Acaricidal activity of fennel seed oils and their main components against Tyrophagus putrescentiae, a stored-food mite

The acaricidal activities of components derived from Foeniculum vulgare (fennel) seed oils against Tyrophagus putrescentiae adults were examined using direct contact application and compared with those of the compounds benzyl benzoate, dibutyl phthalate and N,N-diethyl-m-toluamide. The biologically active constituent of the F. vulgare seeds was characterized as (+)-carvone by spectroscopic analyses. On the basis of LD₅₀ values, the compound most toxic to T. putrescentiae was naphthalene (4.28 μg/cm²) followed by dihydrocarvone (4.32 μg/cm²), (+)-carvone (4.62 μg/cm²), (−)-carvone (5.23 μg/cm²), eugenol (10.62 μg/cm²), benzyl benzoate (11.24 μg/cm²), thymol (11.42 μg/cm²), dibutyl phthalate (13.11 μg/cm²), N,N-diethyl-m-toluamide (13.53 μg/cm²), methyl eugenol (39.52 μg/cm²), myrcene (39.88 μg/cm²) and acetyleugenol (72.24 μg/cm²). These results indicate that acaricidal activity of the F. vulgare seed oil could be caused by carvone and naphthalene of which the former is likely to be more important because it is 74.7 times more abundant than naphthalene. Carvone and naphthalene merit further study as potential stored-food mite control agents or as lead compounds.