Studies on the feeding potential of the coccinellid predator Pharoscymnus horni, Wesmael on the scale insect of sugarcane


Rao, C.S.; Rao, C.S.

Indian Sugar 31(6): 401-403

1981


Pharoscymnus horni (Weise) is an efficient predator of Melanaspis glomerata (Green), an important pest of sugar-cane in Andhra Pradesh, India. Laboratory studies there showed that the adults consumed up to an average of 42.68 adult scale insects/day (1710 throughout the adult life of the beetle) or 90.43 crawlers/day. Beetle larvae consumed an average of 24.05 scale insects/day (217 in the course of development) or 187 crawlers/day. When adults were provided with an artificial diet containing honey, sugar and agar, together with 5-20% by weight of scale-insects, the life-span averaged 11-13 days, as compared with 11 days for the diet without insects and 30 days on sugar-cane. None of the females oviposited when provided with the artifical diets, though they did so readily when transferred to sugar-cane infested with M. glomerata.

September,
198
INDIAN
SUGAR
401
Sugarcane
and
its
Problems
Studies
on
the
Feeding
potential
of
the
coccinellid
Predator,
Pharoscymnus
Horni,
Wesmael
on
the
scale
insect
of
sugarcane'
By
t
C.
Sesbagiri
Rao
and
C.
Sabba
Rao
2
ABSTRACT
Pharoscymnus
horni,
Wesmael
is
an
efficient
predator
i
keeping
the
scale
insect
Melanaspis
glomerata,
Green
under
control.
Among
the
biological
factors
food
pla'.s
a
vital
role
in
its
life.
The
results
of
a
study
on
the
different
diets
tried
are
presented
in
this
paper.
They
indicated
that
Honey
agar
media
+
10%
by
weight
of
scale
proved
to
be
better
for
the
predator
in
increasing
its
life
span.
However,
it
failed
to
lay
eggs
till
it
was
provided
its
natural
diet
containing
100
per-cent
of
scale.
Introduction
Scale
insect
Melanaspis
glomerata
Green
is
a
serious
pest
on
sugarcane
causing
extensive
damage
in
quantity
and
quality
of
cane.
It
is
attacked
by
an
arroy
of
natural
enemirs
in
the
field
among
which
a
coccinellid
predator
P.
horni
was
found
to
be
very
effective
in
keeping
the
pest
under
check
by
devouring
them
in
different
stages.
Hence
a
detailed
study
was
made
to
find
out
the
feeding
potential
and
thereby
the
efficacy
of
the
predator
in
the
biological
control
of
the
scale.
Anonymous
(1972)
reported
that
P.
horni
was
found
to
be
very
active
and
voraciously
feeding
on
sugarcane
scale
insect
and
had
become
well
establish-
ed
in
Andhra
Pradesh.
Maieriais
and
Methods
Feeding
potential
of
axdult/grub
was
determined
by
keeping
them
individually
in
a
glass
jar,
of
18.5
cm
X
10cm
size
with
closed
bottom
and
open
at
the
top
end.
The
open
end
was
covered
with
a
thin
muslin
cloth.
In
feeding
trials,
six
larvae
and
adults
were
taken
for
evolution.
Observations
were
also
made
to
assess
the
feeding
potential
of
adult
beetles
on
the
scale.
Predators
were
given
a
predetermined
number
of
scales
to
feed
on.
It
was
ensured
that
the
number
of
scales
on
sugarcane
bit
introduced
into
glass
jars
at
about
the
same
time,
each
day,
were
always
more
than
the
predator
could
consume
and
the
counts
were
made
at
the
corresponding
time,
the
following
day.
1.
Part
of
the
thesis
submitted
by
the
sensor
author
for
award
of
M.
Sc
(Ag)
2.
Asst.
Dir.
of
Agriculture
(Sub.
Development)
Biological
control
laboratory,
Nidadavole
and
Entomologist,
(Ecolo,:y)
Agricultural
Research
Station,
Warangal.
402
INDIAN
SUGAR
September,
19
1
Similar
studies
were
made
with
crawlers.
The
feeding
potential
was
determined
by
confirming
the
individual
into
a
7.5cm
x
2.5cm
glass
vial
with
tight
muslin
covering
at
the
open
end.
Honey
agar
media
containing
the
following
ingre-
dients
was
used.
Water
100
c.
c.
Agar
Powder
1
gm
Sugar
20
gm
Honey
40
c.
c.
The
media
was
used
with
scale
insect
at
5%,
10%,
15%
and
20%
weight
of
the
diet.
Results
and
Discussion
The
