Enhanced repellency of binary mixtures of Zanthoxylum piperitum pericarp steam distillate or Zanthoxylum armatum seed oil constituents and Calophyllum inophyllum nut oil and their aerosols to Stomoxys calcitrans

BACKGROUND: The repellency to stable fly, Stomoxys calcitrans (L.), of Zanthoxylum piperitum (L.) DC pericarp steam distillate (ZP-SD), Zanthoxylum armatum DC seed oil (ZA-SO) and their constituents alone or in combination with Calophyllum inophyllum L. nut oil (CI-NO), as well as six aerosol formulations containing ZP-SD or ZP-SO and CI-NO, was compared with that of a synthetic repellent, DEET, using an exposed human hand bioassay. RESULTS: At 0.20 mg cm(-2), ZP-SD treatments resulted in 91 and 68% repellency following 30 and 60 min exposure respectively, while DEET gave 100 and 84% repellency. ZA-SO was less effective than ZP-SD. At 0.2 mg cm(-2), the most active constituents, cuminaldehyde, cuminyl alcohol, limonene and methyl cinnamate, gave 82, 74, 74 and 64% repellency at 30 min respectively, but DEET gave 100 and 87% repellency at 30 and 60 min. An increase in effectiveness and duration of repellency was produced by binary mixtures of ZP-SD, ZA-SO or bioactive constituents (each 0.01 mg cm(-2)) and CI-NO (0.99 mg cm(-2)). The repellency of aerosols containing 2.5% ZP-SD or 2.5% ZA-SO and 2.5% CI-NO was comparable with that of 5% DEET aerosol. CONCLUSION: Mixtures formulated from ZP-SD, ZA-SO or bioactive constituents and CI-NO could be useful as potential repellents for the control of stable fly populations in light of global efforts to reduce the level of highly toxic synthetic repellents. (C) 2010 Society of Chemical Industry