Comparative acaricidal and sublethal effects of diatomaceous earth and Ocimum basilicum essential oil against the citrus brown mite, Eutetranychus orientalis (Klein), under laboratory and semi-field conditions

<title>Abstract</title> <p> <bold>Background</bold> <italic>Eutetranychus orientalis (Klein) (Acari: Tetranychidae), the citrus brown mite is an important economic phytophagous pest of citrus and several vegetable and field crops. The search for environmentally safe alternatives to synthetic acaricides has increased the interest in natural products for sustainable mite management. This study evaluated the acaricidal efficacy of diatomaceous earth (DE) and Ocimum basilicum essential oil on immature and adult stages of E. orientalis under laboratory and semi-field conditions, and assessed the effects of these treatments on female fecundity.</italic> <bold>Results</bold> Both materials showed considerable concentration and time dependent acaricidal activity. Immature mites were consistently more susceptible than adults. Diatomaceous earth was more toxic than essential oil of <italic>O. basilicum</italic> with LC ₅₀ values of 20.30 and 36.52 g m ^-2 for immature and adult mites respectively compared to 0.416 and 0.504 mL L ^-1 for basil essential oil after 7 days of exposure. The DE and basil oil treatments significantly reduced female fecundity at LC₅₀ from 33.1 eggs female⁻¹ in the control to 8.3 and 17.0 eggs female⁻¹ respectively, with oviposition deterrence indices of 59.90% and 32.13%. The maximum ratio of DE (3.0 g/l) resulted in reduction of populations of immature and adult mites by 65.69% and 61.35% respectively in semi-field conditions, whereas basil essential oil resulted in reduction of populations of immature and adult mites by 66.69% and 60.88% respectively after 7 days. <bold>Conclusions</bold> Diatomaceous earth (DE) and <italic>Ocimum basilicum</italic> (basil) essential oil are recognized as highly effective and environmentally friendly acaricides. DE works by physically damaging the mite's waxy cuticle, whereas basil oil interferes with neurotransmission against <italic>E. orientalis</italic> . Diatomaceous earth showed better laboratory toxicity and more effective suppression of reproduction. The two materials showed similar reductions of mite populations under semi-field conditions. These results support their application in sustainable integrated pest management (IPM) programs as promising alternatives to conventional synthetic acaricides. </p>