Acaricidal activity of clove bud oil compounds against Tyrophagus putrescentiae (Acari: Acaridae)

Abstract

The acaricidal activity of clove (Eugenia caryophyllata) bud oil compounds (acetyleugenol, β-caryophyllene, eugenol, α-humulene), and congeners of eugenol (isoeugenol, methyleugenol) against adult Tyrophagus putrescentiae was examined using impregnated fabric disc and fumigation methods, and compared with that of benzyl benzoate. Responses varied according to compound and dose. LD50 values indicated that the compound most toxic to T. putrescentiae adults was methyleugenol (1.18 μg/cm2) followed by isoeugenol (8.21 μg/cm2), benzyl benzoate (8.85 μg/cm2), β-caryophyllene (11.77 μg/cm2), eugenol (12.11 μg/cm2), and α-humulene (12.90 μg/cm2). Very low activity was observed with acetyleugenol (28.72 μg/cm2). These results indicate that hydrophobicity of the four phenylpropenes (acetyleugenol, eugenol, isoeugenol, methyleugenol) plays a crucial role in T. putrescentiae toxicity. The typical poisoning symptom of the test compounds was a similar death symptom of the forelegs extended forward together, leading to death without knockdown, whereas benzyl benzoate caused death following uncoordinated behavior. In fumigation tests with adult T. putrescentiae, all four phenylpropenes were more effective against the mites in closed containers than in open ones, indicating that the mode of delivery of these compounds was largely due to action in the vapor phase. The clove bud oil compounds as well as isoeugenol and methyleugenol merit further study as potential storage mite control agents or as lead compounds.