Acaricide Flupentiofenox Inhibits the Mitochondrial β-Oxidation Pathway of Fatty Acids

A newly developed pesticide, flupentiofenox, has a unique trifluoroethyl phenylsulfoxide structure, and it powerfully affects spider mites, including those with resistance to multiple commercial acaricides. To clarify the mode of action of flupentiofenox, we investigated its effect on mitochondrial energy generation. We observed that flupentiofenox decreased adenosine triphosphate (ATP) levels in two-spotted spider mites (Tetranychus urticae) at a practical dose. Flupentiofenox potently inhibited mitochondrial oxygen consumption under conditions of palmitoyl-carnitine or octanoic acid supply, but not under conditions of pyruvate supply. These results show that flupentiofenox inhibits the mitochondrial fatty acid metabolic pathway between the uptake of long-chain acylcarnitine or medium-chain fatty acid and the synthesis of acetyl-CoA by β-oxidation, resulting in suppressed mitochondrial energy generation. Our investigations have led us to conclude that flupentiofenox is a pesticide with a novel mode of action.