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Abstract

The adverse effects of synthetic acaricides on humans, animals, non-target organisms and the ecosystem are serious problems. Thus, there is a new trend to use nanotechnology for developing new, natural, bio and safe acaricides for mite control in green-pest management. This is the first work for preparing a nanoformulation of rosemary essential oil (EO) and evaluating its effect against the two-spotted spider mite Tetranychus urticae Koch. GC/MS analysis of rosemary EO showed that 1,8 cineole (31.45%), borneol (11.07%), α-pinene (10.91%), D-limonene (9.19%), L-linalool (8.86%), D-camphor (7.32%), γ-terpinene (3.92%), linalyl acetate (3.37%), α-terpineol (3.32%), and p-cymene (1.82%) were the major components. After 6 min of sonication, a nanoemulsion of rosemary EO was formulated with a droplet size of 139.9 nm. The balance between oil (lyophilic) and surfactant (hydrophilic) was correlated with the droplet size and the stability of the nanoemulsion. Spray application of rosemary nanoemulsion showed high acaricidal activity against immature and adult two-spotted spider mites T. urticae with LC50 723.71 and 865.68 μg · ml−1 and the toxicity increased by 54.15 and 52.69% for immature and adult mites, respectively. There were no toxic effects or mortality of rats treated with rosemary nanoemulsion. High acaricidal activity, stability, and safety of rosemary nanoemulsion make this nanoformulation a possible green and nano-acaricidal product. Further studies under field conditions are necessary to study the acaricidal efficiency of rosemary nanoemulsion against two-spotted spider mites and the toxic effect on predacious mites.

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Authors and Affiliations

Abdel-Tawab H. Mossa
Sahar I. Afia
Samia M.M. Mohafrash
Badawi A. Abou-Awad
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Abstract

This study investigates the acaricidal, ovicidal, and repellent effects of the Tagetes patula Linn. (Asteraceae) leaf extract against both the adult female and egg stages of Tetranychus urticae Koch (Trombidiformes: Tetranychidae) under laboratory conditions. The Tagetes patula ethanolic leaf extract [TpEtOH70%] was screened for adulticide and ovicide bioassays in order to consider its acute toxicity. One sublethal concentration was used to assess egg-laying capacity (fecundity), repellent, and oviposition deterrent activities. The chemical characterization was conducted by gas chromatography-mass spectrometry (GC-MS) analysis to identify the TpEtOH70% bioactive components. Results showed that the LC50 value of TpEtOH70% leaf extract predicted by Probit analysis against T. urticae adult females at 24 h was 0.99%. The TpEtOH70% leaf extract showed a significant toxic effect as the highest mean mortality rates (± SE) of the treated adult females was 88.9 ± 3.7%. However, the TpEtOH70% leaf extract was insignificant in affecting the egg-laying capacity of the adult females treated with a sublethal dose of 0.5% even after 72 h. The TpEtOH70% leaf extract was classified repellent since the repellent index (RI) value was lower than 1 – SD. In addition, it had a high oviposition deterring effect based on a 100% reduction of the total number of eggs. The TpEtOH70% leaf extract had a significant ovicidal effect on T. urticae eggs, with 56.04% reduction in hatching. Five bioactive compounds from various classes of phytochemicals were identified in the TpEtOH70% leaf extract and the major compound was phytol (62.72%). This pioneering investigation reveals the adulticidal, ovicidal, and repellent activities of the TpEtOH70% leaf extract against T. urticae. A combination of multiple modes of action of different plant components may act alone or in synergism to delay the development of mite resistance.

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Authors and Affiliations

Manal Sayed Mohamed Ismail
Hend Maroof Tag
Marguerite Adly Rizk

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