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

Abstract

The poultry industry, particularly the laying hen sector, faces significant challenges from parasitic infestations. Among these, *Dermanyssus gallinae*, commonly known as the poultry red mite, stands out as the primary ectoparasite, posing a substantial threat to poultry health and productivity. The conventional approach to controlling these mites predominantly relies on the application of chemical acaricides. However, the continuous and widespread use of these synthetic chemicals has led to an alarming and increasing incidence of drug resistance in mite populations. This escalating issue underscores an urgent and critical need to identify and develop alternative, more sustainable strategies for the effective control of *D. gallinae*.

In light of this pressing demand, natural products, particularly essential oils, have emerged as promising candidates. Spices, in particular, are globally popular commodities renowned not only for their culinary attributes but also for their diverse medicinal properties. A growing body of scientific evidence has demonstrated that essential oils (EOs) derived from various spices possess potent biological activities, including insecticidal, repellent, and feeding deterrence effects against a range of pests. Building upon this knowledge, the present study embarked on a comprehensive evaluation of nine distinct spice essential oils to assess their potential as natural acaricides against *D. gallinae*. The chosen spice EOs for this investigation included star anise, garlic, cassia, clove, pepper, ginger, chili, cumin, and nutmeg. Each of these EOs was rigorously tested for four key aspects of acaricidal efficacy: contact toxicity, fumigation activity, residual toxicity, and ovicidal activity, providing a holistic assessment of their potential.

The results from the contact efficacy assays yielded highly promising outcomes. Among the tested essential oils, garlic, cassia, and clove EOs unequivocally demonstrated the most superior acaricidal effect on *D. gallinae*. At a 10% concentration, these three essential oils achieved a remarkable 100% mortality rate among mites within just 24 hours of exposure. Furthermore, star anise essential oil also exhibited significant lethal activity, causing 75.0% mortality, closely followed by ginger essential oil, which resulted in 71.9% mortality. These findings highlight the potent immediate contact action of several spice EOs.

In the fumigation assay, which assesses the efficacy of volatile compounds, star anise, garlic, cassia, clove, and pepper essential oils exhibited a significantly higher vapor efficacy compared to the other tested EOs. Within a period of 24 to 48 hours, these five essential oils achieved a complete 100.0% mite mortality, indicating their strong ability to act through the air and affect mites remotely. This suggests their potential utility in enclosed poultry house environments.

Perhaps one of the most critical aspects for practical application in pest control is residual activity. In this regard, cassia, clove, and garlic essential oils once again emerged as top performers, demonstrating the best residual toxic effects. Their acaricidal activity persisted effectively for up to 6 days post-application, maintaining mortality rates exceeding 50%. Star anise and ginger essential oils also showed notable residual effects, although for shorter durations, maintaining efficacy for 4 and 2 days, respectively. This prolonged activity is a significant advantage for field applications, reducing the frequency of treatments.

Furthermore, the study extended its investigation to the ovicidal activity of these essential oils, which is crucial for breaking the mite life cycle and preventing future infestations. Garlic, cassia, and clove essential oils demonstrated particularly effective ovicidal activity, significantly inhibiting egg hatching. The egg hatchability rates were remarkably low: 22.2% for garlic EO-treated eggs, 13.3% for cassia EO-treated eggs, and 28.9% for clove EO-treated eggs. These figures translate to an impressive egg hatching inhibition rate of more than 70%, underscoring their potential to disrupt mite reproduction.

In conclusion, this comprehensive study has unequivocally demonstrated the substantial potential of various spice essential oils as highly effective natural acaricides against *D. gallinae*. BMS-502 Given their natural origin, relatively low cost, and readiness for use, these spice EOs may be considered as valid, eco-friendly, and sustainable alternatives to the chemical acaricides currently employed in commercial poultry farms. Their multi-faceted efficacy, encompassing contact, fumigation, residual, and ovicidal properties, positions them as promising candidates for integrated pest management strategies in the poultry industry, offering a pathway towards reducing reliance on synthetic chemicals and mitigating the challenges of drug resistance.