| Abstrakt: |
AbstractEssential oils (EOs) obtained from plants have the potential to be environment-friendly alternatives to synthetic insecticides in agriculture. Tribolium castaneum(Herbst) is a cosmopolitan pest that causes the loss of a major proportion of stored crops. Therefore, we studied the insecticidal and repellent effects of EOs derived from the plants viz. Eucalyptus rudis, Eucalyptus crebra, and Melaleuca genistifoliaagainst larvae and adults of T. castaneum. Essential oils were derived from the leaves of each plant using hydro-distillation. Gas chromatography-mass spectrometry (GC-MS) of the extracted EOs revealed that eucalyptol, viridiflorol, α-terpineol, and eugenol methyl comprised the major components of the EOs. However, the composition and quantity of the compounds varied across EOs. Specifically, EOs derived from E. rudisexhibited the highest fumigation toxicity against adult and larval T. castaneum, followed by M. genistifoliaand E. crebra.In the presence of wheat grains, fumigation toxicity against T. castaneumdeclined by nearly threefold. Contact toxicity assays revealed that EOs from E. rudiswere overall the most effective against the pest (LC50: 0.392 μL/cm2for adult; LC50: 0.471 μL/cm2for larva) followed by M. genistifolia(LC50: 0.424 μL/cm2for adult; LC50: 0.478 μL/cm2for larva) and E. crebra(LC50: 0.471 μL/cm2for adult; LC50: 0.515 μL/cm2for larva). The LC50value of each EO was up to five times lower in adults than in larvae. Melaleuca genistifoliawas the most effective repellent against T. castaneumadults; however, its effectiveness decreased with increasing exposure time. In conclusion, the EOs of E. rudis, E. crebra, and M. genistifoliawere all viable green biopesticide alternatives to synthetic insecticides. |
