Adjuvants for Traps Baited with Carbon Dioxide: What is Their Mode of Action?

PRINCIPAL INVESTIGATOR : Ring T. Cardé Department of Entomology, UC Riverside

SUMMARY: The use of adjuvants such as octenol to increase catch of mosquitoes traps baited with carbon dioxide has the potential to increase trap sensitivity and species selectivity. Although many field tests of such adjuvants have been conducted, how they work remains speculative. We propose two hypotheses: they act with carbon dioxide at long range to lower the odor threshold (and thereby increase the odor plume’s effective reach) or they act near the trap to increase the time of local search (which increases the likelihood of a mosquito traversing the trap’s “suction zone”). Because of several technical barriers to testing these hypotheses in the field, we propose wind-tunnel tests aimed at establishing if one (or both) explanations are correct. As exemplars, we will use Culex quinquefasciatus with nonanal and Aedes aegypti with octenol and two kairomone mixtures. Understanding how adjuvants work may lead to new behavioral methods that enable screening for new adjuvants and it may provide a bioassay for testing for natural constituents of host odors. At present we do not lack for candidate compounds—for example, hundreds are known from human skin “head space.” Which blend of compounds are actually used, however, generally remains a mystery.

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