Effects of extracts of Clerodendron infortunatum on the epilachna beetle Henosepilachna Vigintioctopunctata F with relation to safety of its natural enemies
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Date
1995
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Department of Agricultural Entomology, College of Agriculture, Vellayani.
Abstract
Flower, leaf, root and stem extracts of clerodendron infortunatum were screened for their antifeedant activity against grubs of Henospilachna vigintictopunctata using water, acetone, benzene, ethnol and petroleum other as extractants.
Based on mean leaf protection and larval starvation of different plant parts, leaf and flower portions were found to be more effective than root and stem. Among the solvents, acetone and benzene gave higher leaf protection. High larval starvation was caused by acetone followed by water, benzene, ethanol and petroleum ether.
Fresh plant parts were found to be more effective than shade and sun dried material. Shade and sun dried leaves and flowers showed high activity in water extract. The least reduction in antifeedant activity under shade and sun drying was observed in leaf.
Different parts of C.infortunatum did not cause significant insecticidal action against H.vigintioctopunctata.
Regarding growth inhibitory activity, flower and leaf were found to be more effective when they were used as fresh materials. Shade, and sun dried leaves were found significantly superior to all other plant parts in producing less number of normal adults. When the different part of C. infortunatum were ranked on the bases of the percentage of normal adult emergence, acetone and benzene topped. The least reduction in hormonal activity of the extracts of different plant parts dried under shade and in sun was observed in the case of stem, followed by root, leaf and flower. Water was found to be the most effective solvent for extracting dried plant parts.
The sterility percentages observed in different treatments were found to be very low. In the bioassay of the C.infortunatum extracts using freshly laid eggs of H.vigintioctopunctata, it was observed that the hatchability of eggs was reduced significantly by different treatments, compared to control.
The mortality observed on the parasite C. johnsoni when treated with water and acetone extracts of leaf and flower was very low. Water extracts were safer than acetone extracts of leaf and flower. The treatments did not affect the extent of parasitization and the progeny emerging from the parasitized treated grubs.
In the field experiment, acetone and water extracts of leaf mixed with teepol reduced the population of H. vigintioctopunctata on bittergourd significantly. These treatments were on par with the insecticide check carbaryl 0.15 per cent. The clerodendron extracts did not affect the predator population in the treated plots, whereas it was totally absent in carbary1-treated plot.
The results of the present investigation clearly indicate the safety of clerodendron extracts to the non-target organisms and the possibility of utilizing crude extracts of C.infortunatum as a potential pesticide for ecologically and economically sound insect pest management.
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Citation
170727