Fumigant toxicities of essential oils and two monoterpenes against potato tuber moth (Phthorimaea operculella Zeller)

SummaryIntroduction:The potato tuber moth (PTM) is the major economic pest of potato. Different approaches were tried to prevent and control this pest including natural pesticides and synthetic fumigants.Objectives: This study was conducted to evaluate the insecticidal activity of the essential oils of thyme and myrtle. In addition to evaluating the insecticidal activity of carvacrol and eucalyptol against the different life stages of potato tuber moth using a fumigation bioassays.Methods:Thyme and myrtle oils were extracted from wildThymus syriacusBoiss. and wildMyrtus communisL. by hydrodistillation. Fumigation experiments were conducted on potato tuber moth of different stages of development (eggs, larvae, pupae, and adults), using standard methods. The potato tuber moth was treated for different periods using different concentrations of the essential oils. One-way analysis of variance (ANOVA) was applied on the mortality percentages data to estimate the significance of differences between treatments atp<0.05. Probit analysis was used to estimate the LC50, LC90and LT50.Results:Adult stage was the most sensitive to essential oils vapours with LC50value of 0.5μl/l air. Whereas, pupal stages were the most tolerant. The essential oil of thyme possessed the strongest fumigant toxicity against eggs with a LC50value of 6.1μl/l air. The two monoterpens showed varied fumigant toxicity against adult stage. Carvacrol achieved 100% mortality at 0.125μl/l air after 6 h, and 0.025μl/l air after 48h exposure with LT50period of 0.5 h.Conclusion:The present work demonstrated thatT. syriacusessential oil is a promising natural fumigant against the different developmental stages of PTM.