Insecticidal factors from the seeds of Erythrina indica Lam against Hyblaea puera, the most serious defoliator pest of teak
The organic solvent extracts from the seeds of Erythrina indica were tested for their insecticidal action against Hyblaea puera, the most important defoliator pest of teak. The larvicidal activity of the petroleum ether, chloroform, methanol, ethyl alcohol, ethyl acetate, acetone and water extracts from the seeds of E. indica on the 3rd instar larvae of H. puera showed 100% mortality even with least concentration (0.25%). The ovicidal activity was exhibited by chloroform and ethyl acetate extract. Both the extracts exhibited highest egg hatch inhibition (56%) at highest concentration (2%). The least LC50 (1.15%) shows that ethyl acetate extract is better than chloroform extract (1.78). Two compounds were isolated from the ethyl acetate extract of the seeds of Erythrina indica by column chromatography. The compounds were identified using HPLC, GC MS, and NMR. Compound 1 was a mixture of linoleic acid and oleic acid. Compound 2 was a mixture of linoleic acid and oleic acid ester with a glycerol unit attached to it. Compounds 1 and 2 were biologically active and exhibited potent insecticidal activity against the 3rd instar larvae of H. puera. The result showed that Compound 2 isolated from E. indica exhibited highest mortality (72%) at concentration (0.125%). At highest concentration (0.5%) highest mortality (92%) was exhibited by Compound 2 which on comparison is on par with the Neemark (Azadirachtin) exhibiting highest mortality (100%). The study is complementary with earliar works and proves that the seeds of E. indica has immense potential to be utilized as botanical insecticide.
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Journal of Tropical Forestry and Environment,
University of Sri Jayewardenepura, Nugegoda, Sri Lanka