Life-History of the Pecan Twig Girdler


Bilsing, S.W.

Journal of Economic Entomology 9(1): 110-115

1916


Oncidefes texana may cause serious damage to pecan 'trees, ' the cultivation of which has become an important industry in Texas, by the girdling of the branches for the purpose of egg-laying. ''This beetle has also been found on persimmon, elm, hickory, maple, pear, peach, etc. Oviposition begins after the twig has been girdled1; the central portion is generally left intact, but the weight of the branch is often sufficient to cause it to break off. Eggs are laid singly, or rarely in groups of three or four, at the base of the leaf buds, in an incision made in the bark. During the oviposition period, both male and female feed on the soft wood at the base of the leaf buds at the extremity of the branch. When nurseries are adjacent to forests, severe damage is often caused by migration of the adults from the surrounding trees. Females emerge from 25th August until the beginning of October. Oviposition begins from 12 to 29 days later, and may continue until December. About 175 eggs are deposited on an average by each female. The larva, which hatches in from 17 to 30 days, hollows out a cavity in the branch and feeds throughout the winter. The larval stage lasts from 288 to 328 days. Pupation occurs late in August or early in September, and the pupal stage, lasting for 12 or 14 days, is passed in the pupal burrow. The method of control by gathering fallen twigs and burning them in order to kill the larvae is practicable only where a pecan orchard is not situated near other trees. Experiments with lead arsenate proved effective in preventing migration to the pecan trees. In the discussion following, it was stated that the female usually oviposits in the main twigs, the girdles being cut at a distance of about 2 feet from the trunks of the smaller trees. In breeding experiments, moisture proved to be an important factor. A small number of larvae survived in branches which remained on the ground. Beetles were hot observed girdling branches which sloped downwards. A considerable percentage of adults were parasitized by a Tachinid fly.

110
JOURNAL
OF
ECONOMIC
ENTOMOLOGY
[VOI.
when
the
examination
was
made.
I
have
noticed
shallow
holes
that
were
made
in
the
apple
by
the
larvae,
but
in
most
cases
the
larvae
were
found
dead
in
the
holes,
showing
that
they
had
gotten
some
of
the
poison
in
eating
through
the
skin.
MR.
G.
D.
SHAFER:
Did
you
find
any
dead
larvae
in
these
side
injuries?
MR.
E.
P.
FELT:
No,
I
did
not
find
any.
I
did
not
look
closely
for
them.
PRESIDENT
GLENN
W.
HERRICK
:
Had
the
trees
been
sprayed?
MR.
E.
P.
FELT:
Yes,
they
had
been
sprayed.
Observations
on
habits
of
the
larva
hatching
after
late
deposition
of
eggs
was
included
in
the
experiment.
MR.
G.
D.
SHAFER:
Two
years
ago
in
Michigan
I
found
a
great
many
larvae
and
in
a
few
cases
I
was
able
to
find
dead
larvae
in
the
little
cups
of
the
injury.
I
wondered
if
the
larvae
had
gotten
some
poison
and
thus
succumbed
to
that.
MR.
E.
P.
FELT:
Lloyd
records
killing
larvae
in
that
way.
PRESIDENT
GLENN
W.
HERRICK
:
I
will
now
call
for
a
paper
by
Mr.
S.
W.
Bilsing.
LIFE-HISTORY
OF
THE
PECAN
TWIG
GIRDLER
By
S.
W.
BILSING,
College
Station,
Texas
INTRODUCTION
Pecan
growing
has
become
an
important
industry
in
Texas
and
the
means
of
controlling
the
insects
which
affect
both
the
tree
and
the
nut
are
of
great
importance.
In
the
autumn
of
1913
several
of
the
three-year-old
pecan
trees
in
the
orchard
of
the
Horticultural
Department
at
College
Station
were
severely
damaged
by
the
pecan
twig
girdler,
Oncideres
texana.
Upon
close
examination
it
was
found
that
the
damage
was
caused
by
a
single
female.
The
damage
was
so
great
that
it
was
decided
to
make
an
in-
vestigation
of
the
life-history
of
this
insect.
