Field and laboratory evaluations of potential oviposition attractants for Aedes albopictus (Diptera: Culicidae)

We tested five volatile synthetic chemicals (dimethyl disulfide, indole, 4-methylphenol, 3-methylindole, and trimethylamine) as potential oviposition attractants of Aedes albopictus in field and laboratory experiments. The 5 synthetic compounds were loaded into controlled-release packets, which consisted of a cellulose material sealed within a permeable plastic membrane, that were used to bait water-filled ovitraps at 5 field sites. Aedes albopictus exhibited no oviposition preference for any of the baited traps versus adjacent traps containing only water. In addition, there was no difference in the mean number of eggs laid per trap-day by Ae. albopictus among ovitraps treated with the five compounds. We conducted behavioral bioassays to determine if the lack of response to the putative oviposition chemicals in the field was due to a concentration effect. A binary sticky-screen bioassay was used to measure attraction of gravid females to olfactory stimuli. Compounds were evaluated over a range of concentrations that spanned 3-5 logs (0.0083 to 8.3 or 83 mg/liter). Three concentrations of 4-methylphenol (0.083 mg/liter, 0.83 mg/liter, and 8.3 mg/liter) and 1 concentration of 3-methylindole (8.3 mg/liter) were significantly repellent. All other concentrations of the 5 chemicals tested did not attract more females than did a water control. Electoantennography indicated that Ae. albopictus did not exhibit a physiological response to 0.25 ng of any of the five chemicals tested. Because Ae. albopictus did not exhibit attraction, greater oviposition. or an electrophysiological response to any of the compounds tested, these compounds do not appear to be effective lures for baiting ovitraps for surveillance or control of this mosquito.