Toxicity of Juniperus oxycedrus oil constituents and related compounds and the efficacy of oil spray formulations to Dermatophagoides farinae (Acari: Pyroglyphidae).

Abstract

The American house dust mite (AHDM), Dermatophagoides farinae Hughes (Acari: Pyroglyphidae), is recognized as an important source of allergens in the domestic environment. This study was conducted to determine whether 19 constituents from essential oil of cade, Juniperus oxycedrus L. (Cupressaceae), eight structurally related compounds, and another 16 previously known cade oil constituents were toxic for adult AHDMs and to determine the route of acaricidal action of the test compounds, as well as to assess the control efficacy of four experimental spray formulations containing the oil (10-40mg/L sprays). In a fabric-circle contact mortality bioassay, methyleugenol (LD50, 5.82µg/cm2) and guaiacol (8.24µg/cm2) were the most toxic compounds against the mites, and the toxicity of these compounds and benzyl benzoate did not significantly differ. High toxicity was also observed with eugenol, m-cresol, and nerolidol (LD50, 12.52-19.52µg/cm2), and these compounds were significantly more toxic than N,N-diethyl-3-methylbenzamide (DEET) (LD50, 37.67µg/cm2). Cade applied as 30 or 40mg/L experimental sprays provided 96 and 100% mortality against the mites, respectively, whereas permethrin (cis:trans, 25:75) 2.5g/L spray treatment resulted in 17% mortality. In vapor-phase mortality tests, the compounds described were consistently more toxic in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapor. Reasonable mite control in indoor environments can be achieved by spray formulation containing the 40mg/L cade oil as potential contact-action fumigants.