Study on Population Dynamics of Okra Shoot and fruit Borer (Eariar spp.) and Biology of Chelonus Blackburni Cameron
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Date
1993-10
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Entomology Department, N. M. College of Agriculture Gujarat Agricultural University, Navsari
Abstract
In the study of biology of Chelonus blackburni
Cameron on rice moth (Corcyra cephalonica Stainton) , it was
found that the egg was minute, white and arcuate with both
ends round. It measured on an average 0.114 + 0.015 mm
in length and 0.059 ~ 0.011 mm in breadth. The average
incubation period was 17.94 + 2.38 hours with hatching
percentage as 95.26. The larvae passed through five instars .
The developmental periods of first, second , third, fourth
and fifth larval instar ranged from 42 to 66, 72 to 96, 72
to 96, 96 to 120 and 72 to 96 hours, respectively. Total
larval period ranged from 354 to 378 hours . The full grown
larvae measured on an average 2.749 ~ 0.507 mm in length and
1.159 ~ 0.072 mm in breadth. Pupation took place inside t he
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h.o~ cocoon. The newly formed pupa was whitish yellow • In
colour which turned to black later on . The pupa measured on
an average 3.552 ± 0.562 mm in length and 1.485 + 0.239 mm
in breadth. The pupal period lasted for on an average 12 . 44
± 2.52 days. The adult was black, highly sclerotized wi t h
dark brown st i gma in middle of the fore-wings. With expanded
wings the female measured on an average 7.437 ± 0.615 mm
whereas the male measured on an average 6.546 ± 0.600 mm.
The average pre-oviposition, oViposition and postoviposition
periods lasted for 0, 14.2 ± 1.61 and 0.3 days,
respectively. The sex-ratio of male:female was 1:0.81. The
average fecundity was 295.7 ± 16.89 eggs.
In the study of population dynamics of okra shoo t
and fruit borer (Earias spp.), infestation of Earias spp. on
shoots J fruits and plants were the lowest in months of
September, July and July, respective ly. Study on influence
of sowing date on infestation of Earias spp. showed that the
infestation was the lowest in the month of August on shoots
and in the months of May and June on fruits and plants . In
relation to age of crop, the infestation of Earias spp. on
shoots was the highest (20.0%) on five weeks old crop. The
infestation in the fruits was the lowest (9.61%) in 6 weeks
old crop which reached to its maximum (65.35%) in crop with
11 weeks age and thereafter it declined in 12, 13 and 14
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weeks old orop. Considering the plant as a whol e the
Infestation was the lowest on 6 weeks old c rop. The
proportion of unmarketabl e fruits were the highest in the
crop Bown in the month 01 December whereas it was the lowest
In June sown crop. The larval population ranged f rom 0.28 to
1.98 larvae pe r plant during the whol e year .
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The influence of weathe r parameters, viz . . maximum
temperature, minimum temperature, average temperature ,
morning r e lative humidity, evening relative humidi ty,
average relative humidity, sunshine hours, rainfall and
rainy days on larval population of okra shoot and fruit
borer CEarias spp.) was studied and correlation coefficient
and multiple regression were worked out. No parasite or
predator was found attacking Earias spp. during the study .
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Citation
PRAVINKUMAR DEVJIBHAI GHOGHARI_28999