Acaricidal Activity of Tabebuia impetiginosa Bark-Derived Constituent against Domestic and Spider Mites (Arachnida: Acari)

The acaricidal activity of a major constituent derived from the methanol extract of Tabebuia impetiginosa bark was compared with those of benzyl benzoate and abamectin using various bioassays against Dermatophagoides spp., Tetranychus urticae and Tyrophagus putrescentiae. The chloroform fraction obtained from the methanol extract of T. impetiginosa bark produced strong and weak acaricidal activities against T. urticae, Dermatophagoides spp., and T. putrescentiae. The active constituent of T. impetiginosa bark was identified as 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone by spectroscopic analyses. The $LC_{50}$ (lethal concentration 50) values of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone and abamectin against T. urticae were 0.015 and 0.312 mg/L, respectively. Based on $LC_{50}$ values, 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone was about 20.8 times more toxic than abamectin against T. urticae. However, benzyl benzoate showed higher acaricidal activity than 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone against Dermatophagoides spp. and T. putrescentiae. These results indicate that 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone has potential for the development of new preventive agents for the control of T. urticae.