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 doseresponse 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.
Effects of botanical extracts and formulations against fruit fly, fruit and pod borers on tomato and yard-long bean.
Seed kernel extracts of China berry (Melia azedarach) against oriental fruit fly (Bactrocera dorsalis) and tomato fruit borer (Helicoverpa armigera), and commercial neem formulations containing azadirachtin (Biofree-I® and Thai neem 111®) against the legume pod borer (Maruca vitrata) were tested in Taiwan and Thailand to confirm their effects on oviposition, feeding, growth and development. Various extracts from M. azedarach seed kernels significantly reduced the oviposition of B. dorsalis and the efficacy was similar to Biofree-I®. The green drupe and dry seed kernel extracts of M. azedarach substantially increased larval mortality, and reduced successful pupation, pupal weight, adult emergence, fecundity and egg hatch of H. armigera larvae. Commercial neem formulations exhibited adverse morphogenic effects on various biological parameters of M. vitrata, but they did not reduce oviposition and egg hatch. M. azedarach extracts and commercial neem formulations can be employed together for the sustainable management of B. dorsalis, H. armigera and M. vitrata.