Unsaturated Cuticular Hydrocarbon Components of the Sex Pheromone of Eggplant Fruit Borer, Leucinodes orbonalis Guenée (Lepidoptera: Crambidae).

Leucinodes orbonalis is one of the most damaging insect pests affecting eggplant in the Mekong Delta of Vietnam. While (E)-11-hexadecenyl acetate (E11-16:OAc) and its alcohol, (E)-11-hexadecenol (E11-16:OH), have been identified as major and minor sex pheromone components, respectively, few males were attracted to a blend of these compounds in Vietnamese fields. In order to utilize synthetic pheromone of L. orbonalis as a tool for sustainable pest management programs, we reexamined the pheromone of this species in order to search for other minor components. Gas chromatography-electroantennogram detection and gas chromatography/mass spectrometry analyses of abdominal tip extract revealed the presence of two electroantennogram-active compounds, E11-16:OAc and (3Z,6Z,9Z)-3,6,9-tricosatriene (Z3,Z6,Z9-23:H) in a ratio of 100:2. An extract of the abdomen and thorax showed an additional electroantennogram-active component, (3Z,6Z,9Z)-3,6,9-docosatriene (Z3,Z6,Z9-22:H), with the three compounds (E11-16:OAc, Z3,Z6,Z9-23:H and Z3,Z6,Z9-22:H) being present in a ratio of 100:45:1, indicating that the trienes were mainly present on the cuticular surface. In the field, traps baited with E11-16:OAc and the C triene, in a mix of 10:1, caught more male moths than traps baited with the acetate alone. A field evaluation of other polyunsaturated hydrocarbons showed that the C triene found in body extract also increased catches when added to the acetate, but no other hydrocarbons did. In contrast, to other studies with this moth, the addition of E11-16:OH to E11-16:OAc plus the C or C triene, resulted in decreased trap catches.