Leaf Epicuticular Wax Chemicals of the Japanese Knotweed Fallopia japonica as Oviposition Stimulants for Ostrinia latipennis

Extraction, fractionation, and gas chromatography−mass spectrometry analyses guided by bioassays have shown that n-alkanes and free fatty acids in leaf epicuticular wax of the Japanese knotweed Fallopia (Reynoutria) japonica stimulate oviposition in the Far-Eastern knotweed borer, Ostrinia latipennis (Lepidoptera: Crambidae). n-Alkanes made up 48.1% of the total amount of epicuticular wax, and their carbon chain length was in the C₁₆−C₃₃ range, with n-nonacosane (n-C₂₉) most abundant, followed by n-C₂₇, n-C₂₅, and n-C₃₁. Free fatty acids with C₉−C₂₂ accounted for 22.3%, and hexadecanoic acid was predominant. A mixture of authentic n-alkanes and fatty acids of the composition found in the epicuticular wax, a mixture of n-alkanes, and a mixture of fatty acids significantly enhanced oviposition. Thus, it was demonstrated that both n-alkanes and free fatty acids in leaf epicuticular wax of F. japonica are naturally occurring oviposition stimulants for O. latipennis.