A synergist used to enhance the activity of insecticides; inhibits cytochrome P450 enzyme activity; increases the toxicity of deltamethrin to field-collected, deltamethrin-resistant strains of the bed bug C. lectularius by 40- to 176-fold at 50 μg/μL; increases the toxicity of Plictran to fourth instar larvae of susceptible strains of the cotton leafworm S. littoralis (LD50s = 0.78 and 40 μg/larva with and without piperonyl butoxide, respectively), as well as field strains (LD50s = 0.015 and 1.1 μg/larva with and without piperonyl butoxide, respectively); not toxic to the freshwater invertebrates H. azteca, C. tentans, and L. variegatus (LC50s = 530, 2,740, and 3,540 μg/L, respectively); reduces the toxicity of diazinon, chlorpyrifos, and azinphos-methyl in these organisms