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Biological Activity of Different Plant Extracts with Particular reference to their Insecticidal,Hormonal and Antifee ding Actions
Twenty locally available plants were screened for their antifeedant activity against three important crop pests of Kerala using water, acetone, benzene and petroleum other as extractants. Benzene was, in general, the best extractant and as a test insect H. vigintioctopunctata was more sensitive than...
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| Format: | Ph.D Thesis |
| Language: | Undetermined |
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Vellayani
Department of Entomology, College of Agriculture
1989
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| 100 | |a Saradamma K | ||
| 245 | |a Biological Activity of Different Plant Extracts with Particular reference to their Insecticidal,Hormonal and Antifee ding Actions | ||
| 260 | |a Vellayani |b Department of Entomology, College of Agriculture |c 1989 | ||
| 502 | |b PhD | ||
| 520 | 3 | |a Twenty locally available plants were screened for their antifeedant activity against three important crop pests of Kerala using water, acetone, benzene and petroleum other as extractants. Benzene was, in general, the best extractant and as a test insect H. vigintioctopunctata was more sensitive than S. litura or P. ricini. Among the twenty plants screened all the extracts of C. infortunatum, A.indica, T.neriifolia and E.odoratum and benzene and ether extracts of N.oleander gave high leaf protection against H.vigintioctopunctata. Against S.litura benzene and ether extracts of C.infortunatum, A.indica, T.neriifolia and N.oleander were effective. Water extract of E.odoratum and acetone extract of C.infortunaturm, A.indica and T.neriifolia also had high antifeedant activity against S.litura. All extracts of A.indica and water, benzene and acetone extract of N.oleander had antifeedant effect on P.ricini. High larval starvation was caused by most of the plant extracts which showed antifeedant action. But some extracts ineffective as antifeedant also caused high larval starvation. Eight essential oils obtained from the country were screened for feeding deterrency against P.ricini. Citronella oil, geranium oil and camphor oil gave significant protection, but the dosages required were too high to indicate possibilities of practical exploitation of essential oils as antifeedants for pest control. Based on PC 95 values worked out through bioassay studies using H.vigintioctopunctat as test insect N.oleander ranked first as antifeedant. It was followed by C.infortunatum, A.indica, T.neriifolia and N.odoratum. Based on larval starvation these plants had different ranking. Antifeedant activity of the extracts of T.neriifolia and N.oleander persisted up to 22 days on brinjal on field while that of C.infortunatum, E.odoratum and A.indica persisted up to 18 days. On the basis of PT indices the treatments were ranked as water extract of T.neriifolia > benzene extracts of N.oleander > C.infortunatum > E.odoratum > A.indica. The insecticidal effects of the plant extracts on D.cingulatus, H.vigintioctopunctata and S.litura were low. However, extracts of A.indica, T. neriifolia, P.odoratissimus and C.gigantea showed significant toxicity to A.craccivora. But their LC 50 values ranged from 34 to 93 per cent. Benzene extracts of C.infortunatum, A.indica, T.neriifolia and E.odoratum had high systemic action on different nymphal instars of D.cingulatus. Fourth instar nymphs were more tolerant to the insecticidal action of the extracts. The essential oils included in the experiment did not show insecticidal activity on D.cingulatus and S.litura while some caused significant mortality of A.craccivora at high doses. Sixteen out of twenty plants tested had significant juvenomimetic effect on D.cingulatus in one or more than one of the extracts tested. When the different extracts were ranked on the basis of percentage of normal adults and their sterility (an index of the possible build up of the post treatment populations of the test insect) benzene was found to be the best and it was followed by water while acetone and ether were on par and far less effective. T.neriifolia, A.indica and E.odoratum caused 100 per cent sterility of D.cingulatus in water and benzene extracts and above 90 per cent sterility in other two extracts. C.infortunatum and N.oleander caused 100 per cent sterility in acetone, benzene and water extracts. The juvenomimetic effect of S.litura was much lower than that on D.cingulatus. All the extracts of A.indica and N.oleander, water and acetone extracts of T.neriifolia and V.negundo, benzene and acetone extracts of A.vesica, acetone extract of E.odoratum, ether extract of M.esculenta and C.variegatum caused 100 per cent sterility to the insect and hence the treatment would limit the contribution from the treated insects to the next generation to zero level. Bioassay studies showed that acetone extracts of C.infortunatum had highest juvenilising effect on D.cingulatus. It was closely followed by A.indica. T.neriifolia, N. oleander and E.odoratum were much less effective than A.indica and C.infortunatum. Benzene extracts were more active than acetone extracts and were ranked as A.indica > C.infortunatum > N.oleander > E.odoratum > T.neriifolia. Considering both the extracts C.infortunatum came on par with A.indica. N.oleander and E.odoratum were also found promising. The essential oils caused morphogenetic abnormalities in the developing numphs of D.cingulatus. The dosage at which high sterility could be obtained were too high to ensure economic viability of its use in field. Lower effective dosages, cheaper and comparably effective oils may have to be found out for wide use of essential oils for pest control. Benzene extracts of A.indica, E.odoratum, C.infortunatum, T.neriifolia and N.oleander and water extracts of T.neriifolia as 2% emulsions reduced the populations of H.vigintioctopunctata, C.insolitus and A.gossypii on brinjal and H.vigintioctopunctata on bitterground significantly in the field experiments. All the treatments (except T.neriifolia againist A.gossypii) came on par with the insecticide check, carbaryl 0.2 per cent suspension, in reducing the population. The studies have thus established that the antifeedant and juvenoid effects of five plants screened out from the local flora were as promising as those of A.indica, the well recognized plant source for such activity and the extracts of these plants can be exploited effectively in the integrated control of crop pests. | |
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