This
insect
was
marked
by
putting
a
drop
of
red
ink
on
the
right
wing
cover,
and
the
methods
of
oviposition
and
egg-laying
habits
were
closely
observed.
During
the
fall
of
1913
this
one
female
entirely
severed
one
young
tree
about
two
feet
from
the
ground
and
pruned
three
other
trees.
Every
limb
was
pruned
on
two
of
these
trees
and
a
third
was
pruned
almost
as
severely.
In
all,
16
limbs
were
severed
by
this
single
female.
In
each
case
the
limbs
severed
were
from
8
to
10
mm.
in
diameter.
Since
then
we
have
noted
individuals
which
cut
February,
'16]
BILSING:
PECAN
TWIG
GIRDLER
111
off
limbs
more
than
an
inch
in
diameter.
The
limbs,
however,
are
usually
7
to
10
mm.
in
diameter.
FOOD
PLANTS
This
insect
is
not
at
all
choice
in
the
selection
of
a
tree
upon
which
it
intends
to
girdle
limbs.
Pecan,
persimmon
and
the
various
species
of
elm
seem
to
be
preferred
to
the
others.
Pear
trees
are
also
often
severely
pruned.
From
the
observations
we
have
made
it
would
appear
that
most
any
kind
of
a
plant
may
be
selected
if
necessity
demands
it.
The
following
is
a
list
of
trees
on
which
the
insect
has
been
taken:
Pecan,
persimmon,
elm,
hackberry,
mesquite,
rose,
sweet
locust,
water
oak,
post
oak,
live
oak,
hickory,
maple,
pear,
and
peach.
EGG-LAYING
HABITS
The
limb
is
first
cut
off
although
this
habit
varies
to
some
extent
and
occasionally
some
of
the
eggs
are
deposited
before
the
limb
is
entirely
severed.
In
nearly
all
cases
the
adult
stands
with
head
down-
ward
in
cutting
off
the
limb.
After
severing
the
limb
the
adult
begins
to
oviposit.
The
eggs
are
laid
at
the
base
of
the
leaf
buds
and
usually
one
egg
is
deposited
at
a
place,
but
this
also
varies
and
sometimes
two
and
in
rare
cases
3
or
4
eggs
are
deposited
at
one
leaf
bud.
The
number
of
eggs
deposited
in
a
single
limb
varies
but
is
usually
from
8
to
12.
The
female
is
usually
accompanied
by
the
male
but
the
girdling
is
done
entirely
by
the
female.
Before
depositing
the
egg
she
makes
an
incision
with
the
mandibles
at
the
point
where
the
egg
is
to
be
depos-
ited.
After
this
incision
is
made
some
little
time
is
taken
to
hollow
out
a
place
between
the
bark
and
the
limb
in
which
to
place
the
egg.
This
hollowing
out
process
is
done
by
the
ovipositor.
After
this
is
com-
pleted
the
egg
is
deposited
and
the
opening
is
sealed
by
a
black
gluey-
like
substance
which
is
discharged
from
the
ovipositor.
Next
the
female
makes
a
great
number
of
small
transverse
incisions
below
the
point
where
the
egg
is
deposited
with
her
mandibles.
This
is
done
so
the
bark
in
drying
will
raise
like
a
blister
and
not
crush
the
egg.
Dur-
ing
the
period
in
which
she
is
depositing
the
eggs
the
female
often
ascends
to
the
end
of
the
branch
and
begins
feeding.
In
nearly
all
cases
observed
the
female
as
well
as
the
male
fed
entirely
on
the
tender
wood
at
the
base
of
the
leaf
buds
at
the
extremity
of
the
branch.
This
feeding
habit
is
not
confined
to
the
branches
on
which
she
is
ovipos-
iting
but
she
may
feed
on
other
branches
as
well.
The
method
of
girdling
varies
but
in
most
cases
the
cut
is
made
entirely
around
the
limb.
The
limb
is
seldom
entirely
severed
but
a
small
portion
of
the
center
is
left
intact.
The
weight
of
the
limb,
especially
if
the
tree
is
112
JOURNAL
OF
ECONOMIC
ENTOMOLOGY
[Vol.
9
still
in
leaf,
is
sufficient
to
break
off
the
limb
and
it
drops
to
the
ground.
