Floral volatiles with colour cues from two cucurbitaceous plants causing attraction of Aulacophora foveicollis

Aulacophora foveicollis Lucas (Coleoptera: Chrysomelidae) is an important phytophagous pest of two cucurbitaceous plants, Momordica cochinchinensis Spreng and Solena amplexicaulis (Lam.) Gandhi. The volatile organic compound profiles from flowers ofM. cochinchinensis and S. amplexicaulis were identified and quantified by gas chromatography-mass spectrometry (GC-MS) and GC-flame ionization detector (FID) analyses. Twenty nine and 28 compounds were identified in volatiles of M. cochinchinensis and S. amplexicaulis flowers, respectively. Methyl jasmonate and 3-octanol were the predominant volatiles of M. cochinchinensis flowers, whereas 1-octadecanol and 1-hexanol were most found in the headspace of S. amplexicaulis flowers. Aulacophora foveicollis were more attracted by the flower volatiles ofM. cochinchinensis than by those of S. amplexicaulis in a glass Y-tube olfactometer. A mixture of 1-heptanol, linalool oxide, 1-octanol, and nonanal in the proportions present in the headspace of both flower types elicited attraction in the insect. From 25 cm distance, A. foveicollis displayed a preference for artificial flowers of 6.5 cm diameter of S. amplexicaulis flower colour (white) over M. cochinchinensis flower colour (white-yellow). Finally, a synthetic blend (0.43 mu g 1-heptanol + 1.44 mu g linalool oxide + 0.14 mu g 1-octanol + 1.77 mu g nonanal dissolved in 25 mu l methylene chloride) attracted more beetles when applied in a white artificial flower than when applied in a white-yellow artificial flower from 40 cm distance. This finding may be helpful in the development of traps for pestmanagement strategies.