A major host plant volatile, 1-octen-3-ol, contributes to mating in the legume pod borer, Maruca vitrata (Fabricius) (Lepidoptera: Crambidae).

Abstract

Previous studies on the legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of cowpea, Vigna unguiculata (L.) Walp. (Fabales: Fabaceae), in sub-Saharan Africa have focused on sex pheromones, but the role of the host plant on sexual behavior has not been explored. We investigated this interaction in the laboratory using behavioral assays and chemical analyses. We found that the presence of cowpea seedlings and a dichloromethane extract of the leaf increased coupling in the legume pod borer by 33 and 61 %, respectively, compared to the control, suggesting the involvement of both contact and olfactory cues. We used coupled gas chromatography-electroantennographic detection (GC/EAD) and GC-mass spectrometry (GC/MS) to identify compounds from the cowpea leaf extract, detected by M. vitrata antenna. We found that the antennae of the insect consistently detected four components, with 1-octen-3-ol identified as a common and dominant component in both the volatiles released by the intact cowpea plant and leaf extract. We therefore investigated its role in the coupling of M. vitrata. In dose-response assays, 1-octen-3-ol increased coupling in M. vitrata with increasing dose of the compound compared to the control. Our results suggest that the cowpea volatile 1-octen-3-ol contributes to M. vitrata sexual behavior.