POPULATION DYNAMICS, VARIETAL SCREENING AND MANAGEMENT OF THRIPS, Thrips tabaci Lindeman INFESTING Bt COTTON 2915
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Date
2019-08
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JAU, JUNAGADH
Abstract
Investigations on population dynamics, varietal screening and management of
thrips, Thrips tabaci Lindeman infesting Bt cotton were carried out under field
condition during Kharif 2018 at Junagadh Agricultural University, Junagadh. For the
management of thrips, different ten varieties /genotypes were screened and different
combinations of nitrogenous fertilizer doses and soil as well as foliar application of
insecticides were evaluated.
The incidence of thrips, T. tabaci was commenced from 3
rd week of July and
continued till third week of November having a single peak (27.96 thrips /three
leaves) during 3rd week of August. Thrips population had negative significant impact
due to maximum temperature [r = -0.570*] and significant positive correlation to
rainfall [0.768*], morning relative humidity [0.562*] as well as evening relative
humidity [0.574*]. Bright sunshine hours were negatively, wind speed, and minimum
temperature were positively correlated with the incidence of thrips population but
results were not significant.
The lowest thrips incidence was recorded in GJHV-541 (3.57 thrips /3 leaves)
and GJHV-540 (4.41) genotypes of Bt cotton and was categorized as resistant (R).
The highest thrips population was recorded in G.Cot.-460 (11.84), G.Cot.-18 (12.40)
and G.Cot.-12 (13.55) variety and it was categorised into susceptible (S) against the
pest.….....………….……………………………………………………….………….Abstract
Based on both the sprays and pooled over periods, thrips can be effectively
managed by nitrogenous fertilizer application of 240 kg /ha and soil and foliar
application of fipronil 0.3 G + spinetoram 11.7 SC. Interaction of fertilizer to
insecticidal application was found effective in treatment combination [(240 kg N /ha)
+ (fipronil 0.3 G + spinetoram 11.7 SC)] followed by [(240 kg N /ha) + (carbofuran 3
G + spinetoram 11.7 SC)]. While, [(360 kg N /ha) + (fipronil 0.3 G + spinosad 45
SC)] and [(360 kg N /ha) + (carbofuran 3 G + spinosad 45 SC)] treatments performed
less in giving satisfactory protection to Bt cotton crop against thrips.
The highest {2906 kg /ha} seed yield was harvested in the plots treated with
[(240 kg N /ha) + (fipronil 0.3 G + spinetoram 11.7 SC)] followed by [(240 kg N /ha)
+ (carbofuran 3 G + spinetoram 11.7 SC)] {2831}. As far as the per cent increase of
yield over control concerned, maximum yield loss can be avoided with spray
application of [(240 kg N /ha) + (fipronil 0.3 G + spinetoram 11.7 SC)] {92.09},
followed by [(240 kg N /ha) + (carbofuran 3 G + spinetoram 11.7 SC)], [(300 kg N
/ha) + (fipronil 0.3 G + spinetoram 11.7 SC)], [(240 kg N /ha) + (fipronil 0.3 G +
spinosad 45 SC)] and [(240 kg N /ha)+ (carbofuran 3 G + spinosad 45 SC)].
The highest Incremental Cost Benefit Ratio (ICBR) was calculated from the
plots treated with [(240 kg N /ha) + (fipronil 0.3 G + spinosad 45 SC)]. But in overall
effectiveness of nitrogenous fertilizer and insecticides application [(240 kg N /ha) +
(fipronil 0.3 G + spinetoram 11.7 SC)] found most effective (first rank) followed by
N1I1 [(240 kg N /ha) + (carbofuran 3 G + spinetoram 11.7 SC)] > N1I4 [(240 kg N /ha)
+ (fipronil 0.3 G + spinosad 45 SC)] > N2I2 [(300 kg N /ha) + (fipronil 0.3 G +
spinetoram 11.7 SC)] > N2I4 [(300 kg N /ha) + (fipronil 0.3 G + spinosad 45 SC)] >
N2I3 [(300 kg N /ha) + (carbofuran 3 G + spinosad 45 SC)] > N2I1 [(300 kg N /ha) +
(carbofuran 3 G + spinetoram 11.7 SC)] > N1I3 [(240 kg N /ha) + (carbofuran 3 G +
spinosad 45 SC)] > N3I4 [(360 kg N /ha) + (fipronil 0.3 G + spinosad 45 SC)] > N3I1
[(360 kg N /ha) + (carbofuran 3 G + spinetoram 11.7 SC)] > N3I2 [(360 kg N /ha) +
(fipronil 0.3 G + spinetoram 11.7 SC)} and N3I3 [(360 kg N /ha) + carbofuran 3 G +
spinosad 45 SC)] against T. tabaci.