Bioactivities of essential oil of Eucalyptus globolus L. against Tribolium castaneum

Abstract

Background & Aim: The use of herbal extracts as safe and effective factors for eradicating of stores pests has attracted much attention. In this paper, the bio-effects of fumigation and repellent effects of essential oil of <em>Eucalyptus globolus</em> were investigated on red flour beetle. Experimental: In this study, the toxicity, fumigation and repellency contacts were assayed by topical application and impregnation of filter papers (Whatman N°1). One micro liter of different essential oil concentrations were placed on thorax of adults by micro-applicator apparatus in topical application experiments. For impregnation method, treated filter papers were attached to top or bottom of Petri plates in two different assays in order to separation of fumigant and contact toxicity. Fumigation bioassays were carried out in 40 ml glass vials. For evaluating repellency value of the essential oil, the numbers of insects present on treated compared to untreated surface of filter papers were recorded after 2h of exposure and percentage repellency (PR). The essential oil achieved LD₅₀ at 0.22 µl Insect^-1 in topical method. It needs three time more essential oil for control of 90 percent of insects (LD₉₀ = 0.69 µl/I) based on pro-bit analysis of data. Results & Discussion: We rejected the current method of contact toxicity evaluating as fumigation had more ‎contribution in filter paper treating assays. Percentage mortalities of ‎‏20.4‏‎, ‎‏14.8‏‎ and ‎‏14.8‏‎ were ‎evaluated by ‎‏1.04‏‎, ‎‏0.52‏‎ and ‎‏0.56‏‎ µl/cm‏^2‏‎ of essential oil following subtraction of fumigant ‎toxicity portion. The LC‏₅₀‏‎ of ‎‏113.6‏‎ µl/L of air were estimated in fumigation bioassays. Here ‎the equivalent LD‏_90‏‎ was only ‎‏168.9 µl/L of air. The average repellency value of the four ‎concentrations, 0.93‏‎, ‎‏0.62‏‎, ‎‏0.31‏‎ and ‎‏0.1‏‎ µl/cm‏²‏‎ were ‎‏83.2 percent that is of group V (‎‏100-80.1‏‎‎‎% repellency). Industrial and practical recommendations: The limitation and prohibition of using chemical fumigation compositions appropriate have made the need of alternative pesticides more tangible. The considerable quantity of <em>Eucalyptus</em> extract, being harmless for biologic systems and its appropriate effectiveness on store pets are the factors that make this herbal composition important to be substituted for dangerous chemical compositions.