Selective control of the bulb mite Rhizoglyphus robini using essential oils: Toxicity, enzyme inhibition, and predator safety

The bulb mite, Rhizoglyphus robini, is a significant pest of crops like saffron, leading to economic losses. This study evaluated the fumigant toxicity of 26 essential oils (EOs) against R. robini as a potential pest management strategy and examined their impact on the beneficial predatory mite Gaeolaelaps aculeifer. Adult females of R. robini were exposed to EO-impregnated filter papers at a concentration of 7.64 mg/L for 48 hours. Thirteen oils caused over 40% mortality, with four oils showing high toxicity (LC50 < 100 mg/L). Foeniculum vulgare was the most toxic, followed by Mentha pulegium, Anethum graveolens, and Heracleum persicum, with significant toxicity also noted in R. robini larvae. The impact on G. aculeifer was minimal, indicating these oils can selectively control R. robini without harming beneficial predators. Enzyme inhibition assays showed that F. vulgare strongly disrupted detoxification enzymes in R. robini, particularly cytochrome P450s in larvae. Optimized concentrations of these EOs, especially F. vulgare, could effectively manage R. robini while minimizing effects on predatory mites.