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One of the most important aspects of agriculture is pest management. Pesticides
used in the past produced a variety of environmental problems, including ecological
imbalances, soil fertility loss, and marine life degradation. Conventional pesticides have
also been linked to a number of significant and detrimental effects on human and animal
health, including severe malignancies, neurological diseases, hormone disruptions, and
reproductive troubles. Botanical pesticides are found to be an effective alternative to
conventional pesticides for pest management. Sphagneticola trilobata (L.) Pruski, is an
herb included in the Asteraceae and is well known for its medicinal properties, information
about its bioactivity against insects is very less. Hence, in this study we evaluated the
antifeedant and growth regulatory activity of various extract of Sphagneticola trilobata
against Spodoptera litura.
Dried and powdered S. trilobata plant materials were sequentially extracted with
hexane and methanol followed by concentrated in vacuo in a rotary evaporator at a lower
temperature to obtain crude extracts of S. trilobata. Hexane extracts of aerial parts and roots
were named as SP1 and SP3 and methanol extract of aerial parts and roots were named as
SP2 and SP4. The yield of methanol extract of aerial parts (5.67% w/w) was higher
followed by methanol extract of roots (2.32% w/w), hexane extract of aerial parts (1.96%
w/w) and hexane extract of roots (1.23% w/w)
The antifeedant activity of various extracts of Sphagneticola trilobata tested in nochoice
leaf disc bioassay revealed that methanol extract of aerial parts of S. trilobata had
the maximum antifeedant activity of 52.10 per cent at 0.1 per cent of the extract against S.
litura after 24h of feeding. Compared to aerial extracts, root extracts were less active
against S. litura. At lower concentrations, the antifeedant activity of all the extract were not
much prominent and are not statistically significant. The antifeedant activity of all the
extract increased in 48h experiment except for 0.1 per cent concentration. The decreasing
order of antifeedancy of four extracts was SP2>SP1>SP4>SP3.
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Similar results were recorded in the choice method of bioassay of extracts against
S. litura. Maximum antifeedant activity of 46.65 per cent was obtained for methanol extract
of aerial parts (SP2) after 24h of feeding. At lowest concentrations of 0.005, 0.01 and 0.03
per cent none of the extracts exhibited significant difference in activity. Increasing
concentration beyond 0.03 per cent had a significant effect on antifeedancy in the choice
method. As similar to the no-choice method, reduced activity was recorded after 48h of
feeding. Maximum antifeedant activity of 38.81 per cent was recorded for SP2 after 48h of
feeding. Similar to the no-choice method, root extracts exhibited a low level of activity
against S. litura.
Insect growth regulatory activity of various extracts was evaluated by diet
incorporation method against five-day old larvae of S. litura. A maximum larval weight
reduction of 31.4 per cent was recorded for SP4 at 0.1 per cent of the extract. A significant
increase in larval duration compared to control was recorded for SP2 extracts at higher
concentrations. Similar to larval weight reduction, a dose-dependent pupal weight
reduction was recorded for SP1 (29.57 per cent at 0.1 per cent of the extract). Compared to
the other three extracts, pupal weight reduction was very less for SP3. Pupal duration
increased to a maximum period of 13.54 days at 0.1 per cent of SP4. Observations on
abnormal pupae were not significant for any of the extracts. No larval mortality could be
obtained with any of the treatments. A maximum of 16.7 per cent larval pupal intermediates
was recorded for SP4 at the highest dose, but it was not significantly different from other
treatments. Similar to larval mortality, no pupal adult intermediates were recorded for any
of the extracts. Maximum pupal mortality of 41.00 per cent was recorded at 0.1 per cent of
SP1, and it was significantly different from other treatments. For all the extracts, pupal
mortality was dose-dependent. Minimum adult emergence was noticed for SP1 at 0.1 per
cent of the extract.
GC-MS/MS and LC-MS/MS analysis of active fractions revealed that more
phytochemicals are present in aerial parts than roots. The higher activity of aerial parts
might be due to the presence bioactive compounds like andrographolide, artemisin,
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genistein and taxifolin. Most of the chemicals identified were derivatives of steroids,
terpenoids and flavonoids.
The study results indicate that methanol extract of aerial parts of S. trilobata has
strong antifeedant activity against S. litura. All other extracts were relatively less active
against S. litura. Insect growth regulatory activity was maximum for hexane extract of
aerial parts. All the extracts adversely affected the growth and devolvement of S. litura.
The absence of larval mortality indicates that all the extracts have less contact toxicity.

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