EVALUATION OF SOME PLANTS FOR THEIR INSECTICIDAL PROPERTIES AGAINST IMPORTANT LEPIDOPTEROUS PESTS
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Date
2015
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CSK Himachal Pradesh Krishi Vishavavidyalaya, Palampur
Abstract
Four different plants viz., Acorus calamus L., Vitex negundo L., Adhatoda vaisca L.
and Dioscorea deltoidea Wall. were evaluated for their biological activities against Plutella
xylostella (L.) and Helicoverpa armigera (Hub). Four different solvents viz., methanol, hexane,
ethyl acetate and aqueous extracts were used for extraction. LC50 values for methanol, ethyl
acetate, hexane extract of A. calamus, methanol extract of V. negundo and ethyl acetate extract
of A. vasica were 2.0203, 2.2938, 2.8474, 3.4600 and 4.1709 per cent for IInd instar larvae of P.
xylostella, respectively. For H. armigera, LC50 values were 1.7495, 2.3296, 3.0859, 3.7773 and
4.0296 per cent for methanol, ethyl acetate, hexane extract of A. calamus, methanol extract of A.
vaisca and ethyl acetate extract of V. negundo for IInd instar larvae of H. armigera. Different plant
extracts also exhibited ovicidal asctivity against P. xylostella and H. armigera and resulted in
12.62 to 79.39 and 12.74 to 53.61 per cent reduction in egg hatching, respectively. Plant extracts
from polar solevents were found to be more effective in reducing the hatchability as compared to
non-polar. Maximum antifeedant activity (74.63 and 80.95% feeding inhibition) was observed in
hexane and methanol extract of A. calamus for P. xylostella and H. armigera, respectively.
Repellent effects showed that maximum repellency was observed in methanol extract of A.
calamus (51.33%) and ethyl acetate extract of V. negundo (56.89%) for P. xylostella and H.
armigera, respectively. Influences of the exposure of immature stages of P. xylostella and H.
armigera to sub-lethal concentartion of different plant extracts resulted in increased duration of
total developmental period of P. xylostella and H. armigera as compred to untreated check.
However, per cent survival upto adult formation was decreased considerably. Morphogentic
abnormalities in different developmental stages such as lack of melanization in larval and pupal
stages, pupal-adult intermediate, folded wing or wing less adults were also observed. Lower
values for Total growth index (TGI) for P. xylostella were observed, which varied from 1.74 to
6.39 as compared to 7.16 to 13.42 in untreated check. Similar results indicating low TGI were
obtained in H. armigera. Adults emerging from treated larvae in both test insects reflected
reduction in fecundity as compared to those emerging from untreated larvae. However, there was
non-significant effect on the fertility of the test insects. In free choice test for recording oviposition
deterrent activity against P. xylostella and H. armigera, low to moderate level of deterrence was
evident (13.00 to 38.22%) and (13.67 to 36.29%), respectively. Field efficacy of different plant
extracts revealed that hexane extract of A. calamus was most effective against H. armigera and
methanol extract of A. calamus against P. xylostella and resulted in 48.91 and 55.51 per cent
reduction in population after second round of spray, respectively.
Description
Doctoral Dissertation
Keywords
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