development.
This
hor-
mone
maintains
juvenility
in
the
growing
phase
of
development
and
its
subsequent
drastic
drop
in
titer
to
a
fi
nal
undetectable
amount
is
the
key
for
matura-
tion
to
the
imago.
JH
later
reappears
in
female
adults
as
a
gonadotropic
hormone
and
may
also
be
involved
in
the
activity
of
male
accessory
glands.
The
appearance
of
juvenile
hormone
or
active
analogues
at
an
unnatural
time
in
metamorphosis
could
then
be
catastrophic
to
developing
insects.
Ex-
tended
presence
of
JH
or
JH
analogues
could
cause:
(
1)
failure
to
pupate;
(2)
failure
to
mature
to
the
adult
stage
from
the
last
nymphal
instar;
(3)
de-
velopment
of
abnormal
pupae;
and
(4)
death.
Therefore,
the
potential
use
of
these
compounds
as
3rd
-generation
insecticides
is
quite
high
(Williams
1967).
The
possibility
of
resistance
development
is
unlikely
since
JH
is
an
insect
invention
and
the
high
degree
of
specificity
insures
a
narrow
spectrum
of
activity.
Additionally,
JH
and
JH
analogues
are
highly
biodegradable
and
therefore
would
not
be-
come
concentrated
in
food
chains.
Roller
et
al.
(1967)
have
shown
a
juvenile
hor-
mone
of
Hyalophora
cecropia
(L.)
to
be
the
methyl
ester
of
the
epoxide
of
a
fatty
acid
derivative.
JH
is
related
to
farnesol,
a
terpene
alcohol
(Gilmour
1965).
The
methyl
and
ethyl
ethers
of
this
terpenoid
mimic
many
of
the
effects
of
juvenile
hormone
(Wig-
glesworth
1963).
Certain
straight
-chain
terpenic
analogues
also
exhibit
JH
activity
(Zaoral
and
Slama
1970).
Good
activity
of
JH
analogues
has
been
observed
in
compounds
having
an
acyclic
terpenoid
skeleton
(Bowers
and
Thompson
1963,
Schwarz
et
al.
Hymenoptera:
Formicidae.
Received
for
publication
13
June
1972.
3
We
gratefully
acknowledge
the
assistance
of
the
Zoecon
Cor-
poration
for
providing
both
JH
analogues
and
the
Mississippi
De-
partment
of
Agriculture
and
Commerce
fur
providing
funds.
USDA
Fire
Ant
Research
Laboratory,
Gulfport,
Miss.
1970),
as
well
as
epoxidized
and
unepoxidized
aro-
matic
ethers
of
geraniol
(Bowers
1969,
Pallos
et
al.
1971).
With
these
available
data,
2
new
juvenile
hormone
analogues
were
examined
for
possible
morphogenetic
activity
against
developing
immatures
of
the
Solenop-
sis
sac
vissima
complex.
Both
Solenopsis
richteri
Forel
and
Solenopsis
invicta
Buren
(Buren
1972)
of
this
taxonomic
group
were
used
in
this
investiga-
tion.
The
analogues
were:
I.
ZR-512—Ethyl
3,7,11-tri
methyldodeca-2,4-dieno-
ate.
Empirical
formula:
C
17
1-1
3
„0
2
.
Molecular
weight:
266.
Physical
state:
colorless
liquid.
Specific
gravity:
0.8643.
Solubility:
soluble
in
nonaqueous
organic
solvents.
Water
solubility:
0.54
ppm.
IL
ZR-515—Isopropyl
11-methoxy-3,7,11-tri
methyl-
dodeca-2,4-dienoate.
Empirical
formula:
C
1
,1-1
34
0
3
.
Molecular
weight:
310.
Physical
state:
colorless
liquid.
Specific
gravity:
0.8856.
Solubility:
soluble
in
nonaqueous
organic
solvents.
Water
solubility:
1.39
ppm.
Materials
and
Methods
Colonies
of
imported
fi
re
ants
were
excavated
in
the
field
and
separated
and
maintained
in
the
labora-
tory
according
to
the
methods
described
by
Markin
(1968).
Aliquot
samples
of
brood
and
workers