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 C23 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 C22 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 C22 or C23 triene, resulted in decreased trap catches.