The
egg
when
first
deposited
is
snowy
white
in
appearance,
is
oblong
in
shape
and
from
2.5
to
3
mm.
in
length,
averaging
2.75
mm.
INJURY
When
nurseries
are
adjacent
to
forests
the
damage
may
be
very
severe
and
the
greater
amount
of
damage
is
caused
by
beetles
which
have
migrated
from
other
trees
to
the
pecan.
Many
branches
are
severed
which
would
bear
nuts
the
succeeding
year.
In
the
nursery
row
small
trees
are
severed
near
the
ground
and
one
insect
may
do
a
surprisingly
great
damage
in
that
respect.
The
wounds
made
give
an
opportunity
for
fungous
diseases
to
enter
although
this
damage
in
our
observation
has
not
been
well
marked.
Some
damage
is
done
in
checking
the
growth
of
the
tree.
On
trees
whose
branches
are
to
be
used
as
wood
for
budding,
the
loss
is
very great
as
this
is
the
wood
which
is
usually
severed.
LIFE-HISTORY
The
first
females
begin
to
emerge
about
the
25th
of
August
and
they
continue
to
emerge
until
the
first
of
October.
After
turning
from
the
pupal
stage
they
remain
in
the
larval
burrow
for
from
2
to
10
days
and
then
emerge
by
eating
a
small
round
hole
through
the
limb.
From
12
to
29
days
after
the
female
emerges,
oviposition
commences
and
continues
in
those
cases
we
have
observed
until
the
female
dies.
The
number
of
eggs
deposited
varies
from
50
to
207
but
the
average
female
deposits
about
175.
Oviposition
is
begun
by
the
first
females
the
latter
part
of
September
and
continues
until
in
December.
The
greatest
infestation
occurs
from
the
12th
to
the
20th
of
October.
In
a
few
cases
the
females
have
lived
until
the
last
of
December
but
most
of
them
die
by
the
first
of
December.
The
first
freeze
kills
those
that
have
not
died
from
natural
causes.
The
females
live
from
42
to
84
days,
and
the
males
about
the
same
length
of
time.
The
eggs
hatch
in
from
17
to
30
days
after
they
are
deposited,
the
average
time
of
hatching
being
23
to
25
days.
The
larva
emerges
from
the
egg
by
eating
its
way
out
by
means
of
the
mandibles.
It
at
once
begins
to
hollow
out
a
small
cavity
in
the
branch
and
keeps
on
feeding
all
winter.
Several
larvae
may
develop
in
one
branch.
A
very
small
number
of
larvae
develop
in
proportion
to
the
number
of
eggs
that
are
laid
so
one
seldom
finds
more
than
three
or
four
larvae
in
a
girdled
twig.
The
larvae
burrow
in
the
girdled
twigs
until
the
following
summer,
the
larval
stage
lasting
from
288
to
328
days.
Before
pupating
the
February,
'16]
ENTOMOLOGISTS'
DISCUSSIONS
113
larvae
eat
a
great
number
of
small
holes
through
to
the
outside.
The
larval
burrow
is
also
stopped
with
grass
before
the
larva
pupates.
Pupation
takes
place
during
the
latter
part
of
August
and
the
first
part
of
September.
The
pupal
stage
lasts
from
12
to
14
days,
and
is
passed
in
the
larval
burrow.
CONTROL
METHODS
The
method
which
had
been
recommended
in
the
past,
that
of
gathering
up
the
fallen
twigs
and
burning
them
in
order
to
kill
the
larvae,
is
practicable
where
a
pecan
orchard
is
not
located
in
the
vicinity
of
other
trees.
When
forests
are
located
near
a
pecan
orchard
there
is
always
more
or
less
migration
from
other
trees
to
pecan
trees.
To
meet
such
conditions
we
tried
out
a
series
of
experiments
with
arsenate
of
lead
and
found
it
entirely
effectual.
PRESIDENT
GLENN
W.
HERRICK:
IS
there
any
discussion?
MR.
S.
J.
HUNTER:
I
would
like
to
ask
if
Mr.
Bilsing
noticed
any
tendency
of
the
female
ovipositing
at
the
base
of
the
minor
twigs?
