In vitro acaricidal activity of spice essential oils against the poultry red mite (Dermanyssus gallinae)

Dermanyssus gallinae is the primary ectoparasite associated with laying poultry, and is usually controlled with chemical acaricides, which lead to the development of drug resistance. Thus, there is an urgent need to identify alternative strategies for controlling D. gallinae. Spices are popular commodities with highly edible and medicinal values, and spice essential oils (EOs) have been demonstrated to function as insecticides, repellents, or feeding deterrence. In this present study, nine spice EOs (star anise, garlic, cassia, clove, pepper, ginger, chili, cumin and nutmeg) were evaluated for their contact, fumigation, residual and ovicidal toxicity against D. gallinae. Contact efficacy results demonstrated that garlic, cassia and clove EOs exhibited the best acaricidal effect on D. gallinae, with 100 % mortality after 24 h at 10 % concentration, also star anise (75.0 %) and ginger (71.9 %) exhibited high lethal activity. In the fumigation assay, star anise, garlic, cassia, clove and pepper EOs had a significantly higher vapour efficacy than others after 24-48 h (P < 0.05), with mite mortality of 100.0 %. Notably, cassia, clove, and garlic EOs had the best residual toxic effects, lasting up to 6 d with mortality rates of more than 50 %, followed by star anise and ginger, which could be maintained for 4 and 2 d, respectively. Furthermore, garlic, cassia and clove exhibited effective ovicidal activity, with egg hatchability of 22.2 %, 13.3 %, and 28.9 %, respectively, indicating that the egg hatching inhibition reached more than 70 %. This study has demonstrated the potential of spice EOs as natural acaricides against D. gallinae, which may be considered cheap and ready-to-use products as valid, eco-friendly alternatives to acaricides currently used in poultry farm.