Repellent and lethal effect of essential oils of rosemary, peppermint and eucalyptus and thyme extract, formulated as nano- and microemulsions, on Bemisia tabaci (Homoptera:Aleyrodidae) under greenhouse condition

Some essential oils and plant extracts potentially possess insecticidial properties against Sweetpotato whitefly, Bemisia tabaci Gen.; however, the practical and commercial use of these compounds have not developed due to their volatility and instability . In this study, essential oils of Rosmarinus officinalis L., Mentha piperita L. and Eucalyptus globules L. and extract of Thymus vulgaris L., were formulated as micro and nano-emulsion, and their insecticide efficiency and oviposition inhibitory effects were tested under greenhouse conditions. First, bioassey tests were done using the leaf dipping method, on 2nd and 3rd nymphal instar and LC90 was estimated. Then, the oviposition inhibitory test with choice test method (by measuring the index of laying on plants), as well as eggs mortality rate, and all nymphal and pupa mortality rate at a concentration of LC90 were calculated, in comparison with herbal soap Palizin® distilled water and control (without any treatments). Nano-emulsion treatment containing all essential oils (2% of each ) at a concentration of LC90, had a high toxicity of 3.1208 mg/l on 2nd and 3rd nymphal instar in comparison with other treatments . Also, this treatment with an average of 18.2% had the lowest egg percentage per treated plant, indicating the highest oviposition inhibitory activity. Moreover, this treatment showed an average egg mortality of 25.0%, while, in nymphal and pupal satge, average mortality of 51.6% was recored. Micro-emulsion treatment containing essential oils and extracts (2% of each essential oils and 20% of extract) also exhibited acceptable effects (the above parameters were 3.4617 mg/l, 23.3%, 42.3% and 74.0% respectively). The efficacy of these two treatments was higher than herbal soap Palazin® and other treatments, thus these two treatments can be used in the Integrated Pest Management, after doing the complementary tests.