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IMPACT OF BOLLGARD II Bt COTTON ON BIOLOGICAL PARAMETERS OF Spodoptera litura (Fab.)

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Title IMPACT OF BOLLGARD II Bt COTTON ON BIOLOGICAL PARAMETERS OF Spodoptera litura (Fab.)
 
Creator PRADEEP, POTANAPALLI
 
Contributor DURGA PRASAD, N.V.V.S.
 
Subject BOLLGARD II, Bt COTTON, Spodoptera litura (Fab.)
 
Description A field experiment was conducted at Regional Agricultural Research
Station, Lam, Guntur during kharif, 2010 to carryout the “Impact of Bollgard II
Bt cotton on biological parameters of Spodoptera litura (Fab.)”. In the
investigations monitoring of S. litura through pheromone traps, performance of
cotton hybrids containing Cry1Ac (BG I) and Cry1Ac+Cry2Ab (BG II) of Tulasi-
9, Mallika and their corresponding non Bt versions on the survival of S. litura
larval stages in the field conditions and the effect of Cry1Ac+Cry2Ab (purified
protein) larval diet on the mortality of larva in the laboratory were studied.
At the time of sowing of cotton crop, the initial incidence of S. litura was
32.50 moths/trap/week in 34th standard week (third week of August). There after
there was decline in moth catches in succeeding weeks due to high amount of
rainfall received during the corresponding weeks. The peak moth incidence was
observed at 6th standard week (first week of February) with 157.50 moths
/trap/week and during this period low minimum temperature was observed. High
moth catches were recorded from January to first fortnight of February (102.00 to
157.50 moths/trap/week) when minimum temperature and evening relative
humidity are low, however there were wide fluctuations in moth catches.
The correlation between the moth catches and minimum temperature was
negative and significant, whereas sunshine hours showed positive and significant
influence on moth catches. The cumulative effect of all the weather parameters
were non significant and together accounted for 62.00 per cent of total variation
(R2 = 0.62) on the moth catches.
The mortality of 1st and 2nd instar larvae of S. litura was high with
reduced mortality rates in 3rd and 4th instar larvae on BG II hybrids, where as the
mortality was very low and more or less similar in BG I and non Bt cotton
hybrids. The BG II cotton hybrids were found promising at 40 and 70 days
inflicting high larval mortality compared to 100 and 130 days old crop. This
might be due to high level expression of dual toxin at vegetative stages of the
crop compared to reproductive stages of the crop. The survival of early larval
instars of S. litura was very low than the later instars on the leaves of both the
BG II cotton hybrids and the 1st instar larvae showed highest mortality compared
to 2nd instar larvae. The survival rate of 3rd instar larvae was higher and recorded
only 50 per cent mortality, whereas the influence of BG II hybrids on grown up
4 th instar larvae was very minimal and equal to BG II and non Bt hybrids at 130
DAS.
The mean weight of larva fed on BG II cotton leaves was found to be very
low. The weight reduction of late instars of S. litura was lower than the early
instars on the leaves of both the BG II versions at all stages of the crop, whereas
BG I and non Bt versions did not effect the larval or pupal weight and weight
gains were more or less similar through out the crop season.
The mean leaf area consumed by 1st instar larvae of S. litura on BG II
cotton hybrids were found to be significantly very low at 40 & 70 DAS due to
higher mortality rates and the same trend was also observed in 2 nd instar larvae.
The mean leaf area consumption by 3 rd & 4 th instar larvae of S. litura were
higher at all the stages of the crop as the larvae were not effected by BG II
hybrids leading to considerable damage of the crop. In BG I and non Bt hybrids
the leaf area consumption was very high for all the instars during the entire crop
period.
In the diet incorporation bioassay studies, the highest concentration of
96.00 μg/ml tested showed corrected mean mortality of 66.67 per cent in 1st
instar larvae, whereas same concentration was able to record only 36.67 per cent
in 2nd instar larvae and there was no influence of this concentration on 4th instar
larvae recording zero per cent mortality at 72 hours after feeding.
 
Date 2016-06-06T09:54:38Z
2016-06-06T09:54:38Z
2011
 
Type Thesis
 
Identifier http://krishikosh.egranth.ac.in/handle/1/66798
 
Language en
 
Relation D9043;
 
Format application/pdf
 
Publisher ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY