Resistance to conventional synthetic pesticides has been widely reported in Dermanyssus gallinae in poultry production systems. Introducing novel acaricides to poultry industry today is more urgent than ever. Research in this field recently focused on plants and plant-derived compounds as acaricides. In the present study, acaricidal activity of three plant bioactive components, carvacrol, thymol, and farnesol, was assessed against D. gallinae and compared with synthetic pesticide permethrin. Mode of acaricidal action was determined by contact toxicity and fumigant toxicity bioassays. Except farnesol which did not cause any mortality, carvacrol and thymol were found to be toxic to D. gallinae with LD50 values of 1 and 3.15 μg/cm(3), respectively. Permethrin gave the LD50 value of 31.95 μg/cm(3) which was less efficient than carvacrol and thymol. In fumigant toxicity bioassay, mortality rate in carvacrol- and thymol-treated groups in closed method was significantly higher than the open one. On the other hand, permethrin exhibited poor fumigant toxicity as there was no statistically significant difference between mortality rate in open and closed methods. These findings revealed that mechanism of acaricidal activity of carvacrol and thymol but not permethrin was mainly due to fumigant action. Results of the present study suggested that carvacrol and thymol, especially carvacrol, can be developed as a novel potent bioacaricide against D. gallinae.

Resistance to conventional synthetic pesticides has been widely reported in Dermanyssus gallinae in different aviary systems. Cardboard traps containing acaricides had been introduced as a successive device for collection and control of the poultry red mite. The present study assessed field efficacy of traps containing carvacrol in the control and reduction of D. gallinae in laying poultry farm. Two different carvacrol-based formulations were tested for their toxicity and possible repellent activity on D. gallinae to determine the most appropriate formulation and concentration to be used in the field study. In vitro tests confirmed that 1 % carvacrol formulation with ethoxylated castor oil as emulsifier was significantly toxic to D. gallinae without any dissuading effect in comparison to ethanol and higher concentrations of carvacrol (p < 0.05). A subsequent in vivo experiment in a cage system laying farm demonstrated significant acaricidal activity for traps containing 1 % carvacrol. Throughout the study, untreated cardboard traps were used for monitoring mite populations. Carvacrol-impregnated traps were efficacious in the control of D. gallinae and led to over 92 % reduction in mite's population after 2 week of application. Toxic effects of carvacrol maintained through 2 weeks after the last application of traps. Results of the present study suggested that effective control of the poultry red mite can be achieved by traps containing carvacrol. These traps can be used safely in poultry facilities without any concern about residues in eggs, meat, and environment.