In
the
case
of
the
elm
twig
girdler
they
invariably
select
the
base
of
the
twigs.
I
also
wish
to
ask
if
the
twig
falls
after
being
attacked
by
the
girdler?
MR.
S.
W.
BILSING:
Regarding
the
first
question
I
have
seen
females
oviposit
many
times
at
the
base
of
minor
twigs.
The
damage
is
very
much
less
to
older
trees
as
they
are
not
injured
to
any
great
extent
because
the
beetles
do
not
cut
off
enough
limbs
to
be
of
any
consequence.
Most
of
the
limbs
are
cut
two feet
from
the
trunks
of
the
smaller
trees,
and
they
are
usually
10
mm.
in
diameter.
As
a
rule
the
ovipositing
is
done
in
the
main
twigs.
Many
times
the
twig
falls
after
being
girdled
by
the
female
and
she
falls
with
it.
This
is
especially
so
in
windy
weather.
PRESIDENT
GLENN
W.
HERRICK:
Never
at
the
base?
MR.
S.
W.
BILSING:
Yes,
sometimes
they
deposit
eggs
at
the
base
of
the
twigs.
Occasionally
the
eggs
are
deposited
in
the
middle
of
the
twig.
MR.
W.
C.
O'KANE:
I
would
like
to
ask
if
Mr.
Bilsing
maintained
check
cages
in
his
experiment
where
other
individuals
were
similarly
confined,
but
without
access
to
sprayed
material?
In
other
words
did
the
specimens
all
die
because
of
eating
poison?
MR.
S.
W.
BILSING:
I
will
say
that
in
the
experiments
shown
in
the
chart
I
think
all
of
them
died
from
the
spray
material.
I
made
several
experiments
later
in
the
fall
but
could
not
consider
the
re-
sults
accurate
because
of
the
beetles
in
the
field
dying
under
the
8
114
JOURNAL
OF
ECONOMIC
ENTOMOLOGY
[Vol.
9
same
conditions,
but
I
think
all
the
beetles
in
the
cage
experiments
died
from
the
effects
of
the
arsenate
of
lead.
MR.
W.
C.
O'KANE:
The
question
in
my
mind
is
whether
some
of
the
insects
in
your
experiments
may
have
died
because
they
were
in
cages.
MR.
S.
W.
BILSING:
Where
the
beetles
died
in
confinement
they
were
in
cages.
Some
are
still
in
the
small
cages.
MR.
W.
C.
O'KANE:
How
large
are
the
cages?
MR.
S.
W.
BILSING:
We
carried
on
the
experiments
in
small
cages
which
were
about
18
inches
high,
on
the
life-history
of
the
insect,
and
checked
up
these
conditions
with
the
conditions
in
the
field.
All
of
the
beetles
that
were
confined
in
large
cages
were
dead
in
48
hours
and
a
part
of
them
in
16
hours.
Mn.
J.
L.
KING:
I
would
like
to
ask
if
all
these
beetles
were
of
one
sex?
MR.
S.
W.
BILSING:
I
used
both
males
and
females
in
confining
them
in
a
cage.
The
males
died
just
the
same
as
females.
Perhaps
the
males
did
not
feed
quite
as
much
as
the
females.
MR.
H.
A.
GOSSARD:
I
would
like
to
ask
how
the
schedule
for
spraying
pecans
fits
in
with
the
schedule
for
destroying
the
case
worm,
the
bud
worm
and
other
pecan
insects;
does
this
have
to
be
an
independent
spray?
MR.
S.
W.
BILSING:
I
have
never
done
any
work
on
the
case
worm
but
I
do
not
believe
it
would
fit
in.
MR.
C.
L.
METCALF:
These
experiments
have
been
intensely
interesting
to
me
because
of
the
parallelism
between
this
species
and
Oncideres
cingulata
in
North
Carolina.
I
would
like
to
ask
Mr.
Bilsing
if
he
made
any
experiments
to
indicate
the
most
favorable
conditions
for
passing
the
winter?
