Antennal and behavioral responses of female Maruca vitrata to the floral volatiles of Vigna unguiculata and Lablab purpureus

In many herbivorous insects, the attraction to suitable host plants is in partmediated by similar olfactory cues from different host plants. This study investigated the electrophysiological and behavioral responses of female Maruca vitrata Fabricius (Lepidoptera: Crambidae) to floral volatiles from two host plants, Vigna unguiculata (L.) Walpers and Lablab purpureus (L.) Sweet (both Fabaceae). Qualitative and quantitative differences were found between the odor profiles of two host plants by gas chromatography-mass spectrometry (GC-MS). Nine electroantennography-active compounds were detected in the headspace collections of the two host plants by means of coupled GC-electroantennographic detection. In a wind tunnel, female behaviors (upwind flight and source approach) were not affected by stimuli or their interaction with host plants, but the behaviors were influenced by host plants. A mixture of the nine bioactive compounds, including limonene, 1,3-diethylbenzene, benzaldehyde, acetophenone, 4-ethylbenzaldehyde, 1-(4-ethylphenyl)-ethanone, 2-methyl-3-phenylpropanal, 1H-indol-4-ol, and 1,1'-(1,4-phenylene) bis-ethanone mimicking L. purpureus (in a ratio of 0.4:9.7:2.4:5.7:78.1:4.8:100:0.6:30.3) attracted significantly more females approaching the sources compared with the mixture of compounds mimicking V. unguiculata (in a ratio of 0.3:1.4:1.6:3.7:50.8:3.2:100:4.2:16.7). Further bioassays revealed that a subtractive 4-component blend [limonene, 1,3-diethylbenzene, 4-ethylbenzaldehyde, and 1-(4-ethylphenyl)-ethanone in a ratio of 0.4:9.7:78.1:4.8] was essential for maximal attraction. Our study suggested that female M. vitrata might use similar odors from V. unguiculata and L. purpureus to locate suitable hosts and that an artificial lure, containing the major floral volatiles released by the two host plants, might be useful in exploring efficiency monitoring and/or control strategies of this moth in the field.