Screening of essential oils with acaricidal activity against the poultry red mite (Dermanyssus gallinae) and analysis of active components.

Dermanyssus gallinae is a common ectoparasite in the laying hen industry, damaging chicken health by sucking blood. With mites developing acaricide resistance, there's an urgent need for alternatives. In this study, we evaluated the efficacy of 34 essential oils (EOs) on D. gallinae through contact and fumigation toxicity tests. Results from contact efficacy studies showed that clove basil, cinnamon, thyme, wintergreen, oregano, palmarosa, lemongrass and geranium EOs possessed significant acaricidal activity with LC values ranging from 0.3 to 1.0 mg/cm, among which cinnamon was the most toxic. In the fumigation assay, oregano, lemongrass, palmarosa, clove basil, thyme and cinnamon both in the closed and open systems had a significantly higher vapour efficacy than others after 72 h (P < 0.01), with mite mortality of 100.0 %. Cinnamon possessed the highest residual toxicity, with its effectiveness lasting up to 3 days. Clove basil, cinnamon, geranium, palmarosa, oregano and thyme exhibited effective ovicidal activity, with egg hatchability of 1.7 ± 2.9, 13.3 ± 7.6, 15.0 ± 13.2, 0.0 ± 0.0, 16.67 ± 10.4, and 18.33 ± 2.9 %, respectively. Among them, palmarosa achieved the most significant ovicidal activity. GC-MS analysis of the major compounds in the eight EOs found eugenol (77.9 %) was dominant in clove basil; trans-cinnamaldehyde (80.1 %) in cinnamon; cephrol (20.9 %) and citronellyl formate (11.4 %) in geranium; geranaldehydeial (39.7 %) and neral (36.9 %) in lemongrass; carvacrol (55.8 %) in oregano; thymol (30.3 %) in thyme; geraniol (41.0 %) and neryl alcohol (28.3 %) in palmarosa; and methyl salicylate (99.4 %) in wintergreen. These results suggest that the eight most toxic EOs may serve as effective and environmentally friendly alternatives to conventional acaricides.