Whether
he
found
any
difference
in
the
percentage
of
those
that
live
through
the
winter
when
they
were
de-
pendent
on
dry
or
moist
conditions,
and
also
how
the
limb
was
girdled
when
the
twig
sloped
downward?
MR.
S.
W.
BILSING:
In
answering
the
first
question,
I
found
in
rearing
material
for
my
work,
moisture
had
a
great
deal
to
do
with
the
number
of
larvae
which
survived.
A
small
number
lived
over
in
the
limbs
which
remained
on
the
ground.
In
order
to
secure
sufficient
material
it
was
necessary
to
tie
a
great
number
of
these
branches
up
to
the
limbs
of
various
trees.
In
answering
the
second
question
I
will
state
I
have
never
observed
any
beetles
girdling
the
branches
which
sloped
downward.
MR.
R.
W.
LEIBY:
Have
you
noticed
any
egg
parasites?
MR.
S.
W.
BILSING:
No.
A
considerable
per
cent
of
these
insects
are
parasitized
by
a
tachinid
fly.
I
have
not
done
a
great
deal
of
work
on
this
but
I
expect
to
work
on
it
in
the
future.
February,
'16]
AINSLIE:
CRAMBID
NOTES
115
MR.
C.
L.
METCALF:
I
wonder
if
Mr.
Bilsing
would
care
to
tell
us
his
method
of
keeping
track
of
the
females
in
order
to
find
how
many
twigs
they
girdled.
MR.
S.
W.
BILSING:
My
work
along
that
line
has
not
been
very
satisfactory.
The
first
season
I
tried
to
keep
track
of
these
beetles
by
marking
them
with
red
and
black
ink
on
the
wing
covers.
This
was
rather
unsatisfactory.
In
order
to
determine
the
number
of
eggs
deposited
and
the
number
of
twigs
girdled
the
past
season,
I
followed
up
the
plan
of
caging
up
some
40
insects
in
small
cages
in
order
to
take
complete
notes
of
them.
I
found
that
the
data
collected
in
this
way
agreed
in
general
with
that
collected
in
outside
conditions.
MR.
C.
L.
METCALF:
Are
the
results
on
your
chart
all
from
laboratory
tests?
MR.
S.
W.
BILSING:
Yes,
all
the
data
on
my
chart
are
laboratory
tests.
PRESIDENT
GLENN
W.
HERRICK
:
I
will
now
call
for
a
paper
by
Mr.
George
G.
Ainslie.
NOTES
ON
CRAMBIDS
I
By
GEO.
G.
AINSLIE,
Entomological
Assistant,
Cereal
and
Forage
Insect
Investigations,
Bureau
of
Entomology,
U.
S.
Dept.
Agriculture
The
Crambithe
hold
much
the
same
position
economically
as
cut-
worms,
jassids
and
aphids.
Like
the
poor
they
are
always
with
us,
and,
though
the
injury
they
do
is
usually
clandestine
and
unobserved,
it
is
none
the
less
real.
Everyone
interested
in
insects
is
familiar
with
the
small
whitish
moths
which
in
almost
every
locality,
at
some
season
of
the
year,
swarm
so
thickly
in
the
grass,
but
the
larvae
of
these
same
moths
are
so
successful
in
concealing
themselves
that
even
some
ento-
mologists
with
considerable
field
experience
are
unacquainted
with
them.
Very
little
has
been
published
concerning
their
habits
or
from
an
economic
standpoint.
We
are
convinced,
however,
from
our
field
work
in
Tennessee
and
neighboring
states,
as
well
as
from
material
and
reports
of
damage
received
from
field
men
of
the
Bureau
in
other
parts
of
the
country,
that
the
various
species
belonging
to
this
family
cause
widespread
damage
every
year.
Two
years
ago
we
undertook
an
extended
study
of
the
group
and
it
is
with
the
hope
of
stimulating
interest
in
these
insects
and
obtaining
records
from
a
wider
area
that
these
brief
notes
are
presented.
In
his
catalog
in
1902,
Dr.
Dyar
records
79
species
of
the
subfamily
Crambinm
from
North
America.
Since
then
several
new
species
have
been
described,
so
the
number
now
recorded
from
North
America
is
I
Published
by
permission
of
the
Secretary
of
Agriculture.