beetles
were
found
to
feed
by
lifting
the
pygi-
dium,
loosening
it
with
its
labrum.
They
fed
on
soft
tissues
of
scale
insect
while
in
case
of
crawlers
they
were
wholly
eaten
away.
In
respect
of
grubs,
they
were
found
to
feed
on
scale
insect
by
chewing
holes
on
scale
armours.
Feeding
Potential
of
adults,
grubs
on
crawlers
and
scales
No.
of
repli-
Feeding
No.
of
No.
of
Feeding
No.
of
No.
of
cations
period
scales
crawlers
period
scales
crawlers
days
consumed
consumed
consumed
consumed
per
beetle
per
beetle
per
grub
per
grub
1st
10
431
996
9
210
1920
2nd
10
428
850
9
252
2060
3rd
10
432
885
9
198
1380
4th
10
420
830
9
182
1760
5th
10.
410
975
9
234
1470
6th
10
440
890
9
223
1520
Average
10
426.83
904.33
216.5
'1685
Averageftl
ny
42.68
90.43
24.05
187.16
Adult
of
P.
horni
had
a
maximum
daily
consump-
24.05
scales/day
with
a
total
of
217
crawlers
in
its
tion
of
42.68
scale/adult
with
a
total
consumption
of
grub
stage.
The
rate
of
feeding
declined
at
moulting
427
scales
in
a
period
of
10
days.
Thus,
an
adult
time.
beetle
was
estimated
to
consume
on
an
average
about
710
scale
insects
during
its
iife
span.
The
feeding
potential
increased
at
the
time
of
oviposition
while
it
reduced
at
mating
period.
Similarly
adult
beetles
consumed
on
an
average,
90.43
crawlers/day.
The
grub
of
this
species
devoured
on
an
average
The
grub
consumed
on
an
average
187
crawlers/
41
Different
experimental
diets
were
formulated
for
P.
horni
out
of
them
Honey-Agar
media
-I-
Scale
insect
proved
to
be
superior.
day.
Seprember,
1981
INDIAN
SUGAR
403
Different
Artificial
Diets
formulated
and
used
in
the
Experiment
are
as
follows
:
Diet
Longevity
days
1.
Honey
Agar
media
11
(9-12)
2.
Scale
insect
on
sugarcane
30
(28-35)
3.
Honey
Agar
media
-1-
5%
weight
of
scale
13
(12.16)
Honey
Aear
media
-I-
10%
weight
of
scale
12
(11-14)
Honey
Aear
media
+
15%
wei-
ght
of
scale
12
(10-13)
.
Honey
Agar
media
+
20%
wei-
ght
of
scale
11
(8.12)
are
in
confirmity
with
those
of
Sundby
(1968)
who
showed
that
addition
of
natural
food
to
synthetic
diets
improved
adult
longevity.
Summary
Honey
Agar
media
was
tried
as
a
basic
diet
and
scale insect
at
different
proportions
was
added
to
the
diet.
Among
the
different
diets
tried,
non
was
suitable
for
oviposition.
although
among
artificial
diets
honey
agar
media
+
10%
scale
insect
was
found
to
be
better
for
increasing
the
longevity
of
the
predator.
References
Anonymous
1972-73
:
Annual
progress
report
of
the
S.
R.
S.,
Anaka-
palli,
(A.
P.)
Adults
were
found
to
feed
readily
on
Honey
Agar
Media.
Adults
lived
on
an
average
for
11
days.
However
they
failed
to
lay
eggs.
When
5%
weight
of
scale
was
added
to
Honey
Agar
Media,
they
survived
for
12.16,
but
failed
to
ovi-
posit.
Marked
differences
were
not
noticed
in
the
longevity
by
increasing
the
weight
of
scale
to
diet
when
compared
to
the
second
diet.
In
all
the
artificial
diets
it
was
observed
that
when
the
predatory
beetles
were
transferred
to
scale
infested
cane
bits,
they
laid
eggs
readily.
It
may
be
inferred
that
the
predator
readily
accepted
alternate
food
which
served
only
as
a
source
of
energy
but
did
not
allow
development.
These
are
in
agreement
with
Smith
(1965)
and
Hodek
(1967).
When
natural
food
(scale
insect)
was
added,
the
adult
longevity
improved
considerably.
This
improve-
ment
was
apparently
due
to
addition
of
scale
insect
which
formed
a
rich
source.ofprojiep.
These
findings
Hodek,
I
1967:
Smith,
B.
C.
1965
:
Sund
by,
R.
A.
1968
:
Bionomics
and
ecology
of
predaceous
coccinel-
lidae
:
Ann.
Rev.
Ent.
Vol
12.
Effect
of
food
on
the
longevity
fecundity
and
development
of
adults
coccinellids
(Coleop-
tera)
:
Coccinellids.
Canod.
En-
tomologist
97
(9)
910-
919.
Some
factors
influencing
the
reproduction
and
longevity
of
Coccinella
septumpunctatal
(Col:
Coccinellidae).
Ento-
mophaga
13
(3)
pp.
197-
202.