Toxicological effects of Melaleuca ericifolia and Taxodium distichum extracts on adults rust-red flour beetle

Abstract

Petroleum ether and acetone extracts of leaves from swamp paper bark (Melaleuca ericifolia) and bald cypress (Taxodium distichum) were tested for their contact and stomach poison activity on adults Tribolium castaneum Herbst (Coleoptera: Tenebrionidae). The results showed that, percentage of mortality increased with increasing the concentration of different extracts and exposure time. Extracts of Swamp paper bark gave higher mortality percent compared with that from bald cypress. Petroleum ether extract of swamp paper bark was found to be the most potent on T. castaneum adults with LC25 , LC50 and LC95 values (1.65%, 2.59% and 7.79% (w/w), respectively) at 48 hours exposure period. The bio-residual activity of LC95 of petroleum ether extract of swamp paper bark continued up to 13th weeks in treated adults of Tribolium castaneum. On the other hand, treatment with LC25 and LC50 significantly reduced the number of deposited eggs with complete reduction (100% ) in their hatchability and progeny. Treatment of T. castaneum adults with LC50 of petroleum ether extract of swamp paper bark caused significant increase in both carbohydrates and proteins content compared with control, while significant decrease in lipids content was noticed. Petroleum ether extract of swamp paper bark at LC95 values, caused adverse effects on wheat grains germination at initial time and after storage period but water absorption was not affected. Phytochemical screening of petroleum ether extract of swamp paper bark revealed that methyl eugenol was the major component. The presence of some of these compounds may be responsible for the insecticidal action of the extract of this plant. Based on the results of this study, petroleum ether extract of swamp paper bark could serve as an alternative to synthetic insecticides for the protection of stored wheat from rust-red flour beetle.