Attractancy potential of bacterial volatiles from symbiotic bacteria of wild population of Zeugodacus cucurbitae Coquillett (Diptera:Tephritidae)

The melon fly, Zeugodacus cucurbitae (Diptera:Tephritidae) is one of the devastating pests of most cucurbits in India and its management by application of synthetic insecticides remained unsuccessful. Tephritid fruit flies are reported to harbour symbiotic microbiota in their gut and ovipositor, providing them nutritional resources in the ecosystem. The current study was carried out to isolate the symbionts and to test their attraction potential for trapping the melon fly adults. From the molecular analysis of 16S rRNA gene, 11 different species of bacteria were identified from gut and ovipositor of wild population of melon fruit fly. Among the identified bacteria, 7 species belonged to Enterobacteriaceae family, 2 species belonged to Bacillaceae family and one each belonged to Enterococcaceae and Flavobacteriaceae family. Among them Enterococcus faecalis, Citrobacter sp., E. meningoseptica, Klebsiella oxytoca, Bacillus amyloliquefaciens and Bacillus sp. were found only in ovipositor of the flies. Whereas, Raoultella ornithinolytica and Klebsiella sp. were found only in gut of the fruit flies. Two bacterial species, namely K. pneumoniae and E. cloacae were identified from both ovipositor and gut of wild flies. Five volatiles identified from these two bacteria were ammonia, dimethyl disulphide, methoxy phenyl oxime, 2, 2-dihydroxy-1-phenyl ethanone and butyl-2-methylpropyl ester of 1, 2-benzenedicarboxylic acid. The synthetic forms of identified volatiles and related compounds were tested for their potential to attract melon fruit fly. Ammonium hydroxide showed maximum attraction followed by iso amyl alcohol and dimethyl disulphide. Among the flies, 0–2 days old and 6–8 days old adults showed slightly higher attractancy towards the volatiles compared to 20–30 days old adults. Protein fed and protein starved adults showed maximum attractancy towards Ammonium hydroxide followed by Iso amyl alcohol. All the volatiles attracted more female flies compared to male flies.