Fumigant toxicity of three essential oils on Phthorimaea operculella (Zeller) and their impacts on parasitism of Trichogramma brassicae (Bezdenko)

In the present study, the lethal and sublethal effects of essential oils of marjoram, basil, and mint were evaluated on P. operculella. Also, the parasitism percentage of T. brassicae was assessed on the eggs of P. operculella treated with sublethal concentration (LC30) of these essential oils under laboratory conditions. The gas chromatography-mass spectroscopy analysis indicated that carvacrol (26.02%), estragole (62.27%), and carvotanacetone (57.47%) were the major constituents of the studied essential oils, respectively. Based on the LC50 values of marjoram, basil, and mint essential oils (3.59, 2.53, and 2.37 µl/liter air, respectively), the mint essential oil had the highest fumigant toxicity on the eggs of P. operculella compared to other essential oils. The LC30 values of essential oils (2.61, 1.20, and 1.81 µl/liter air, respectively) were used to evaluate the sublethal effects. The sublethal concentrations of essential oils significantly affected the parameters of P. operculella. The shortest and longest total pre-oviposition period (TPOP) were observed on control (19.60 days) and O. basilicum essential oil (22.19 days). The values estimated for intrinsic rate of increase (r) in the control and marjoram, basil, and mint essential oils were 0.19, 0.11, 0.12, 0.10 day, respectively. Also, the parasitism rate of T. brassicae was recorded on control (81.11%) followed by basil essential oil (64.44%). These results suggested simultaneous usage of essential oils and parasitic wasps as a reliable option for sustainable managementofpotato tuber worm in the storage facilities.