Attraction of Culex pipiens (Diptera: Culicidae) to flower volatiles

Methylene chloride extracts of flowers from 4 plants (common milkweed, Asclepias syriaca L.; ox-eye daisy, Leucanthemum vulgare Lamarck; Canada goldenrod, Solidago canadensis L.; and yarrow, Achillea millefolium L.) were tested in a dual-port olfactometer for attractiveness to female northern house mosquitoes, Culex pipiens pipiens L. Fifty milligrams of extract was used for each test, which was equivalent to the amount of extract from flowers of 0.58 common milkweed inflorescences, 1.75 ox-eye daisy flower heads, 0.33 Canada goldenrod plants, or 3.14 yarrow plants. Significantly more Cx. pipiens responded to the common milkweed flower extract than to a control. Ox-eye daisy, Canada goldenrod and yarrow flower extracts were not significantly attractive to this species. A headspace sample of the common milkweed extract was collected by solid phase micro-extraction and analyzed by gas chromatography-mass spectrometry. The most abundant compounds in the headspace sample were 2-phenylethanol and benzyl alcohol. Analysis of the common milkweed extract and standards of 2-phenylethanol and benzyl alcohol by gas chromatography-flame ionization detection confirmed that these compounds were present in the extract. Cx. pipiens did not respond to synthetic blends of these 2 compounds when tested in a dual-port olfactometer.