Bacteria Associated with some Dacus Species (Diptera: Tephritidae) and their Host Fruit in Queensland

Abstract

Over a period of 18 months the bacteria associated with approximately 70 adult flies of four Dacus species were isolated and identified. The flies were D. tryoni (Froggatt) and D. neohumeralis Hardy from guava (Psidium guajava L.), mulberry (Morus nigra L.) and peach [Prunus persica (L.) Batsch], D. cacuminatus (Hering) from wild tobacco (Solanum mauritianum Scop.), and D. musae (Tryon) from banana (Musa paradisiaca L.), and were collected in the field when these host plants were fruiting. All flies examined were surface-sterilized prior to aseptic dissection in which crop and mid-gut (stomach) or oesophageal bulbs were removed for culturing. Bacteria were also isolated from faeces of field-collected flies, as well as from host fruit surfaces, oviposition sites and larvae-infested tissue in host fruit. The predominant bacteria found in the alimentary tract of flies and in associated fruit specimens were members of the family Enterobacteriaceae. Klebsiella oxytoca, Erwinia herbicola and Enterobacter cloacae were the most frequently isolated species, with Serratia spp., Citrobacter jreundii, Proteus spp., Providencia rettgeri and Escherichia coli, being found less frequently. No one bacterial species was found to be consistently associated with anyone fly species. The bacterial species found most frequently in the alimentary tract were also found in large numbers on the surfaces of host fruit and in stung fruit.