Investigation of biochemical and enzymatic changes induced by emulsion and ‎nanoemulsion formulations of some essential oils and an herbal extract on Bemisia ‎tabaci (Gennadius)‎

Some essential oils and plant extracts have shown suitable insecticidal properties against the sweetpotato whitefly, Bemisia tabaci. In this study, essential oils of rosemary, peppermint and eucalyptus and extract of thyme were formulated separately in Tween 80 as well as formulated in the form of nanoemulsion and bioassyed against 2nd instar nymphs of B. tabaci. The bioassay tests were done by leaf dip method on the leaves containing 2nd instar nymphs and LC50swere determined. The LC50 of rosemary, peppermint, eucalyptus essential oils and thyme extractprepared in Tween 80 were estimated as 4198, 3925, 4312 and 9626 mL/L and LC50 of nanoemulsion of above itemswere estimated as 2759, 2987, 3189 and 5659 mL/L, respectively. The results showed that nanoemulsion of rosemary and peppermint essential oils have the highest toxicity on the 2nd instar nymphs of B. tabaci. Also, effects of combination of essential oils and extract formulation on biochemical and enzymatic changeswere investigated with LC50 of T1 (emulsified from essential oils and the extract), T2 (extract emulsion) and T3 (emulsification of essential oils). The amount of activities of esterases and glutathione s-transferases were increased in T1, T2 and T3 treatments; while, the cholinesterase activity was not affected. The amount of energy reserves (total lipid, carbohydrate and protein) decreased significantly in T1 and T3 treatments; although the amount of total glycogen was not affected significantly by treatments. Therefore, T1 and T3 treatments showed a greater effect on the biochemical parameters, by induction of detoxification of some enzymes and reducing some of the energy reserves, in 2nd instar nymphs of sweet potato whitefly.