International Journal of Horticulture 2015, Vol. 5, No.16, 1
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grain were shifted to plastic rearing jar (15x20 cm),and
were maintained in the laboratory at average conditions
of 24±6
ο
C, 65±10% RH and 16:8 (L: D) for 20-25
days until adults emerged.
Regular collections of emerged moths into oviposition
jar (10x15 cm) with mesh (30-40 pore size) at the bottom
were made. The jar was placed over the corn flour in a
metal/plastic tray for egg laying for 24 h.
Subsequently, the host eggs were collected by sieving
the flour, and were used for the rearing and in
experiments.
2.2 Rearing of
Trichogramma chilonis
(Ishii) on
S.
cerealella
Approximately 1000-1300 fresh host eggs were glued
to paper card (5x8 cm), and card was allowed to dry
for 1-2 hrs. Subsequently, the dried card was exposed
to parasitism for 24 h. in glass jars (5x12 cm)
containing approximately 30 to 40 adults
(mixed-gender) of
T. chilonis
, under the lamp light.
The likely parasitized card was removed and was
transferred to another glass jar of the same size, and
was incubated at the 23±3
ο
C, 70±10% RH and 14:10
(L: D) conditions until adult emerged. The stock
culture of
T. chilonis
was maintained and was used in
the subsequent experiments
2.3 Preparation of different concentrations of
pesticides solution
Commercially available fipronil was diluted with tap
water to prepare stock solution of field recommended
dose(x = 480 ml/acre) under the aforementioned
laboratory conditions. The stock solution was diluted
(serial
dilutions)
and
five
different
concentrations including 0.4x, 0.2x, 0.08x, 0.04x,
and 0.02x of insecticide were prepared for use in the
experiments by the formula: C
1
V
1
= C
2
V
2,
where C
1
and V
1
are the concentration and volume of commercial
pesticides/ stock solution, respectively, while C
2
and
V
2
are the concentration and volume of the required
pesticide solutions (diluted), respectively.
2.4 Testing of pesticides against larval and pupal
stages of
T. chilonis
Approximately 200-300 fresh
S. cerealella
eggs card
was exposed for 24 hours to parasitoids in glass jars
(5x12 cm) containing approximately 14 to 20
mixed-gender adults of
T. chilonis
under
aforementioned laboratory conditions. The likely
parasitized card was subsequently removed and was
incubated under conditioned mentioned earlier until
larvae (three days old parasitized) and pupae (six days
old parasitized) were formed, followed by the card
was removed, and was cut to small card strips
(approximately 0.8 x 8 cm), each containing 10-15
host
eggs,
prepared
separately
for
each
aforementioned doses. For larval testing, three days
(72 h), while for pupal stage treatment six days (144 h)
old parasitized cards were dipped for 1-2 seconds in
the pesticide solution or in water (untreated: control)
of each treatments (stage). The trial was replicated 10
times for each stage, in order to assess dose-wise
and stage-wise effects of pesticides on
T. chilonis
regarding emergence. Subsequently card was removed
and air dried at room temperature for 1 h. and was
transferred into a vial (1x10 cm). The cards were
incubated at aforementioned controlled conditions
until adult emerged.
The number of pupae of the pesticides dipped card,
and the number of the specimens emerged from the
pupae were determined by magnifying lens without
dissecting them (generally one
T. chilonis
adult
emerged from single parasitized
S. cerealella
egg),
and recorded separately for each concentration and
stage treated with pesticide.
2.5 Testing the pesticides to assess parasitism by
T.
chilonis
Approximately 100 to 175 fresh
S. cerealella
eggs
were glued on hard paper card (5x8 cm), and was
dried, and subsequently cut into 10 strips (0.9x8 cm
each) each containing approximately 20-35 host
eggs, and were followed dipped for 1-2 seconds in
the solution of each of aforementioned doses in
addition to water. The cards were dried, and were
transferred to a glass vial (1x10 cm) containing one
pair of
T. chilonis
(< 24 h old) for 24 h for completion
of parasitization of previously treated host eggs.
The females were removed and the vials were
incubated at aforementioned conditions until pupae
formation. The data were recorded by counting pupae
after 7 days of exposure to parasitoids.
2.6 Data Analysis
The recorded data were analyzed using general linear
model (Statistix 9) on percent emergence as well as
average parasitization. Mean separation was carried
out by Tukey HSD test (P = 0.05). Reduction in
