Mite control effect of branched chain fatty acid on the house dust mite Dermatophagoides pteronyssinus.

House dust mites, Dermatophagoides pteronyssinus are present in the indoor environments, such as pillows and carpets. In this study, we investigated the mite control effect of branched chain fatty acids (2-ethylhexanoic acid (iso-C8), 2-butyloctanoic acid (iso-C12), isopalmitic acid (iso-C16) and their mechanism of action. These fatty acids showed a higher acaricidal activity than the straight chain fatty acids. Among these, iso-C12 had the highest acaricidal activity (LC₅₀: 13mM) and more than 50% repellence rate at 0.20% (8.0mM) concentration. In the fumigant mortality bioassay, iso-C8 was 4 times more toxic than iso-C12 and isoC-16 in the gas phase. However, all branched chain fatty acids showed higher acaricidal activities on direct contact than fumigation. As the concentration of these fatty acids decreased, the number of deaths decreased and the number of escapes increased. There was no significant change in the mite epidermis due to contact with any of the fatty acids used. All branched chain fatty acids immobilized more than half of the mites within 90min of exposure. These results were consistent with the tendency of immobilizer type miticides targeting the respiratory system.