Essential Oil of Eucalyptus polybractea (L.): Chemical Composition, Antifungal, Insect Repellent and Insecticidal Activities

Abstract

Eucalyptus essential oil has a wide range of bioactivity, but research on the activity of Eucalyptus polybractea is limited.  Due to the great need for sustainable pesticides, this study was carried out to assess the antifungal and insecticidal  activities of essential oil (EO) of E. polybractea. EO was extracted from the leaves by hydrodistillation and the composition  of the essential oil was determined by gas chromatography-mass spectrometry (GC-MS). The antifungal  activity was tested against the following organisms; Aspergilus niger, Fusarium graminearum, Penicillium sp1, Penicillium  expansum, Cladosporium herbarum, Penicillium sp2, Fusarium sp, Aspergilus flavus, Alternaria alternata and Trichoderma  viride which were isolated from wheat grain. The insecticidal and repellant activity was tested against stored product  pests; Tribolium castaneum. GC-MS analysis revealed a significant number of monoterpenes in the essential oil with   Eucalyptol (34.87%) being the major component. The highest antifungal activity was observed against Fusarium  graminearum, Penicillium sp2, Aspergilus flavus and Trichoderma viride. EO showed repellent activity to T. castaneum (PR =  65%, after 45 min) and highly toxic with 100% mortality after 72 hours of exposure. The study therefore revealed  significant intra-specific changes in EO quality, which is reflected in the different rates of antifungal and insecticidal   activity.